Common Ragweed—Ambrosia artemisiifolia L.: A Review with Special Regards to the Latest Results in Protection Methods, Herbicide Resistance, New Tools and Methods

Abstract

Common ragweed (Ambrosia artemisiifolia L.) has been identified as one of the most harmful invasive weed species in Europe due to its allergenic pollen and competitive growth in diverse habitats. In the first part of this review [Common Ragweed—Ambrosia artemisiifolia L.: A Review with Special Regards to the Latest Results in Biology and Ecology], its biological characteristics and ecological behavior were described in detail. In the current paper, control strategies are summarized, focusing on integrated weed management adapted to the specific habitat where the species causes damage—arable land, semi-natural vegetation, urban areas, or along linear infrastructures. A range of management methods is reviewed, including agrotechnical, mechanical, physical, thermal, biological, and chemical approaches. Particular attention is given to the spread of herbicide resistance and the need for diversified, habitat-specific interventions. Among biological control options, the potential of Ophraella communa LeSage, a leaf beetle native to North America, is highlighted. Furthermore, innovative technologies such as UAV-assisted weed mapping, site-specific herbicide application, and autonomous weeding robots are discussed as environmentally sustainable tools. The role of legal regulations and pollen monitoring networks—particularly those implemented in Hungary—is also emphasized. By combining traditional and advanced methods within a coordinated framework, effective and ecologically sound ragweed control can be achieved.

1. Introduction

Common ragweed (Ambrosia artemisiifolia L.) (hereinafter referred to simply as ragweed) is one of the most widespread and problematic invasive weed species across Europe, including Hungary. Despite extensive Hungarian and international research and international projects, its importance has not decreased, and in fact, according to forecasts, it will not decrease, especially with regard to its pollen production in connection with climate change. In order to reduce its population, further biological and control technology research is necessary. In the latter case, the development of new, innovative procedures and their wider application in practice are especially necessary. Its rapid proliferation, substantial allergenic pollen output, and competitive ability make it a significant threat to agriculture, biodiversity, and public health. Ambrosia artemisiifolia L. is a summer annual (Therophyta, T4) and belongs to the family Asteraceae (Asterales). It spreads due to high seed productivity; the seeds are viable in the soil for more than 40 years. It has a very competitive and strong allelopathy effect [1]. The northward expansion is underway; therefore, an effective weed management strategy is needed to reduce the population in cultivated and non-cultivated areas. Herbicide resistance has progressively emerged as a significant issue over the years. Alternative protection solutions hold potential; however, successful outcomes necessitate the integration of conventional and modern technologies. The precision weed survey and control represent a novel approach that aids in minimizing ecological impact.

This review is based upon previous overviews and intends to integrate the most recent advances in biological control, herbicide resistance, and also the utilization of digital tools in precision weed management. It provides a comprehensive overview of the current ragweed control methods under cultivated areas, focusing on their mechanisms, effectiveness, advantages, and limitations. In our work, we specifically focus on biological control, herbicide resistance, precision agriculture technologies, and regulatory frameworks that influence the effectiveness of ragweed management. However, in contrast to earlier works that primarily focused on the ecological characteristics or chemical control of ragweed, our work particularly emphasizes a holistic approach that integrates agricultural, environmental, and technological perspectives; therefore, it provides a synthesis of scientific progress and practical implementation in diverse land-use systems.

In order to achieve the above mentioned goals, the major criterion in the selection of literature was to include in the review those scientific publications that are of practical relevance. In this review work, all currently prevailing control methods were taken into consideration; however, specific attention was paid to those applications that will most likely be dominant in the future.

Our work attempts to highlight that sustainable and successful suppression of common ragweed requires a shift from a reactive to proactive approach supported by ecological knowledge, resilient planning, and technological innovation. Most importantly, this review aims to support that transition by offering a comprehensive and practical synthesis of the latest research on ragweed control. While particular challenges remain, mostly regarding resistance, costly technologies, and biocontrol safety issues, the current state of the art reveals that there are existing opportunities to integrate these possible tools into reliably achievable, habitat-specific strategies in ragweed control practices.

2. Protection Methods Against Ragweed Under Cultivated Areas

Having outlined the biological and ecological significance of common ragweed, the following section focuses on the various control methods applicable in cultivated areas. Nonchemical (agrotechnical, physical, mechanical, heat and biological) and chemical methods of integrated weed management are discussed in detail.

2.1. Agrotechnical Protection

Agrotechnical weed management includes crop rotation, proper sowing time, row distance, plant number for a unit area, cover plants, mulching, crop cultivars with good competitive ability, and professional nutrient supply. Out of agrotechnical factors, the crop species and the crop cover are believed to be the most critical in affecting the ragweed cover [2]. Farkas [3] investigated the effects of various soil cultivation methods on ragweed. Based on her results, plowing is favorable for spreading ragweed. Aside from that, crop rotation should be planned to suppress ragweed, and the restriction factor of soil cultivation should be completed with chemical treatments, such as herbicides, to provide an efficient nutrient supply for the crop. Smaller row distance may be efficient for ragweed suppression in low-growth crops. Due to the improved weed suppression ability, the efficacy of weed control techniques is also better [4]. In areas with low crop cover, the ragweed cover is taller, especially at the edges of the fields [5]. In the case of early harvested crops (winter cereals, oilseed rape), proper stubble treatment (mechanical or physical, but chemical as well) is essential [6]. Rainfall, in addition to professional agrotechnology, is critical for crop development. Due to the lack of rain, the green biomass production of the crops will be lower, and the leaf area will not entirely cover the soil surface, so the crops’ competition ability will be reduced. Crop rotation is one of the most important factors in agrotechnical weed management. Winter cereals, perennial Fabaceae crops, and silage corn are characterized by good competition ability [7]. In cases where agrotechnical actions are insufficient, mechanical interventions provide an essential, although non-chemical, alternative for effective ragweed suppression.

2.2. Mechanical Weed Management

High-precision sensor-controlled devices and technologies will probably greatly reduce herbicide use. Mechanical weed management is a fundamental part of the non-chemical weed management methods and is generally used between the rows for weed control [8].

Based on Kismányoky’s [9] work, so-called minimum tillage resulted in the highest ragweed cover out of the tillage system. Recently, row cultivators with rubber fingers are becoming more common; these cultivators are very effective against the weeds in their early phenological phase [10]. Row cultivators can also be combined with sprayers (Figure 1) [11].

The optimal phenological phase for ragweed control is the cotyledonous-two-leaf stage (BBCH-10–12). Mechanical control can be more effective which using strategies such as cutting the roots and covering the plant parts with soil [12]. One of the mechanical strategies, hand weeding, can be effectively used in smaller areas and around populated ones where human resources are available. In the case of hand weeding, applying a protective glove is essential since contact between ragweed and human skin can cause an allergic reaction in people who are sensitive to it [13]. When mowing is applied too early, at the beginning of the vegetative phase, it triggers rapid regeneration of ragweed plants, producing more vegetative and generative biomass, including flowers and seeds [14]. Béres [15] and Basky [16] examined the effect of mowing time and frequency on the generative development of ragweed. Mowing in ruderal habitat two or three times can significantly reduce (by 93–98%) the number of flowers. A vital technological element is the stubble treatment, in which the aim is water conservation and reducing the number of weed seeds in the soil seed bank. Once mechanical stubble treatment is no longer enough for ragweed control, the soil-covered plants can regenerate; therefore, this intervention must be repeated [16]. Regarding mechanical weed control, weed combs also play an essential role in ragweed control. These comb harrows are working on removing the young seedlings (BBCH: 12–14) from the soil and later covering them with soil. Ragweed at the cotyledonous-4 leaf stage (according to the BBCH scale of 10–14) is very sensitive to soil cover [17]. Sunflower rows are commonly filled with soil when the sunflowers are more developed than the ragweed. Ploughing promotes the death of the seedlings by filling the soil in the row. Young ragweed seedlings will die if the covering soil layer is at least 6 cm thick [18].

2.3. Thermal Weed Control

In addition to physical methods, thermal techniques have also been explored as possible approaches against ragweed control.

Reisinger-Borsiczky [11] conducted weed control experiments on ragweed (Mosonmagyaróvár, Hungary). A 3-wheeled flamethrower powered by a special propane-butane gas cylinder was tested on a construction site disturbed by earthmoving machines, providing an ideal ragweed development environment. The effect of the flamethrower was examined by moving along the experimental area at different speeds. The change in the plant stands and the turgor loss were detected. But 14 DAT (days after treatments) later, independent of the treatment time, ragweed plants were able to regrow. As a result, it was determined that thermal eradication under such environmental conditions is insufficient for ragweed control.

2.4. Biological Weed Control

As chemical use is gradually being restricted, biological control methods, as environmentally friendly solutions, are gaining importance in integrated weed management.

The role of biological control is considered important in the control of weeds, especially invasive species. There are many herbicides available to control ragweed, but more and more are being withdrawn in the EU. Therefore, the role of non-chemical (including biological) methods will be increasingly valued in plant protection practice in the future. We must follow quarantine rules in developing biological weed control methods, especially for invasive alien species (IAS). Due to taxonomic proximity, biological agents against ragweed should not pose a threat to sunflowers. Biological methods combined with other technologies may be an efficient tool for ragweed control [13].

2.4.1. Viruses

Viral infections may also affect ragweed growth as potential elements of biocontrol strategies. Takács et al. [19] detected a lot of phytopathogen viruses from ragweed (Tomato spotted wilt virus, Cucumber mosaic virus, etc.). Although visible symptoms on ragweed were not observed, from a viral epidemiological standpoint, the infection can pose a significant risk, given that ragweed may be a latent host of both more viruses and their vectors. Hence, ragweed can be considered a primary infection source, playing a significant role in the epidemiology of economically important plant viruses [4].

2.4.2. Fungi

Pathogenic fungi are being investigated for their potential role in reducing ragweed populations. Didovich et al. [20] investigated the ragweed’s response to Stagonosporopsis heliopsidis Aveskamp (Pleosorales: Dydimellideae). According to the findings, this fungus killed 50% of the ragweed plants. Another fungus, Albugo tragopogonis Gray (Albuginales: Albuginaceae), that was isolated from ragweed considerably reduced the biomass production of the host plant. Based on Farr et al. [21], powdery mildew occurs on common ragweed, and Runion et al. [22] observed the perfect (Eryshiphe) and the imperfect (Oidium) forms on ragweed. Bohár [23] reported the occurrence of Puccinia xanthii Schwein (Pucciniales, Pucciniaceae) on living ragweed plants and herbarium samples. Still, it is known that this fungus cannot cause serious epidemics and cannot significantly reduce ragweed biomass production [24].

Kiss et al. [25] reported the considerable injurious effect of Plasmopara halstedii Berl. & De Toni (Peronosoprales: Peronosporaceae) on ragweed, causing a 90% pollen reduction. Unfortunately, this fungus is also a sunflower pathogen. Additionally, a lot of polyphagous pathogens are known to occur on ragweed, e.g., Sclerotinia sclerotiorum de Bary (Helotiales: Sclerotiniaceae), Botrytis cinerea Pers. Ex Nocca & Balb. (Helotiales: Sclerotiniaceae), etc. Bohár [26] observed typical Phyllacora ambrosiae Sacc. (Phyllachorales: Phyllachoraceae) phytopathogen fungi symptoms on ragweed both in Hungary and Ukraine. Ragweed is probably infected by polyphagous fungi belonging to the genera Fusarium, Aspergillus and Rhizoctonia. Although regular infestations only occurred in a few years, they were more common in humid and cool conditions [27]. Bipolaris sorokiniana (Sorokin) Shoemaker, 1959 (Pleosporales; Pleosporineae), Colletotrichum dematinum (Pers.) Grove, 1918 (Glomerellales; Glomerellaceae), Macrophomina phaseoline (Tassi) Goid., 1947 (Botryosphaeriales; Botryosphaeriaceae,) Rhizoctonia Solani J.G. Kühn, 1858 (Cantharellales; Ceratobasidiaceae), Septoria epambrosiae D.F. Farr, 2001 (Mycosphaerellales: Mycosphaerellaceae), Synchtrium macrosporum Karling, 1957 (Synchytriales: Synchytriaceae) were also detected on ragweed plants [28].

2.4.3. Insects

Based on the known related sources, effective biological methods against ragweed are not yet available. In addition to birds and rodents, generalist insects (Coleoptera, Lepidoptera, Hemiptera, and Hymenoptera) also reduce the number of A. artemisiifolia seeds [29]. The insects feeding on ragweed are considered to be natural enemies in the gene centre [Zygogramma suturalis Fabricus (Col.: Chrysomelidae), Tarachidia candefacta Hübner (Lep.: Noctuidae), Ophraella communa LeSage (Col.: Chrysomelidae)] [6]. Earlier, Reznik et al. [14] and Szigetvári-Benkő [30] stated that Z. suturalis is a prominent insect in ragweed biological control. The species belongs to the leaf beetle family, which has two generations within a year. The larvae of the first generation can appear from the middle of May until the beginning of June. The second generation begins to develop at the end of summer in its native distribution area, e.g., Ohio [31]. A relatively low adaptation ability to low temperature can characterize this beetle species; the survival rate of the adults is between 11.9–31.1% after stored on 4–6 °C for 57–146 days. Therefore, it cannot be applied in cold ecological conditions, according to Wan et al. [32].

Epiblema strenuana Walker (Lep.: Tortricidae) was introduced to Croatia and China for the biological control of ragweed. Despite the successful settlement, ragweed populations could not be reduced effectively. The larvae mine in the ragweed leaves and later feed on the stems; when faced with these damage characteristics, ragweed plants develop shorter internodes. The larvae and adults of O. communa feed on the leaves and shoots of ragweed. The combined utilization of these two bio-agents can be a perspective and sustainable solution against A. artemisiifolia in the near future because they have an additive effect, and due to their different feeding places, they are not competitive with each other. E. strenuana delays the early development of ragweed; this gives O. communa the opportunity to synchronize its mass emergence with the period of peak green mass of its host plant [33]. Iqbal et al. [34] examined the possibilities of biological control against A. trifida Linné (Asterales, Asteraceae) and A. artemisiifolia. Biocontrol agents were Puccinia xanthii, E. strenuana, and Solenopsis invicta Buren (Hymenoptera, Formicideae). Puccinia xanthii and E. strenuana could cause a considerable biological decline in A. trifida. Solenopsis invicta significantly reduced ragweed development due to root injury but may also negatively affect sunflowers.

Among the insects, O. communa is in the research focus, and studies suggest that it has the potential to control ragweed. It is native to North America, belongs to the family Crysomelidae, the Galeucinae subfamily, and the tribe Galericini. In Europe, some of the native species can be easily distinguished with O. communa: Phyrrhalta joannis, Xanthogaleurca laboissiére and the species of Gallerucella genus [4,35,36].

This insect can destroy ragweed before it flowers. In areas where temperatures are extreme, the chances of the insect colonizing are limited. In areas where temperatures are low, it cannot destroy the ragweed before flowering (Northern limit 46–48° north latitude). Conversely, in areas where the temperature is above average (tropical zone), its development will be accelerated and its survival rate will be very low [4,35]. Ophraella communa will not be able to destroy its host plant in time and to a sufficient extent in all new habitats, A. artemisiifolia. Still, it can be characterized by a great deal of genetic variability, which provides adaptation to extreme meteorological conditions and could reduce the ragweed population before flowering [35]. The larvae can reduce ragweed pollen production by 82%, O. communa was detected on all ragweed individuals. The beetles are capable of causing significant reduction of the green biomass of ragweed, even before flowering. It was found that O. communa does not cause substantial injuries to sunflowers [36], and insects are dependent on A. artemisiifolia for population survival [37].

Ophraella communa was first detected in Europe in 2013 (Switzerland). After the destruction of ragweed populations, they did not cause considerable injuries to other host plant species. In young ragweed seedlings, one adult can destroy one ragweed plant, while in older plants (characterized by a 90–100 cm plant height), 12 adults are necessary to cause ragweed death [34]. Augustinus et al. [38] reported the occurrence of beetles in the Valtelinean region of North Italy. The spreading of O. communa can be presumed in the Rhone valley regarding the large ragweed populations of ragweed exists in this region [39]. Ophraella communa was an introduced invasive beetle in Slovenia, Croatia, and northern Italy [40,41]. Karrer et al. [42] reported new habitats regarding the beetle’s new area, 35 km from Ljublana. It spread from Zagrab to the southeastern parts of the country. It was discovered for the first time in Romania (Bucharest) in 2020, and later, in areas of north Bosnia and Herzegovina. The short-distance spreading is due to the good flying ability, while transmission for longer distances is due to international trade and transport (Figure 2). Petrović-Obradović et al. [43] reported its first occurrence in Serbia. The Beetle was registered in Belgrade and appeared to be associated with international transportation. Horváth-Lukátsi [44] reported its occurrence in Hungary (Soroksár, next to Budapest). Regarding the fact that they found a relatively low population of O. communa (along the M5 highway), it was presumed that the beetle could be introduced in the country with the help of international transport.

In Japan (Tsukuba district), overwintering images are copulated, and after that, female individuals lay eggs from the end of April until May. The full adults appear in June and July months; due to the overlapping of the generations, all developmental stadiums of the pest are present at the same time. The third generation will be developed after August when a part of the adult group enters into dormancy (diapause), while others continuously develop, and a fourth generation will also be observed [45].

Figure 2. European spreading of O. communa (A) and the observation frequency of the insect (B). source [46].

Figure 2. European spreading of O. communa (A) and the observation frequency of the insect (B). source [46].

According to Keszthelyi et al. [46] scenarios, the theoretical border of the annual life cycle is in the southern part of the North latitude between 46 and 48°, and the northern part of the North latitude between 55 and 60°. In the warmer habitats (e.g., India, the Indochinese Peninsula), 9–10 generations could be developed. Under the moderate climate in Europe (North Italy, Croatia, and Slovenia), this pest has 2–3 generations. Four generations could be developed in the northern Balkans (including Hungary). In the future, they are predicted to spread to the northern parts of the EU; they can already be found in Germany and Poland. The 48–49° latitude marks the northern limit of its range. The actual climate scenario indicates the northern spread of ragweed, potentially spreading to the northern parts of the Scandinavian region by the second half of the century. Similar to ragweed, the spreading of its biocontrol agent, O. communa, toward the north can also be detected. In other words, the bioagent follows the escalation of its primary host plant. The biological and ecological characteristics of the two species (ragweed and the beetle) are similar. However, ragweed will probably continue to spread in areas that are unfavorable for the beetle. Due to this, the O. communa could not be an efficient control against it in those areas [47].

However, after settlement in the new habitats of some invasive species, the introduction of its natural enemies was a good option, assuming the latter could adapt to the new conditions. One example is the introduction of Diorhabda carinulata Desbrochers (Colepotera: Crysomelideae); after the settlement of the invasive Tamarix spp. in North America, the insect was able to widen its ecological amplitude [48]. O. communa male and female imagoes were stored under the cold tolerance threshold for 8 days. The glycerin content of the new female generation was enhanced by 32%, so the specimens of the new generation showed higher tolerance to the low temperature. As a conclusion, we can state that O. communa has been characterized with a good adaptation ability to the cooler climate regions [36]. Keszthelyi et al. [46] proved that the dominant wind direction is a significant factor in the spread of O. communa. Schaffner et al. [49] stated that O. communa could reduce the examined area. In case of biological weed control, the natural enemies of the invasive weeds may also greatly injure the non-target plant species, so it is vital to study the effect of bioagent on the non-target species also [50]. Before introducing an invasive bioagent, it is very important to detect the negative effects on the non-target species (direct or indirect). More research is necessary to evaluate the risk factors, with special regard to the non-target plant species [51]. O. communa uses its special olfactory receptors to identify the host plant. The bioagent can detect the host plant when the visual weed survey does not give sufficient data regarding the ragweed’s presence due to the sunflower’s low row distance [52]. Dernovici et al. [53] stated that the beetle can greatly injure sunflowers if the main host (ragweed) is not present. However, 60% of the female individuals of the beetle died within 30 days. Only 14% of the female individuals died when grown on ragweed as a host plant. Individuals feeding on ragweed could produce more eggs (0.4 eggs/day), and 86.7% of the eggs produced viable young beetles. The beetle populations feeding on ragweed increased 208 times over 30 days, while those populations feeding on sunflowers decreased by 4.2%. The future spread of O. communa in Europe is forecasted.

Regarding the fact that Hungary has large populations of ragweed, the further distribution of the ragweed beetle can be presumed. Kontschán et al. [54] reported new locations of its appearance in Budapest, Fót, and Vecsés. So far, its habitat has only been reported in rural areas and township districts, and it has not yet been detected on arable fields, where ragweed is the most widespread weed. Iványi et al. [55] studied the establishment of O.communa at six different climatic locations in Hungary, examining the ability of the insects to colonize all the sites studied, but the rate of population establishment varies considerably. Beetles colonized Asian continents such as China, Korea, Japan, and Taiwan [56,57,58,59]. Tian et al. [60] stated they adapt rapidly to the lower temperature, and this makes it possible for them to be a potential bioagent against ragweed even in cooler climatic regions. Nonetheless, it should be noted that, after significant O. communa damage to ragweed, ragweed specialist pests can also be found in ragweed’s natural habitats [48].

In summary, O. communa is a potential bio agent to control ragweed; it can effectively reduce the assimilation interface (up to 80%), pollen production and seed production by 70–80% of A. artemisiifolia. Ophraella communa is spreading by following its hostplant northwards, and the wind has a key role in spreading of the insect. The research shows that non-target species, especially sunflower, can only be damaged by O. communa when the host plants are destroyed and there is no more ragweed nearby. When O. communa feeds on sunflower, its survival rate is reduced and its reproduction is harmed. There is a small risk to becoming a potential pest in sunflowers, but this can only be the result of a long process. It is obvious that O. Communa is an effective bioagent in ruderals and non-cultivated areas. However, it is not clear how the population is growing in insecticide-treated crops.

Other observations have been made related to polyphagous herbivores, but there is not much hope for the perspective use of these insects against A. artemisiifolia due to their biological features (not closely related to this food plant). Horváth et al. [61] proved that Coniocleonus nigrosuturatus (Goeze (Col.: Curculionidae) is believed to be a natural enemy of ragweed. Because this insect can destroy ragweed populations, it could be considered a potential bioagent. Nonetheless, more research is needed to prove its viability on other host plants (sunflower, soybean, maize, and sugar beet). Kiss [62] found a lot of polyphagous insects on ragweed. In 2005 (in Tapolca-Diszel, HU), after the autumn plowing of a field used as pasture for many years, a large population of Longitarsus pellucidus Foudras (Colepotera: Crysomelideae) was detected. Later, the insect was found in more fields, and they proved that five adults on a young ragweed plant (BBCH:12–13) could cause considerable biological decline of ragweed. The presence of Agapanthia dahli Richter (Coleoptera: Cerambycideae) feeding on young ragweed plants was discovered in 2010. This pest caused stem mining [4]. However, this pest is unsuitable as a biocontrol agent as it can damage sunflowers as well. Basky [63] studied the harmful effect of aphids on ragweed. Out of the pests, Brachycaudus helichrysi Kaltenbach (Hemiptera: Aphididea) was the dominant aphid species, causing considerable distortion and chlorotic spotting on ragweed leaves. Aphys fabae Scopoli (Hemiptera: Aphididea) occurred less frequently and formed larger colonies on only a few plants (Figure 3).

Myzus persicae Sulzer (Hemiptera: Aphididea) was the rarest aphid species on ragweed, never forming large colonies. Magyar-Basky [64] later studied other endemic aphid species on the ragweed. Artificial aphid infestation of ragweed (A. fabae, B. helichrysi) under glasshouse conditions significantly reduced plant height, shoot dry matter, flower length, inflorescence axis, number of male flowers, and pollen production. Csóka [65] described the Helicoverpa armigera Hübner (Lepidoptera: Noctuideae) as a pest of ragweed.

2.5. Chemical Weed Control

The herbicide application technology can be various, depending on the herbicide type. The preplanting (presowing) technology can be a soil herbicide (which may be lightly worked into the soil and is good against weeds emerging from the top layer of soil) or a non-selective foliar herbicide against weeds that have already emerged. The pre/post technology is used when the weed seeds have already emerged, but the crop has not yet germinated. This application generally can be done with glyphosate, but it is important that the soil humus content is at least 3% and the crop seed is covered with at least 3 cm of soil. In preemergent weed control, the herbicide is applied after sowing but before the crop and weeds germinate. In this technology, precipitation is essential, requiring 10–20 mm within 2 weeks. In preemergent weed control technology, root herbicides are mainly applied. This technology is only effective on weeds that emerge in the 3 cm topsoil layer. Postemergent herbicides are mainly leaf herbicides. This active ingredient has the best efficacy when the annual dicot weeds (like ragweed) are between the cotyledon-2 true leaf stage (annual monocot weeds in the root change stage) [66].

Despite the growing interest in alternative methods, chemical control remains widely applied and, to date, it is the most effective control strategy. It has a lot of advantages, e.g., good effectivity, low cost, etc. However, in integrated weed management, alternative (non-chemical) methods are preferred. In large-scale farming (especially in arable fields), the use of herbicides cannot be avoided. To avoid early weed infestation, we can use preplant treatments, but to ensure the ragweed infestation halts later, we must apply pre- and postemergence treatments [66]. In the case of preplant one, this occurs before crop sowing herbicides are applied [67]; in the pre-plant “burndown” technologies, glyphosate and/or 2,4-D active ingredients are generally used. Several efficient and cheap herbicides are available for ragweed control in monocot crops like cereals and maize [68]. The sensitivity of ragweed to 2,4-D and glyphosate herbicides increases as the ambient temperature increases [69]. Glyphosate is thought to be the most commonly used herbicide for ragweed control. Based on Chandi et al. [70], although glyphosate-resistant cultivars and hybrids of soybean and maize are grown worldwide (GMO plants are not permitted in HU), glyphosate-resistant ragweed biotypes have already been discovered [71]. Barnes et al. [72] examined different alternative methods against ragweed in the case of HT (herbicide-tolerant) soybean biotypes. It is based on the fact that PP herbicides have an anti-ragweed effectiveness of more than 90%. The combination of chlorimurom-ethyl, flumioxazin, and tifensulfuron-methyl had the lowest efficacy (52%). Treatments containing glufosinate, paraquate, 2,4-D, imazetapir, chloransulam, and flumioxazine ingredients were 90–99% effective against ragweed. Saflufenacil showed moderate effectivity (75%). Nedelcu et al. [73] tested foramsulfuron + jodosulfuron-methyl-Na, bromoxinil + 2,4-D, tembotrion + izoxadifen-ethyl, and terbuthylazine + bromoxinil against ragweed at three and ten leaf stages (BBCH: 13–18). The application of the foramsulfuron + jodosulfuron + methyl Na combination resulted in 80% efficacy (at the phenological phase of ragweed at 3–4 leaf stages); in 5–6 leaf stages, the same treatments resulted in a lower 71% weed control efficacy, and in 8–10 leaf stages, only 48.7% efficacy was achieved. Stef [74] investigated the ragweed control effects of dimethenamid-P, dimethenamid-P + pendimetalin, S-metolachlor + terbutilazine, and S-metolachlor in sunflowers. The best weed control effect was achieved by combining dimethenamid and S-metolachlor, which produced a 98.4% efficacy for ragweed control. The combination of S-metolachlor and terbuthylazine was also effective, with a 92% efficacy against ragweed. S-metolachlor alone had a 72% efficacy, while dimethenamid-P had an 80% efficacy. Týr et al. [75] studied the efficacy of two preemergent herbicides (dimethenamid and fluorochloridone) and three postemergent treatments on ragweed in maize (mesotrione, dicamba, and rimsulfuron). They demonstrated that the basic (pre) treatments outperformed the post treatments in terms of ragweed control efficacy.

Ragweed control is a significant problem in sunflowers because the taxonomic relationship of the two species results in similar reactions to herbicides [76]. The herbicide combinations generally provide better efficacy against ragweed than one herbicide alone. We must pay special attention to the proper dosages in the case of three-component combinations. This can be achieved by engaging the services of a professional plant doctor, as the possibility of phytotoxicity can be greatly enhanced due to overdosage and improperly selected ingredients. According to Kádár [77], pretreatments are more effective than posttreatments. According to Týr et al. [75], at least 20–30 mm precipitation 5–10 DAT (days after treatment) is required for proper pretreatment efficacy. Fluorochloridone and oxyfluorfen can cause phytotoxic symptoms, such as yellowing and growth reduction, in sunflowers, although the plants later recover without a considerable yield loss. Applying bifenox and oxyfluorfen to well-cultivated soil with a smooth surface is essential because these herbicides can create a film layer on the soil surface [13]. The breeding of herbicide-tolerant (IMI) sunflower hybrids opened a new era in sunflower production. The resistance was introduced into sunflower lines via pollen from wild sunflowers. Imidazolinone resistance is ensured by the IMR1 gene and an extra-mitochondrially inherited accessory gene (IMR2). Pinke-Karácsony [78] reported that the ragweed cover is approximately 10% on sunflower stands in Hungary. Based on the work of Kolejanisz et al. [79], the highest cover (6.665%) was achieved by ragweed under arable conditions. In Austria, it has taken second place in terms of the weed cover (4.585%). In IMI sunflower hybrids, good efficacy can be achieved against ragweed (almost 100%) [80].

Although imazamox causes a temporary phytotoxic symptom on sunflowers (yellow flash) (Figure 4), the plant can tolerate it without experiencing considerable yield losses. In addition to the IMI sunflower, there are tolerant sunflower hybrids against the tribenuron-methyl ingredient (SU sunflowers). This active ingredient also has good efficacy against ragweed plants at the early stages (maximum until the 2–4 leaf stage). Primary weed control treatment is critical to avoid an early ragweed infestation [81]. Ragweed-free sunflower stands can be grown alongside SU and IMI sunflower hybrids. Under unfavorable climatic events, herbicide phytotoxicity can occur in sunflower hybrids [82].

It is very important to ensure the weediness of the sunflowers during the whole vegetation period. Strong weed infestation makes harvest more difficult (and sometimes impossible). This is especially true for the strong infestation of summer annual weed species, including ragweed. These weeds can outgrow sunflowers in the last two months of growth (Figure 5), producing significant biomass, shown in the experiments of Dávid-Kovács [83].

S-metolachlor+linuron, dimethenamid+imazamox, and S-metolachlor+oxyfluorfen combinations provided good efficacy in sunflowers. Regarding halauxifen, it can be used successfully in sunflowers up to 30 cm tall and also on non-HT hybrids. The herbicides that can be used in Hungary against ragweed in sunflowers are listed in

Table 1. Herbicides used in sunflowers against ragweed (source: Kádár [84]; https://novenyvedoszer.nebih.gov.hu/Engedelykereso/kereso, assessed on 17 July 2025).

Active Ingredient	Sensitivity of Ragweed 1	Application Time
fluorochloridone	8	PPI, Pre
flumioxazin	7	Pre, post
metobromuron	6	Pre
haluxifen-methyl (not in just HT hybrids)	9	Post
imazamox (IMI sunflower)	8	Post
tribenuron-methyl (SU sunflower)	8	Post
tribenuron-methyl + thiensulfuron-methyl (SU sunflower)	8	Post
glyphosate	9	Desiccation

¹ Sensitivity of ragweed to the herbicide (6 = less effective 75–89%, 7 = good effective 90–94%, 8 = very good efficacy 95–98%, 9 = excellent efficacy 99–100%).

.

Almost 9% of the weed cover in maize is due to ragweed [85]. Since the row distance in maize is relatively large, ragweed has enough space to grow. Since the 1950s, atrazine has been the dominant herbicide for maize. Maize is superselective to atrazine. it can biochemically detoxify the active agent through glutathione conjugation (physiological selectivity). However, due to the unilateral use of atrazine, resistant biotypes of some weeds, such as A. artemisiifolia, Chenopodium spp., and Amaranthus spp., evolved. This situation required the introduction of new herbicides in the maize weed control program. In maize, the harmful effect of monocot weeds is a real threat, but that of ragweed also cannot be neglected [80]. In maize, a wide range of weed control options regarding application time (PPI, pre, pre/post, post) and herbicides with as much as two months of effectiveness are available. Pretreatments have the best efficacy against weeds, while posttreatment effectiveness is relatively lower [74]. There are naturally evolved and selected herbicide-tolerant hybrids in maize from among the IMI tolerant, which are relevant considering ragweed control [79]. Herbicide-tolerant genetically modified varieties are also available; GM plant production is cultivated in very large areas in the USA, Argentina, and Brazil [86]. The herbicides that can be used in Hungary against ragweed in maize are listed in

Table 2. The applicable herbicides in maize against ragweed with a herbicidal activity greater than 75% (source: Kádár [84]; https://novenyvedoszer.nebih.gov.hu/Engedelykereso/kereso, assessed on 17 July 2025).

Active Ingredient	Sensitivity of Ragweed 1	Application Time
isoxaflutole + cyprosulfamide	9	PP, Pre, Post
florasulam + mesotrion	8	Pre, Post
isoxaflutole + thiencarbazone-methyl + cyprosulfamide	9	Pre, Post
mesotrion	7	Pre
sulcotrion + terbuthylazine	8	Post
sulcotrion	8	Post
mesotrion + piridate	7	Post
flufenacet + terbuthylazine	6	Post
florasulam + fluroxipir	7	Post
2,4-D	7	Post
2,4-D + dicamba	8	Post
bentazon + dicamba	9	Post
dicamba	9	Post
dicamba+nicosulfuron + prosulfuron	8	Post
florasulam + 2,4-D	8	Post
floramsulfurom + izoxadifeni-ethyl	9	Post
floramsulfurom + izoxadifen-ethyl+iodoszulfuron-methyl-Na	9	Post
foramsulfuron + thiencarbazone-methyl + iodoszulfuron+cyprosulfamide	9	Post
clopyralid	8	Post
foramsulfuron-Na + thiencarbazone-methyl + cyprosulfamide	9	Post
clopyralid + picrolam	9	Post
mesotrion + dicambaa	9	Post
mesotrion + dicamba + nicosulfuron	8	Post
mesotrion + nicosulfuron	6	Post
mesotrion+nicosulfuron + prosulfuron	8	Post
mesotrion + nicosulfuron + rimsulfuron	6	Post
mesotrion + terbuthylazine	8	Post
thifensulfuron	7	Post
nicosulfuron + dicamba	9	Post
nicosulfuron + rimulfuron + dicamba	8	Post
prorsulfuron	9	Post
pyridatee	6	Post
prosulfuron + dicamba	9	Post
rimsulfuron + dicamba	8	Post
tembotrione + izoxadifen-ethyl	9	Post
tembotrione + thiencarbazone-methyl + izoxadifen-ethyl	9	Post
thifensulfuron-methyl	7	Post
tritosulfuron + dicamba	8	Post
glyphosate	9	Desiccation

¹ Sensitivity of ragweed to the herbicide (6 = less effective 75–89%, 7 = good effectivity 90–94%, 8 = very good effect 95–98%, 9 = excellent efficacy 99–100%).

.

In sweet corn, few herbicides can be used because of its higher sensitivity and the long food health waiting time of some herbicides.

The weed flora of soybeans is similar to that of other row crops. Out of the hardly controllable dicot annual weeds, special attention should be paid to ragweed. It can survive the pretreatments and cannot be easily controlled through posttreatments [87]. The herbicides that can be used in HU against ragweed in soybeans are listed in

Table 3. The applicable herbicides in soybean against ragweed with a herbicidal activity greater than 75% (source: Kádár [84]; https://novenyvedoszer.nebih.gov.hu/Engedelykereso/kereso, assessed on 17 July 2025).

Active Ingredient	Sensitivity of Ragweed 1	Application Time
dimethenamid-P + pendimethalin	6	Pre
flumioxazin	6	Pre
clomazone	6	Pre
metribuzin	6	Pre
metobromuron	6	Pre
Bentazon + imazamox	8	Post
imazamox	8	Post
thifensulfuron-methyl	7	Post

¹ Sensitivity of ragweed to the herbicide (6 = less effective 75–89%, 7 = good effect 90–94%, 8 = very good effect 95–98%, 9 = excellent weed control efficacy 99–100%).

. According to [78], ragweed with a cover of 1.479% is the second most frequently found weed species for soybeans after Chenopodium album (1.718%). In soybeans, the weed flora is determined by the applied control techniques in the pre-crop. Soybeans cannot be maintained with a weed-free status until the end of the growing season using only chemical means [88]. Genetically modified glyphosate-resistant soybean is widely grown on the American continent, but glyphosate-resistant ragweed biotypes have recently been discovered.

Ragweed is one of the sugar beet weeds that can be problematic, and the herbicides generally applied for dicots can be phytotoxic to sugar beet. Hence, the optimal time for weed control should be chosen according to the meteorological factors, the phenophase of sugar beet, and the health conditions of the plants [84]. Clopyralid, chloridazon + quinmerac, phenmedipham, desmedipham, ethofumesate + lenacil, phenmedipham, desmedipham, and ethofumesate + lenacil are among the herbicides approved for ragweed control in sugar beet.

Based on the 6th National Weed Survey in Hungary, in the cereals, ragweed ranks second regarding the dominance order, with a cover of 1.53% of the weeds [84]. Its dominance may be relevant in seeded, incompletely germinated winter cereals and spring-sown crops [4]. Ragweed, grown on cereal stubbles, can occur in a carpet-like mass. In such cases, a correlation could be revealed between the weed density and the biomass production. Ragweed individuals reach their maximum weight at 24 individuals per square meter. At higher weed densities, due to intraspecific competition, biomass production for a unit area decreased [89]. In autumn-sown crops, like oilseed rape and winter cereals, ragweed emerges and causes significant damage to the crops, even in autumn, although it can survive until the first frosts. In grains, many effective herbicides are available for ragweed control. The herbicides that can be used in HU against ragweed in cereals are listed in

Table 4. The applicable herbicides in cereals against ragweed with a herbicidal activity greater than 75% (source: Kádár [84]; https://novenyvedoszer.nebih.gov.hu/Engedelykereso/kereso, assessed on 17 July 2025).

Active Ingredient	Sensitivity of Ragweed 1	Application Time
metsulfuron-methyl + tifensulfuron-methyl	8	autumn post
flufenacet + metribuzin	6	autumn post
flumioxazin	6	autumn post
diflufenican + metsulfuron	7	autumn post
2,4-D	8	spring post
2,4-D + dicamba	9	spring post
MCPA	8	spring post
florasulam + 2,4-D	8	spring post
florasulam + 2,4-D + aminopyralid	9	spring post
amidosulfuron + iodosulfuron + mefenipir-diethyl	9	spring post
aminopyralid + florasulam	8	spring post
aminopyralid + florasulam + cloquintocet-mexil + pyroxsulam	6	spring post
bifenox + mecoprop-P	9	spring post
diflufenican + florasulam	6	spring post
dicamba	9	spring post
dicamba + 2,4-D	9	spring post
dicamba + tritosulfuron	9	spring post
dichlorprop-P	8	spring post
dichlorprop-P + MCPA + mecoprop-P	9	spring post
florasulam	7	spring post
florasulam + fluroxypyr	6	spring post
florasulam + haluxifen-methyl	9	spring post
florasulam + haluxifen-methyl + piroxsulam	9	spring post
florasulam + cloquintocet-mexil + pinoxaden	6	spring post
florasulam + metsulfuron-metil + tribenuron	9	spring post
florasulam + tribenuron-methyl	8	spring post
florasulam + tritosulfuron	7	spring post
fluroxipir + clopyralid + MCPA	9	spring post
fluroxipir + metsulfuron-metil + tribenuron-methyl	9	spring post
fluroxipir + metsulfuron	7	spring post
fluroxipir + metsulfuron + thifensulfuron-metil	8	spring post
mecoprop-P	9	spring post
iodosulfuron + mefenpir-diethyl + thiencarbazon-methyl	6	spring post
clopyralid	8	spring post
cloquintocet-mexil + pinoxaden + piroxsulam		spring post
metsulfuron-methyl	7	spring post
pyraflufen-ethyl	6	spring post
metsulfuron-methyl, tribenuron-methyl	9	spring post
thifensulfuron-methyl + tribenuron-methyl	7	spring post
tribenuron-methyl	7	spring post
tritosulfuron	7	spring post
glyphosate	9	PP, stubble treatment

¹ Sensitivity ragweed for the herbicide (6 = less effect 75–89%, 7 = good effect 90–94%, 8 = very good effect 95–98%, 9 = excellent weed control efficacy 99–100%).

.

Ragweed can coexist with other summer annual weeds, like Amaranthus and Chenopodium species in potatoes, particularly on sandy, light soils, and it can make the harvest more difficult [68]. Since the number of herbicides approved for potatoes is relatively low, ensuring that potatoes remain weed-free is a great challenge [13]. The formation of primary and secondary ridges during potato cultivation significantly impacts the weed flora. After these, only herbicides can ensure weed-freeness. In general, potatoes have good weed-suppressing abilities. Thus, an essential criterion for successful weed control is to protect the crop against pests, such as the potato beetle (Leptinotarsa decemlineata), and pathogens (Phytophtora infestans) [77]. The application of fluorochloridone may cause intervascular chlorosis of potato leaves, especially on the sensitive cultivars, but symptoms cannot be detected later on the newly developed leaves. Weed control in potatoes is generally based on metribuzin, an asymmetric triazine derivative. Still, on some potato cultivars, like White Lady, Balatoni Rózsa, Démon, etc., it can cause phytotoxic injuries. The efficacy of metribuzin can decrease in arid conditions [13]. Fluorochloridone and rimsulfuron herbicides cannot be used in seed tuber production because these can reduce the shooting of vegetative buds and produce virus-like symptoms. The herbicides that can be used in HU against ragweed in potatoes are listed in

Table 5. The applicable herbicides in potato against ragweed with a herbicidal activity greater than 75% (source: Kádár [84]; https://novenyvedoszer.nebih.gov.hu/Engedelykereso/kereso, assessed on 17 July 2025).

Active Ingredient	Sensitivity of Ragweed 1	Application Time
fluorochloridone	8	Pre
flumioxazin	7	Pre
metobromuron	6	Pre
prosulfocarb	6	Pre
clomazone + metribuzin	7	Pre
glyphosate	9	Pre/post
metribuzin	6	Pre, Post
prosulfocarb + metribuzin	7	Pre, Post
pyraflufen-ethyl	8	Desiccant

¹ Sensitivity of ragweed to the herbicide (6 = less effect 75–89%, 7 = good effect 90–94%, 8 = very good effect 95–98%, 9 = excellent effect 99–100%).

.

Ragweed does not cause significant damage to peas due to its early sowing and early closing stock. However, due to the early removal of green peas from the field, attention should be paid to stubble management. Clomazone is an option as pretreatment, while bentazone, imazamox and MCPB are effective against ragweed as posttreatments.

Ragweed is also a relevant weed species in the fields where pepper and tomatoes are grown. Only a few herbicides are allowed in these vegetable crops. In pepper clomazone, in tomato metribuzin and rimsulfuron, are available for ragweed control. We must choose an area for production where serious, difficult weeds cannot be detected. Due to the late sowing (or planting), the emerging weeds can be destroyed with the soil cultivation. The weed control of ragweed should be done in the forecrop or on the stubble of the forecrops. Weed control between the rows can be solved using a cultivator, while within the rows, hand weeding may be necessary 2–3 times within a vegetation period.

Because the crop is sown in narrow line spacing, ragweed is not considered a dominant weed species of oilseed rape. In the case of rape, which is characterized by a wider line spacing, the occurrence of ragweed is more general. Ragweed can cause significant damage during the early competition with crops (winter cereals and rape) recently, with a close correlation to climatic change. This it underlines the necessity of autumn weed control. For postemergent treatments in rape, we can use the herbicides clopyralide, picloram + clopyralide + aminopyralid. Metazachlor + dimethenamid-P, metazachlor + dimethenamid-P + quinmerac, and pethoxamid + picloram combinations are effective as pretreatments against ragweed. Ragweed can also occur in large numbers in spots due to internal water or freezing. Growing IMI rape hybrids and cultivars has also been permitted recently.

In plantations (including fruits and vineyards), we use herbicides only for row treatments. Between the rows, non-chemical treatments are used, including regular mowing, living and dead mulch, grassing, and mechanical soil cultivation. Ragweed can be a serious problem in plantations (Figure 6), especially in younger ones. Here, only mechanical weed control methods are applied. In the first year after settlements, weed control against ragweed is based on mechanical methods (hoeing, row cultivation) [68,90]. Row mulching can also be used against ragweed, but it is not advisable in mountainous areas sensitive to soil erosion. As the plantation ages, a wider range of herbicides can come into the hands of the growers. Pendimethalin can be applied to plantations as early as the first year, while flazasulfuron and flumioxazine can be applied as early as the second year. When the plantation is three years old, we can apply glyphosate, and fluroxypyr against ragweed. The glyphosate + MCPA combination can be used starting in the fourth year of the plantation’s life [91].

In the vineyards, the combination of flazasulfuron and glyphosate is widely used. This practice resulted in the appearance of glyphosate- and flazasulfuron-resistant biotypes of Conyza canadensis in Hungary as well. For similar reasons, glyphosate-resistant biotypes of ragweed can occur in the future [92]. So far, this has not been proven in dose-response experiments in the Hungarian ragweed populations [93]. Recently, the application of a bioherbicide (pelargonic acid) was allowed. The herbicides that can be used in Hungary against ragweed in plantations are listed in

Table 6. The applicable herbicides in plantations against ragweed with a herbicidal activity greater than 75% (source: Kádár [84]; https://novenyvedoszer.nebih.gov.hu/Engedelykereso/kereso, assessed on 17 July 2025).

Active Ingredient	Sensitivity of Ragweed 1	Application Time
flumioxazin	7	Pre (just fruit), Post
glyphosate	9	Post
glyphosate + flazasulfuron	9	Post
MCPA	7	Post
flazasulfuron	8	Post
pelargonic acid	7	Post
pyraflufen-ethyl (plum, apple, cherry, grape)	7	Post

¹ Sensitivity of ragweed to the herbicide (6 = less effect 75–89%, 7 = good effect 90–94%, 8 = very good effect 95–98%, 9 = excellent effect 99–100%).

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2.5.1. Stubble Treatment

Particular attention should be paid to the stubble of autumn-sown crops (oilseed rape and winter cereals) as ragweed can create large populations in these habitats. After harvesting these crops, the ragweed can achieve a competitive advantage due to the lack of crops. To avoid the expansion of the soil weed seed bank and reduce weed infestation in the coming years, we must also protect against weeds on the stubble. It is worth mentioning that, after harvesting, a large area will be available for ragweed infestation; in Hungary alone, this includes about two million hectares. Professional stubble treatments are necessary to avoid the flowering and pollen emissions of ragweed. This can be done either mechanically (with a disc), chemically (generally with the application of non-selective glyphosate), or using a combination of the two methods. Stubble stripping must be done directly after harvesting [4]; this will promote seed germination by breaking seed dormancy, and later, a glyphosate treatment application is advised. In addition to glyphosate, flumioxazine and MCPA are also available for stubble treatments. In addition to their effectiveness against ragweed, their costs per hectare are also favorable [4]. However, the continuous use of herbicides also leads to resistance development, which poses a significant challenge to long-term weed control [93].

2.5.2. Herbicide Resistance

Herbicide resistance in weeds is now a real threat to crop production throughout the world, particularly in North America, Australia, China, and Brazil, and is increasing in Europe. The increasing occurrence of herbicide-resistant weed biotypes is a challenge for weed scientists [94]. Precise dosage and timing of applications is essential for effective weed control. In modern crop production, it is essential to integrate available weed management strategies to prevent the development of herbicide-resistant biotypes. Monoculture and herbicide use without crop rotation are conducive to the spread of evolved resistant biotypes. Resistance arises via target site resistance (TSR), which is the modification of herbicide target proteins, or by non-target site resistance (NTSR), which includes alterations in absorption, metabolism, transport, or sequestration pathways [95]. The first resistant ragweed biotype was found in maize in Canada (Ontario) in 1976. This first resistance event in ragweed was to atrazine, which had been used for many years in maize monocultures [96]. Atrazine resistance is inherited maternally, i.e., it is spread with the seed. Resistance is the result of an A790G point mutation in the psbA chloroplast gene, which encodes a serine to glycine substitution (S264G) in the D1 protein [91,92,93,94,95,96,97,98,99]. This single nucleotide substitution alters herbicide binding while preserving photosynthetic function. In the resistant biotypes, both resistant and sensitive alleles of the psbA gene can coexist in different copy numbers, i.e., the two types of chloroplast genome are present in a heteroplasmic state in these individuals [98]. A practical bi-PASA method has been developed to identify triazine-resistant Ambrosia plants. The major advantage of this method is that only one PCR reaction is required to detect both mutant and wild-type alleles. The basic idea behind this technology is that by using two external and two internal primers in the same reaction, two different sized products can be obtained, one specific for the mutant and the other for the wild type [100].

In Hungary, the atrazine-resistant ragweed biotype was first detected in 1992 and became widespread in the country nine years later [99]. In addition to triazines, ragweed biotypes resistant to linuron, another PSII inhibitor, have also been reported [101]. Resistant biotypes were first identified where linuron was used as a postemergence treatment for ragweed control. The efficacy of linuron gradually decreased and eventually ceased due to continuous use. Both triazine derivatives and linuron block the function of the D1 protein, thereby inhibiting the process of photosynthesis [70,102].

Recently, Kutasy et al. [103] investigated the ragweed photosystem II (PSII), acetohydroxyacid synthase (AHAS—alternative name for acetolactate synthase (ALS)), 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) and protoporphyrinogen oxidase (PPO) genes using a targeted amplicon sequencing approach. Mutations conferring resistance to linuron (PSII inhibitor) and imazetapyr (ALS inhibitor) were identified. It is concluded that amplicon sequencing based on high-throughput technologies is capable of detecting a diverse set of gene variants present in a large number of plant samples in a single reaction. Therefore, amplicon sequencing could effectively aid weed management by accurately detecting target site resistance in given populations.

Table 7 summarizes the herbicidal active ingredients to which resistance has been reported in A. artemisiifolia. The data presented here have been extracted from https://www.weedscience.org/Home.aspx (accessed on 17 July 2025). The source database lists several cases of herbicide resistance in which, in addition to ALS inhibitors, glyphosate and/or PPO resistance was also detected in the resistant plants. For PPO inhibitors, resistance is conferred by a single dominant gene mutation (R98L) in the PPX2 gene [104]. Interestingly, resistance to PPO inhibitors was only reported in cases of multiple herbicide resistance in Ambrosia. By sequencing the ALS gene of French ragweed populations, Loubet et al. [105] identified three and two codons, respectively, with a total of nine amino acid substitutions conferring resistance to imazamox and tribenuron herbicides. These results demonstrate that multiple, independent resistance evolutions confer resistance to ALS inhibitors in samples collected from ragweed populations throughout France. Glyphosate targets 5-enolpyruvyl-shikimate-3-phosphate synthase (EPSPS). In many weeds, resistance arises from amino acid substitutions at the active site (e.g., Pro106). For glyphosate resistance in Mississippi populations, Ref. [106] found increased herbicide translocation without target-site mutations or reduced absorption. Similarly, in an Ontario A. artemisiifolia population, no mutations at positions 102 or 106, which are frequently found in glyphosate resistant plants, were identified [107]. Instead, resistance appeared not to involve altered absorption, translocation, or metabolism, suggesting that alternative mechanisms, such as gene amplification or vacuolar sequestration, may be occurring.

Délye et al. [108] demonstrated the enormous power of high-throughput sequencing based on amplicon sequencing in the screening of ragweed populations resistant to ALS inhibitors. In this study, three regions of the ALS gene of 9600 A. artemisiifolia plants were sequenced with only two Illumina runs. To achieve the same results using Sanger sequencing would have required tens of thousands of reactions. Based on the above, it can be concluded that high-throughput sequencing has the potential to effectively monitor target site resistance in ragweed.

In addition to TSR, the genetic background of non-target site resistance (NTSR) in Ambrosia populations has been investigated by Loubet et al. [104,109]. NTSR is thought to be the main type of resistance to ALS inhibitors in ragweed, accounting for more than 70% of the cases studied. However, a variety of different resistance mechanisms were found to have evolved for NTSR in different populations. NTSR in A. artemisiifolia is polygenic and involves detoxification pathways of Cytochrome P450 monooxygenases (CYP71, CYP72, CYP94 families), which oxidize herbicides; ABC transporters, which actively pump herbicides or metabolites into vacuoles; Glycosyl/glucuronyl transferases, which conjugate herbicides to sugars; and Oxidoreductases, which contribute to metabolic detoxification [105]. NTSR enzymes and transporters collectively mitigate herbicide impact by reducing intracellular concentration and enhancing metabolic clearance. The complexity and diversity of the NTSR mechanisms studied suggest a non-redundant, population-specific evolution of NTSR to ALS inhibitors in Ambrosia. This suggests a rapid adaptation of ragweed to selective pressure. Therefore, local resistance management is as important, as it reduces gene flow from ragweed populations where resistance is already present. It should also be noted that the ineffectiveness of herbicides is not always due to genetic reasons, but may also be due to technical errors, such as inappropriate timing of spraying, overdeveloped ragweed plants, etc. [92]. Most of the resistant ragweed biotypes were found in North America (USA, Canada) in soybean, corn, carrot, and sunflower. In the EU, resistant ragweed is reported in Serbia, Ukraine, and France.

Table 7. Active ingredients of herbicides against which resistance in A. artemisiifolia has already been reported (source: www.weedscience.org).

Site of Action	Active Ingredient
Auxin mimics (HRAC Group 4) [110]	clopyralid
ALS inhibitors (HRAC Group 2) [104,111]	amidosulfuron
	chlorimuron-ethyl
	cloransulam-methyl
	diclosulam
	flazasulfuron
	flumetsulam
	foramsulfuron
	halosulfuron-methyl
	imazamethabenz-methyl
	imazamox
	imazaquin imazapyr imazethapyr iodosulfuron-methyl-Na metsufuron-methyl nicosulfuron
	primisulfuron-methyl prosulfuron pyriothiobac-sodium thiencarbazone-methyl tribenuron-methyl trifloxysulfuron-Na
PPO inhibitors (HRAC Group 14) [104]	acifluorfen carfentrazone-ethyl flumiclorac-pentyl flumioxan fomesafen lactofen oxyfluorfen pyraflufen-ethyl sulfentrazone
PSII inhibitors (HRAC Group 5) [104]	atrazine cyanazine linuron metribuzin simazine
EPSPS inhibitor (HRAC Group 9) [104]	glyphosate

HRAC—Herbicide Resistance Action Committee; ALS—acetolactate synthase; PSII—Photosystem II; EPSPS—5-enolpyruvylshikimate-3-phosphate synthase; PPO—Protoporphyrinogen oxidase.

Table 7. Active ingredients of herbicides against which resistance in A. artemisiifolia has already been reported (source: www.weedscience.org).

Site of Action	Active Ingredient
Auxin mimics (HRAC Group 4) [110]	clopyralid
ALS inhibitors (HRAC Group 2) [104,111]	amidosulfuron
	chlorimuron-ethyl
	cloransulam-methyl
	diclosulam
	flazasulfuron
	flumetsulam
	foramsulfuron
	halosulfuron-methyl
	imazamethabenz-methyl
	imazamox
	imazaquin imazapyr imazethapyr iodosulfuron-methyl-Na metsufuron-methyl nicosulfuron
	primisulfuron-methyl prosulfuron pyriothiobac-sodium thiencarbazone-methyl tribenuron-methyl trifloxysulfuron-Na
PPO inhibitors (HRAC Group 14) [104]	acifluorfen carfentrazone-ethyl flumiclorac-pentyl flumioxan fomesafen lactofen oxyfluorfen pyraflufen-ethyl sulfentrazone
PSII inhibitors (HRAC Group 5) [104]	atrazine cyanazine linuron metribuzin simazine
EPSPS inhibitor (HRAC Group 9) [104]	glyphosate

HRAC—Herbicide Resistance Action Committee; ALS—acetolactate synthase; PSII—Photosystem II; EPSPS—5-enolpyruvylshikimate-3-phosphate synthase; PPO—Protoporphyrinogen oxidase.

3. Ragweed Control on Non-Cultivated Areas

While control in agricultural fields is essential, the management of ragweed in non-cultivated areas presents unique challenges that require separate attention and modes of solution. Non-cultivated areas include ruderals, surrounding industrial parks, investments and constructions, inhabited areas, linear constructions, and natural and seminatural plant communities. In these places, both chemical and non-chemical methods against ragweed can be applied, depending on the habitats.

3.1. Ruderals

Non-selective herbicides can be used along linear constructions, such as railroad tracks. Herbicides for the selective control of broadleaf weeds should be applied when the preservation of the lawn cover is intended. The 2,4-D, glyphosate, dicamba, metsulfuron-methyl, flumioxazin, flazasulfuron, and MCPA can be used in ruderals. Hormone-type herbicides are preferred on ruderals because their major weeds generally belong to monocots, which promote natural succession processes [84]. The ragweed’s phenological phase is critical for successful weed control on ruderals. The mass emergence of ragweed may occur if the treatments are completed too early in June. If treatments are applied too late due to the large vegetative biomass of ragweed and the large foliage area, the efficacy will also not be sufficient (Figure 7) [4]. In general, mowing can be used to ensure that the area remains ragweed-free. In this case, a second mowing is also necessary in the second half of August to prevent regrowth and flowering. To minimalize reshooting, the weeds should be cut as close to the ground surface as possible when mowing. The number and timing of mowings are considered essential factors in ragweed infestation. Mowing too early (e.g., in May) delays pollen formation by a few days but increases the green mass and the number of male flowers. The best way to reduce seed and pollen production is by mowing immediately before pollen spreading, after the appearance of the male flowers [15,16,112]. There is an urgent need to develop new control methods against ragweed in non-cultivated areas like natural and seminatural habitats, such as planted lawn areas, roadsides, and ditch banks. Only the ragweed should be the target species in these areas, while other species should be protected [113].

3.2. Industrial Parks, Construction Sites

Ragweed can appear in large numbers at construction sites involving soil disturbance. It can be eradicated thermally with the help of a flamethrower; however, this method is not cost-effective. In terms of its results, similar to mowing, ragweed can grow again, so it does not cause its complete destruction. This method is more expensive and raises safety issues [11]. Weed control technologies do not typically deal with weed control technology at the investment site. In most cases, these areas are cleared of ragweed by mowing, and a one-time chemical treatment can keep these areas free from ragweed. Spraying units mounted on quads can provide a good solution that can be used to effectively control weeds in these areas [4].

3.3. Populated Areas

In smaller areas, like in populated habitats, ragweed control can be achieved by hand weeding, hoeing, or soil covering. When we apply mulch, the thickness of the mulch layer should be at least 6 cm. Special infrared or flaming devices can be used in the public areas, parks, decorative coverings, etc. Ragweed is very sensitive to high temperatures until it reaches a shoot length of 10 to 15 cm. Due to the heating, its cells are damaged and will dry out after 1–2 days. In inhabited areas, chemical control of ragweed is possible only with herbicides (e.g., glyphosate) that are practically non-toxic to humans. Mowing there may also be a good solution for ragweed control [4].

3.4. Along Linear Constructions

Non-selective herbicides must be applied along constructions where weeds are undesirable for safety reasons; otherwise, long-term herbicides, such as metsulfuron flazasulfuron, are recommended to ensure that the area is weed-free. In areas where maintaining the monocot cover is important, selective herbicides against dicot weeds should be applied [76]. Generally, mowing is used twice during the ragweed vegetation period at roadsides and ditch banks where the natural flora should be kept.

3.5. Natural and Semi-Natural Habitats

The most effective method is prevention, so we must prevent the introduction of ragweed into new habitats. Ragweed spread is closely linked to human activity, so preventing soil disturbance and driving in machines can avoid introducing ragweed seeds or promoting their germination in protected areas. In recently abandoned cultivated areas, the establishment of ragweed can be prevented by sowing native grass species and mowing at least twice a year. Excavation should also be avoided in abandoned places as this enhances the germination of ragweed. Mowing twice a year is recommended in areas infested with ragweed and other weeds because this helps the growth of perennial monocot species and suppresses the less desirable ones. Using herbicides in semi-natural associations and fields rich in endangered species is not recommended [4]. Beyond traditional methods, technological advancements offer novel opportunities for targeted and efficient weed management, as discussed in the following section.

4. New Tools and Methods of Weed Survey and Control

Precision agriculture relies on technologies that combine sensors, information systems, and management to optimize crop productivity and reduce environmental impact [114]. GPS technologies are essential for precision technology because they provide geographic information for GIS (geospatial information). With the help of satellites, it is possible to monitor large areas in just a few minutes. With the data provided by the technology, a more accurate picture of the weed conditions in the given area can be obtained, and a much better weed control plan can be created [115]. Depending on the weed species, different sensors, like RGB/VIS, multispectral, and hyperspectral sensors, can be used [116]. Unmanned aerial vehicles (UAVs) are considered one of the most successful technologies in precision agriculture (Figure 8) [117].

UAVs offer great potential in applying site-specific weed management (SSWM). SSWM can be characterized by high efficacy and environmentally friendly solutions [118]. In the past 15 years, significant progress has been made in Hungary in precision agriculture. Today, routinely applicable precision methods are available for practice in various weed control areas [119]. Currently, precision farming tools are used by farmers who have a larger farm size; they are younger, full-time farmers who have completed higher education and are open to training and innovation. The proportion of Hungarian farmers using precision technology is 23%, close to the EU-27 average (25%). Digital infrastructure provides a sound basis for further spreading [120]. The application of precision technology is hindered because farmers generally do not like to spend money on long-term profitable investments [121], using technologies such as the sensor-controlled inter-row cultivator and strip sprayer. The optics mounted on the cultivator monitor the rows. The computer system processes the images transmitted by the optical system, identifies the rows of the cultivated plant, and determines their position in relation to the position of the cultivator. The inter-row cultivator operates on the hydraulic system of the power machine; its lateral movement relative to the tractor is corrected by the hydraulic cylinders. The system works with an accuracy of 2 cm. With this technology, the amount of herbicide applied to the area can be reduced, and the soil-improving effect of cultivation is also effective. This technology is recommended under 25–30% weediness [11].

An accurate weed survey must always precede planned treatments during precision weed control. Herbicides are applied based on the weed map prepared with the weed survey [122]. The camera application allows weed identification for the UAV [123]. The weed identification determination accuracy depends on the analysis software’s accuracy [122]. Information technology and computers with increasing performance will provide a suitable background for the developing weed control technology in the future. These systems will be able to make decisions about weed control technology [124].

The integration of known and developing technologies will significantly improve precision weed control. Using image analysis and various machine learning technologies, they will be able to provide a reliable overview of the level and type of weed infestation. With specific algorithms, autonomous weeding robots will be able to be programmed to remove weeds [125]. In the future, autonomous weeding robots (Figure 9) will provide an excellent opportunity for herbicide-free weed control. These weeding robots recognize the weeds with the help of a camera and then move over the rows to destroy them. The latest models are equipped with a solar panel, thus providing the energy needed for movement, sensing, and weeding [126]. Weed surveys can be done with drones programmed in the field. Investment in drones, including software and other additional systems, will only pay off in the long term [127]. In addition to the current research results, further research on weed population dynamics and competitive effects are necessary for the practical utilization of these new technologies. The research findings will allow for the implementation of new technologies and the removal of only harmful weeds [115,128]. Ngom and Gosselin [129] used three different optical sensors to determine ragweed in urban areas. Ragweed was identified based on its radiometric spectrum. The spectrum emitted by the ragweed was different during the recordings made at different times points, which probably changed due to the stress effect caused by a drought in the study area in June. Large densities of ragweed vegetation are easier to detect, whereas individuals in low densities require higher-resolution optical sensors.

Adhinata et al. [130] used a multispectral camera to determine ragweed cover on wheat stubbles. From the recordings, ragweed can be easily separated from soil and stubble residues, but separating it from other weed species is difficult. Later, hyperspectral recordings were also made, and with this data, ragweed could be separated from other weed species. Plaščak et al. [131] used a helicopter and a drone, then took photos of the investigated area in the visible light and infrared spectrum with a near infrared (NIR) + Green + Blue (NGB) camera. Using the normalized green-red difference index (NGRDVI) index on the images taken by the camera (Figure 10), it was possible to determine which structures were cultivated and which were not. With the help of remote sensing, the distribution area of A. artemisiifolia can be precisely determined. Because of its relevance to health and agricultural importance, this detection method will likely be widely used to record ragweed infestation. Technologies with multiple chemical tanks are available where the sprayer, as required, can immediately change the dissolved active ingredient ratio of different substances filled with different chemicals. According to the weed detected by the camera at the given location, herbicides can effectively be applied in a weed-specific manner.

5. Official Measures and Pollen Monitoring in HU

In addition to practical control techniques, institutional and regulatory frameworks—such as pollen monitoring and official control measures—play a pivotal role in coordinated ragweed suppression.

These systems will be able to make decisions about weed control technology [1]. The official action against A. artemisiifolia L. became necessary due to its serious risk to human health and serious damage caused to agriculture [132]. In order to ensure the basic right to health and a healthy environment, the main goal is to prevent the spreading and generative reproduction of ragweed. Its prominent role is primarily justified by public health considerations and allergen production [4]. Pollen concentration has been monitored in Hungary since 1992 [13]. Many countries in the EU operate pollen monitoring system. In all the countries, there was an increase in ragweed pollen density. The pollen season starts at July and ends in October. The highest pollen concentrations are measured in August and September [133]. In HU, the National Institute of Environmental Health (OKI) determines the pollen concentration in the air with the help of 19 pollen monitoring stations (one station for each county; at present, 19 pollen traps are in use in HU [134]. The pollen is collected with a Hirst-type sampler, and the inhaled air is hit against a sticky sheet, on which the pollen sticks. During the analysis of the number of pollens collected by the sticky sheets, pictures of the collected pollen are taken using a camera mounted on a microscope, which can be analyzed immediately or even later using special software. After 2011, the time and length of the pollen release season, as well as the distribution by area, are also available during the pollen season. OKI, in cooperation with the European Health Information System (ENHIS), created a coordinated European-level database where the four most important pollen indicator plants can be queried. Out of the pollen indicators, the fourth is the ragweed, which causes significant human health problems throughout Europe, and due to its expected spread, its importance and pollen production will increase in the next 50 years. According to studies by the Hungarian Aerobiological Network, the average annual total pollen count of ragweed in air samples of five Hungarian cities shows a slightly increasing trend (p < 0.05 *) in the period 1992–2022 [135].

There is a pollen alarm system (PPRR) in HU, whose aim is to determine the weekly ragweed pollen concentration and its spreading with a higher degree of accuracy. Daily maps of the PPRR and the data collected every two hours by the OKI and the aerobiological net of the NTSZ provide good information for the human population and patients [136]. In spite of decades of community-scale protection against ragweed and a lot of effort and financial expenditure, the spreading of ragweed did not stop [137]. Today, it is considered a dominant weed species in HU in 5% of the agricultural areas (if there was no protection against it). The International Ragweed Conference was held for the first time in Hungary (Budapest) (10–13 September 2008). This event was also held in Budapest in the autumn of 2022.

The ragweed map of the country is prepared by the Hungarian Institute of Geology and Geophysics and the Institute of Land Surveying and Remote Sensing based on the previous year’s infected areas, aerial photographs, field surveys, and other data. This map is available at the district offices as well as electronically on the websites of the Hungarian Institute of Geology and Geophysics and the Ministry of Agriculture [13].

According to Decree 43/2010 (IV. 23), land users and producers are obliged to protect against ragweed. Furthermore, 221/2008. (VIII. 30.) government decree contains detailed rules for the implementation of public interest protection against ragweed, as well as the determination and claim of the costs of state and public interest protection. The decree states that public interest protection must be carried out purposefully, cost-effectively, efficiently, and with the least possible environmental damage.

In the outer areas, the Plant and Soil Protection Directorate of the capital and County Government Offices oversees the protection of the public interest; in the inner areas, the clerk of the local government orders the protection of the public interest. The ordering of a public interest defense establishes the basis for imposing a plant protection fine since the land user in this case did not fulfill their obligations as a land user. The fine is imposed by the Plant and Soil Protection Directorate of the Government Office. In an order, the competent government office obliges the land user to pay the following items as the cost of the public interest defense: the contractor’s fee incurred (if the contractor carried out the public interest defense) or the cost of the contractor’s departure for no reason (if the client failed to notify the authority that he had carried out the defense and the contractor went to the site). The plant protection fine is based on the size, the habitat, and the severity of infestation. The amount of the fine ranges from HUF 15,000 to HUF 5,000,000.

The land user is obliged to prevent the formation of flower buds of ragweed and thereafter to maintain this condition continuously until the end of the vegetation period.

Protection against ragweed must be ordered if the land user does not comply with the obligation to protect against it detailed in Section 17 (4). Protection against ragweed in the public interest can be ordered if the surface coverage by weeds exceeds 30%. The land user cannot claim compensation for the damage caused to the affected culture during the public interest protection against ragweed.

Patkó et al. [138] investigated the efficacy of government ragweed control in Komarom-Esztergom county (in Hungary). He made the following conclusions: a legal consequence should be defined that is not limited to the payment of a fine but has a long-term effect on the user of the affected area (e.g., SAPS withdrawal). On the other hand, voluntary law-abiding behavior should also be evaluated by the system. Simplifying and speeding up the procedure and condensing it into one official procedure could reduce the length of the procedure, thereby also reducing the pollen load, since the owners and land users usually voluntarily exempt their area after being notified of the initiation of the procedure. In order to carry out targeted inspections by car, it would be advisable to extend the fastest and most effective reconnaissance method, aerial reconnaissance (remote sensing with a hyperspectral camera), to all counties of the country. In addition to producers and land users, it would also be essential to inform the civilian population. Suitable channels include national, regional, and local TV channels and radio stations. Furthermore, it is critical to begin education and environmental awareness education in elementary schools by including ragweed knowledge in mandatory course educational material [4].

6. Discussion

In this review, we sought to answer the question of how integrated weed management approaches can be optimized in different habitats and what role new technologies can play in this. Successful control of ragweed is a complex process and requires the professional application of integrated weed control elements. This question can only be adequately answered if the combination of methods is tailored to the specific needs of the habitat (e.g., field, urban, or natural), and it is not possible to define an integrated weed control technology that is universally valid for all habitats [29,46].

6.1. Comparative Effectiveness of Control Methods

6.1.1. Chemical Methods

Chemical management is the most widely used, the cheapest, and had the highest territorial performance. With a properly selected herbicide, over 95% efficacy can be achieved against ragweed [68]. The chemical management of ragweed can harm the environment and has a harmful effect on human health, especially when it is overdosed. With herbicides, we put a strong selective pressure on the weed flora of the area and promote the proliferation of difficult to eradicate weeds. One-sided herbicide use leads to the development of resistant weeds, which makes it difficult to manage weeds in the crops. It has a relatively fast effect, and preemergence application is available to destroy the weeds during germination and terminate the possibility of early competition [68,90]. Since resistance to multiple herbicide classes—including PSII, ALS, PPO, and EPSPS inhibitors—has already been documented, it is of utmost importance to integrate resistance monitoring into national weed management strategies. Moreover, the molecular diversity and adaptive capability of ragweed ensure rapid resistance under constant selection pressure. This increases awareness that there are both cost-effectiveness and ecological reasons to avoid overusing or misapplying herbicides. Therefore, molecular diagnostics and high-throughput sequencing should become standard practice in order to effectively control ragweed in agroecological systems.

6.1.2. Biological Control

Biological ragweed management is only possible with O. communa. Only this insect can effectively reduce the population of A. artemisiifolia; the effectiveness is about 80%. The most important question of biological control was the extent to which biological control by Ophraella communa can be applied under field conditions, taking into account the use of insecticides and successful overwintering. This insect can effectively reduce the assimilation surface, pollen, and seed production of A. artemisiifolia [33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50]. It can be concluded that their application in ruderal and uncultivated areas is promising, but their applicability in fields is limited, as in the latter case, insecticides and climatic effects hinder stable establishment, and multigenerational drawings are not guaranteed in agricultural environments [50].

6.1.3. Mechanical and Thermal Methods

The integration of the recent findings of the revised literature regarding ragweed control technologies reveals that effectiveness requires an integrative approach of mechanical, chemical, biological, and digital tools, adapted to specific habitats.

Agrotechnical control is one of the most important ways to reduce the soil seed bank and manage herbicide resistance. The percentage-based effect on this method is not significant, but it is very important in integrated weed management technology. On the stubbles and in sowing change (in monocotyledonous crops, there are many herbicide possibilities to break resistance), we can easily reduce the number of A. artemisiifolia.

Mechanical weed management also had good efficiency, over 90% against seed-bearing weeds. But for perennial weeds which can reproduce from vegetative organs, the shallow mechanical treatment promotes proliferation [8,10]. Among non-chemical technologies, mechanical methods are the most wide-ranging. The advantage of mechanical management is that, in some cases, nutrient recycling can occur in parallel. It has a good effect against ragweed and reduces herbicide load; however it is more expensive, has a lower territorial performance, and can harm the crops as well. With sensor or AI-driven precision, technology has a very good effect, up to 99%. Thermal ragweed management is also very expensive and does not have a good effect because of the fast regeneration, and it is very expensive [10,12].

6.1.4. Precision Technologies

The new perspective could be the use of sensors and AI-driven devices that can operate autonomously in a location-specific way and use new technologies to eliminate the weeds (for example, using high-energy lasers to burn out the meristem tip of weeds at an early stage of weed development). It is essential to apply drones to provide accurate weed surveys to lay the foundations for efficient and environmentally friendly weed management [114,115,116].

6.2. Trade-Offs and Limitations of Different Weed Control Technologies

Regarding chemical vs. non-chemical control, it can be stated that chemical control is very fast, and the use of chemicals does not require a high level of technology or professional knowledge. The advantage of mechanical management is that, in some cases, nutrient recycling can occur in parallel. The application of biological agents in ruderal and uncultivated areas is promising, but their applicability in the field is limited, as in the latter case, insecticides and climatic effects hinder stable establishment, and multigenerational drawings are not guaranteed in agricultural environments.

Thermal management, on the other hand, has a good efficiency, of about 100 percent, but because the roots are not damaged, the ragweed can regenerate quickly. New technologies, such as AI and sensor-driven robots, offer the opportunity to destroy weeds before competition takes effect. The limitation of these technologies is the large amount of investment. Regardless, adopting these technologies is inevitable because they allow more sustainable, efficient, and environmentally friendly weed control practices that are essential elements of future farming [116].

Effective control of ragweed is challenged by its constantly evolving resistance and its high adaptability and regeneration capacity. The effectiveness of control methods is further hampered by the impact of climate change, which has altered normal germination and flowering times. Ragweed can germinate in large numbers in autumn crops even in warm, wet autumns, and it remains in the field for long periods due to late frosts. We need to study how climate change alters the behavior of ragweed and monitor resistance. To manage resistance, we can use herbicides with differing sites of action and use alternative methods with a higher proportion; we have to apply the integrated weed management strategy (IWM) [4,28,110,112].

Furthermore, decision support systems are inevitable. It is very important to educate growers about integrated weed management of ragweed and how to manage emerging resistance. Along with individual weed management, a coordinated strategy at the regional, national, and European levels is key to managing the ragweed problem.

6.3. Future Research

Future research is needed on the applicability and field effectiveness of Ophraella communa. From the current state of the art, it can be concluded that their application in ruderal and uncultivated areas is promising, but their efficiency in the field is limited, as in the latter case insecticides and climatic effects hinder stable establishment, and multigenerational drawings are not guaranteed in agricultural environments.

Sustainability is a key factor when the introduction or widened use of a new technology is considered; therefore, long-term ecological impact should be carefully taken into account.

Integrated weed control technology must be continuously improved to ensure effective control of ragweed under rapidly changing climatic conditions. A truly effective control of A. artemisiifolia will require not only innovation but also an approach that balances efficiency, sustainability, and environmental responsibility [69,110,112,139,140,141].

According to the results of this review, precision technologies (drones and sensor-based weed detection) allow for targeted, environmentally sound interventions, so that it is perhaps in our time that truly specific, multi-scale control can be effectively implemented for the first time. This optimization is based on prevention, monitoring, and the flexible use of varied control techniques [8]. Individual control methods may provide success, but they are often ineffective when applied in the same manner among diverse environments. Therefore, management strategies should be tailored to the biological characteristics of ragweed, the crop type, local climatic conditions, and land use. Only by coordinating these factors can lasting reductions be achieved. Further research should focus on evaluating combinations of methods under farming conditions, monitoring the chances of resistance, and assessing the ecological safety of biological agents.

In order to manage ragweed sustainably, it is necessary to change the current practice of ragweed control from herbicide-based approaches towards a more integrative weed control system based on detailed ecological knowledge and integration of technological advancements. Although ragweed’s distribution and phenology are expected to change due to climate change, this will present both new challenges and opportunities for adaptive ragweed management. As the most promising current approach, an integrated weed management that considers environmental protection issues provides an effective approach to ragweed management. Technological advancements provide novel possibilities, with the most significant breakthrough anticipated from the application of AI in agriculture. Despite all efforts, ragweed will persist and cause harm; however, its population and detrimental impact can be reduced by the professional, integrated application of effective control methods.

International cooperation is needed in order to reduce its damage, and the process must involve not only plant protection experts, herbologists, and farmers, but also conservationists, the population, civil society organizations, and decision-making organizations. Although we already know a lot about the biology of ragweed, which is summarized in the first part of our ragweed review (1), and the effectiveness of its different control methods based on its biological characteristics (see this paper), ragweed still remains an unresolved problem; therefore, research that examines both its biology and the technology to control it must continue.