Search Results (18)

Determining the effectiveness of fungicide programs based on cultivar resistance to pathogens, especially late leaf spot (caused by Nothopassalora personata (Berk. & M.A. Curtis) [U. Braun, C. Nakash., Videira & Crous]) is important in establishing recommendations to peanut (Arachis hypogaea L.) farmers. Research was conducted in North Carolina during 2021 and 2022 at three locations to compare the incidence of late leaf spot (e.g., visual estimates of percent of peanut leaflets with lesions), percentage of the peanut canopy defoliated caused by this disease, and yield of the peanut cultivars Bailey II, Emery, and Sullivan when exposed to five fungicide regimens including a non-treated control. Peanut yield was not affected by the interaction of cultivar × fungicide regimens. While differences in leaf spot incidence and canopy defoliation were noted for cultivars, these differences did not translate into differences in peanut yield. All fungicides regimens protected peanut yield from leaf spot disease regardless of the number of sprays during the cropping cycle (e.g., three, four, or five sprays). Peanut yield in the absence of fungicides was 4410 kg/ha compared with a range of 5000 to 5390 kg/ha when fungicides were applied. Peanut yield was greater when fungicides were applied four or five times compared with only three sprays or non-treated peanut. The regimen with five consecutive sprays of chlorothalonil alone for the first and final spray in the regimen and when this fungicide was applied with tebuconazole for the second, third, and fourth sprays was as effective as fungicide regimens including combinations of pydiflumetofen plus azoxystrobin plus benzovindiflupyr, mefentrifluconazole plus pyraclostrobin plus fluxapyroxad, bixafen plus flutriafol, and prothioconazole plus tebuconazole. Full article

The sterol demethylation inhibitors (DMIs) are among the most widely used fungicides for controlling black Sigatoka (Mycosphaerella fijiensis) and yellow Sigatoka (Mycosphaerella musicola) in banana plantations in Brazil. Black Sigatoka is considered more important due to causing yield losses of up to 100% in commercial banana crops under predisposing conditions. In contrast, yellow Sigatoka is important due to its widespread occurrence in the country. This study aimed to determine the current sensitivity levels of Mf and Mm populations to DMI fungicides belonging to the chemical group of triazoles. Populations of both species were sampled from commercial banana plantations in Registro, Vale do Ribeira, São Paulo (SP), Ilha Solteira, Northwestern SP, and Janaúba, Northern Minas Gerais, and were further characterized phenotypically. Additionally, allelic variation in the CYP51 gene was analyzed in populations of these pathogens to identify and characterize major mutations and/or mechanisms potentially associated with resistance. Sensitivity to the triazoles propiconazole and tebuconazole was determined by calculating the 50% inhibitory concentration of mycelial growth (EC₅₀) based on dose–response curves ranging from 0 to 5 µg mL⁻¹. Variation in sensitivity to fungicides was evident with all nine Mf isolates showing moderate resistance levels to both propiconazole or tebuconazole, while 11 out of 42 Mm strains tested showed low to moderate levels of resistance to these triazoles. Mutations leading to CYP51 substitutions Y136F, Y461N/H, and Y463D in Mm and Y461D, G462D, and Y463D in Mf were associated with low or moderate levels of resistance to the triazoles. Interestingly, Y461H have not been reported before in Mm or Mf populations, and this alteration was found in combination with V106D and A446S. More complex CYP51 variants and CYP51 promoter inserts associated with upregulation of the target protein were not detected and can explain the absence of highly DMI-resistant strains in Brazil. Disease management programs that minimize reliance on fungicide sprays containing triazoles will be needed to slow down the further evolution and spread of novel CYP51 variants in Mf and Mm populations in Brazil. Full article

Rhizoctonia large patch (Rhizoctonia solani AG2-2 LP) significantly reduces turfgrass quality, aesthetics, and playability. Synthetic fungicides are commonly used for managing this disease, but they present high costs, potential for fungicide resistance, and environmental concerns. We conducted in vitro assays to test the effectiveness of three biofungicides, seven synthetic fungicides, and ten combinations against R. solani. We then assessed seven spray programs that included Bacillus subtilis QST713 and propiconazole, either alone or tank-mixed, on zoysiagrass ‘El Toro’ in a growth chamber and in field trials. Biofungicide B. subtilis QST713 reduced pathogen growth by up to 100% in vitro. B. subtilis QST713 alone or combined with synthetic fungicides and/or in rotation was as effective as the standalone synthetic fungicide, reducing disease severity and AUDPC by 81 and 77% (growth chamber) and by 71 and 52% (field), respectively, while maintaining acceptable turfgrass quality. Additionally, we screened zoysiagrass genotypes and advanced breeding lines against three R. solani isolates in growth chamber studies. Five genotypes and two breeding lines demonstrated resistance to Rhizoctonia large patch across isolates, highlighting their potential for developing disease-resistant cultivars. Our findings suggest that integrating biofungicides, resistant cultivars with chemical controls offer sustainable and effective strategies for managing Rhizoctonia large patch Full article

Foliar fertilizing is very important to supply apple plants with calcium and micronutrients. The most cost-effective approach to this is the application of the fertilizers in tank mixtures with plant protection chemicals. Plasma-activated water (PAW) has great potential for the use in the agriculture. We used two type of PAWs, PAW1 (made using underwater electrical discharge in an aqueous KNO₃ solution and includes reactive nitrogen species and platinum nanoparticles) and PAW2 (made using a plasma torch with nitrogen gas makeup and contains reactive nitrogen species but not metals). We studied the impact of two PAW types on the contents of Ca, B, Mn, Fe, and Co in leaves and Ca, Mn, Fe, Zn, and Mo in fruits sprayed with tank mixtures containing the fertilizers. We also tested the efficiency of PAW in the control of apple scab when applied as tank mixtures with plant protection chemicals. The application of the PAWs significantly increased foliar Ca when the PAW was mixed with Ca-containing formulations (spraying PAW1 containing Ca increased leaf Ca by up to 21%, and PAW2 up by to 9% compared to Ca spraying without PAW). The largest fruit Ca increase was in the variant treated with PAW1 with a micronutrient spraying program (up to 143%). The PAW treatments enhanced the baseline mineral contents of the plants even when they were not sprayed with the nutrients. PAW1 mainly increased the nutrient contents of the apple fruits. PAWs have proven to be efficient for the control of apple scab, thereby reducing the demand for fungicides. The scab damage to the leaves and fruits was similar in plants treated with PAWs without fungicides (1.7–1.9% on the leaves and 1.6–1.8% on the fruits) compared to the conventional chemical scab control (0.9% leaves and 0.6% fruits) and was significantly lower than in the untreated control (9.3% on leaves and 11.9 on fruits). Full article

Mancozeb (MZ) is a broadly used fungicide for the control of plant diseases, including late blight in potatoes caused by the oomycete Phytophthora infestans (Mont.) De Bary. MZ has been banned for agricultural use by the European Union as of January 2022 due to its hazards to humans and the environment. In a search for replacement fungicides, twenty-seven registered anti-oomycete fungicidal preparations were evaluated for their ability to mitigate the threat of this disease. Fourteen fungicides provided good control (≥75%) of late blight in potted potato and tomato plants in growth chambers. However, in Tunnel Experiment 1, only three fungicides provided effective control of P. infestans in potatoes: Cyazofamid (Ranman, a QiI inhibitor), Mandipropamid (Revus, a CAA inhibitor), and Oxathiapiprolin + Benthiavalicarb (Zorvek Endavia, an OSBP inhibitor + CAA inhibitor). In Tunnel Experiment 2, these three fungicides were applied at the recommended doses at 7-, 9-, and 21-day intervals, respectively, totaling 6, 4, and 2 sprays during the season. At 39 days post-inoculation (dpi), control efficacy increased in the following order: Zorvec Endavia > Ranman > Revus > Mancozeb. Two sprays of Zorvec Endavia were significantly more effective in controlling the blight than six sprays of Ranman or four sprays of Revus. We, therefore, recommend using these three fungicides as replacements for mancozeb for the control of late blight in potatoes. A spray program that alternates between these three fungicides may be effective in controlling the disease and also in avoiding the build-up of resistance in P. infestans to mandipropamid and oxathiapiprolin. Full article

Grape powdery mildew caused by Erysiphe necator (Schw.) Burr. is a destructive disease in vineyards. Synthetic fungicides are the main tool to combat this disease. The search for new alternatives to reduce pesticide usage and tactical approaches for resistance management encouraged us to develop the novel strategy that we report here. We evaluated the efficacy of a new premixed hybrid fungicide containing the demethylation inhibitor (DMI) difenoconazole and essential tea tree oil (TTO), derived from the Melaleuca alternifolia plant, against grape powdery mildew in seven field trials and two large-scale demonstration trials conducted in two different regions in the world, including Chile and Israel. Foliar sprays of difenoconazole-TTO were applied as a preventive treatment in field trials at 40–80 up to 80–160 gr/ha active ingredient, and they were highly effective in controlling powdery mildew on the fruit clusters of both wine and table grapes in experimental and large-scale demonstration trials and provided up to 99% efficacy in disease incidence and severity compared with the untreated control. Difenoconazole-TTO was as or more effective than other DMI fungicides, including difenoconazole, a pre-mixed fungicide boscalid-pyraclostrobin, or treatments that included various fungicides applied in rotation or mixtures of fungicides. The results suggest that a combination of difenoconazole-TTO with a reduced synthetic chemical load can be included in powdery mildew control programs for grapevine as a strategic approach in fungicide resistance management in vineyards. Full article

Monilinia spp. is the main pathogen that affects stone fruit, causing significant production losses, especially in seasons with favorable climatic conditions for disease development. Currently, the standard practices for controlling this disease are by means of spray programs of synthetic fungicides. Fungicide applications using treatment schedules imply an increase in the number of applications; however, the applications are justified considering the real risk of Monilinia spp. infection. Consequently, fruit surface contains a higher number and concentration of residues, but not better control of the disease. From previous studies, the epidemiology of Monilinia spp. was deeply studied in one of the main stone fruit regions of Europe, the ‘Valle del Ebro’, and an epidemiological model was developed to describe the brown rot epidemic pattern in this area. After that, a warning system for fungicide applications in the field was elaborated that included the main factors to be considered as fruit susceptibility, the presence of inoculum in the field, and climatological factors (temperature, leaf wetness, rainfall, or their interaction). In the present study, we present data of the warning system validation during six seasons in 38 fields of peaches and nectarines of the ‘Valle del Ebro’. The results indicated that the incidence of disease caused by Monilinia spp., recorded in the field and postharvest, was similar in both plot evaluations and the calendar and warning systems. However, the disease level was higher in late varieties (3.2% and 9.3% of infected fruit recorded in the field and in postharvest, respectively) in comparison with earlier varieties (0.6% and 3.1% of infected fruit recorded in the field and in postharvest, respectively). In general, the strategy applied (the calendar or warning system) did not affect the disease level recorded. However, when fungicide treatments were applied following the warning system, the treatment reductions were higher than 50% in 96% of the trials in early varieties; meanwhile, in late varieties, this level of reduction was obtained in 77% of trials. Our data encourage the use of the proposed warning system as an effective strategy to control Monilinia spp. in peaches and nectarines, reducing the number of chemical treatments applied in the field with a high level of efficacy. Full article

The application of remote sensing techniques and prediction models for soybean rust (SBR) monitoring may result in different fungicide application timings, control efficacy, and spraying performance. This study aimed to evaluate the applicability of a prediction model as a threshold for disease control decision-making and to identify the effect of different application timings on SBR control as well as on the spraying technology. There were two experimental trials that were conducted in a 2 × 4 factorial scheme: 2 cultivars (susceptible and partially resistant to SBR); and four application timings (conventional chemical control at a calendarized system basis; based on the prediction model; at the appearance of the first visible symptoms; and control without fungicide application). Spray deposit and coverage at each application timing were evaluated in the lower and upper region of the soybean canopy through quantitative analysis of a tracer and water-sensitive papers. The prediction model was calculated based on leaf reflectance data that were collected by remote sensing. Application timings impacted the application technology as well as control efficacy. Calendarized system applications were conducted earlier, promoting different spray performances. Spraying at moments when the leaf area index was higher obtained poorer distribution. None of the treatments were capable of achieving high spray penetration into the canopy. The partially resistant cultivar was effective in holding disease progress during the crop season, whereas all treatments with chemical control resulted in less disease impact. The use of the prediction model was effective and promising to be integrated into disease management programs. Full article

Powdery mildew caused by the fungus Erysiphe necator is a major grape disease worldwide. It attacks foliage and berries and reduces yield and wine quality. Fungicides are mainly used for combating the disease. Fungicide resistance and the global requisite to reduce pesticide deployment encourage the use of environment-friendly alternatives for disease management. Our field experiments showed that the foliar application of the potassium phosphate fertilizer Top-KP+ (1-50-33 NPK) reduced disease incidence on leaves and clusters by 15–65% and severity by 75–90%, compared to untreated vines. Top-KP+ mixed with Nanovatz (containing the micronutrients boron (B) and zinc (Zn)) or with TruPhos Platinum (a mixture containing N, P₂O₅, K₂O, Zn, B, Mg, Fe, Mn, Cu, Mo, and CO) further reduced disease incidence by 30–90% and disease severity by 85–95%. These fertilizers were as effective as the fungicide tebuconazole. Tank mixtures of fertilizers and tebuconazole further enhanced control efficacy in the vineyards. The modes of action of fertilizers in disease control were elucidated via tests with grape seedlings, microscopy, and berry metabolomics. Fertilizers applied preventively to the foliage of grape seedlings inhibited powdery mildew development. Application onto existing mildew colonies plasmolyzed mycelia and conidia and arrested the development of the disease. Berries treated with fertilizers or with a fungicide showed a significant increase in anti-fungal and antioxidant metabolites. Twenty-two metabolites, including non-protein amino acids and carbohydrates, known for their anti-fungal and bioactive effects, were significantly upregulated in grapes treated with fertilizers as compared to grapes treated with a fungicide, suggesting possible indirect activity against the pathogen. Esters and organic acids that contribute to wine quality were also upregulated. We conclude that integrating macro and micronutrients in spray programs in commercial vineyards shall control powdery mildew, reduce fungicide deployment, delay the buildup of fungicide resistance, and may improve wine quality. Full article

Fusarium head blight (FHB) is an important disease of small grain cereals worldwide, resulting in reduced yield and quality as well as the contamination of harvested grains with mycotoxins. The key mycotoxin of concern is deoxynivalenol (DON), which has legislative and advisory limits in numerous countries. Cereal growers have a number of control options for FHB including rotation, cultivation, and varietal resistance; however, growers are still reliant on fungicides applied at flowering as part of an IPM program. Fungicides currently available to control FHB are largely restricted to triazole chemistry. This study conducted three field experiments to compare a new co-formulation of pydiflumetofen (a succinate dehydrogenase inhibitor (SDHI) with the tradename ADEPIDYN^™) and prothioconazole (a triazole) against current standard fungicides at various timings (flag leaf fully emerged, mid-head emergence, early flowering, and late flowering) for the control of FHB and DON. Overall, the co-formulation showed greater efficacy compared to either pydiflumetofen alone or current fungicide chemistry. This greater activity was demonstrated over a wide range of spray timings (flag leaf fully emerged to late flowering). The availability of an SDHI with good activity against FHB and the resulting DON contamination of harvested grain will give growers an additional tool within an IPM program that will provide a greater flexibility of spray application windows and reduce fungicide resistance selection pressure. Full article

Coffee is one of the most important cash crops and beverages in the world. Production of coffee is limited by many factors, which include insect pests and diseases, among others. One of the most devastating coffee diseases in many coffee-producing countries is Coffee Leaf Rust caused by the fungus Hemileia vastatrix. Kenya is a coffee-producing country and has conducted studies to understand and manage the disease. Management strategies for the disease include the development and use of fungicide spray programs, cultural control practices, breeding resistant coffee varieties, and biological control agents. This paper reviews the status of the disease and management options applied in Kenya. Full article

Grapevine powdery mildew is a principal fungal disease of grapevine worldwide. Even though it usually does not cause plant death directly, heavy infections can lead to extensive yield losses, and even low levels of the disease can negatively affect the quality of the wine. Therefore, intensive spraying programs are commonly applied to control the disease, which often leads to the emergence and spread of powdery mildew strains resistant to different fungicides. In this review, we describe major fungicide classes used for grapevine powdery mildew management and the most common single nucleotide mutations in target genes known to confer resistance to different classes of fungicides. We searched the current literature to review the development of novel molecular methods for quick detection and monitoring of resistance to commonly used single-site fungicides against Erysiphe necator. We analyze and compare the developed methods. From our investigation it became evident that this research topic has been strongly neglected and we hope that effective molecular methods will be developed also for resistance monitoring in biotroph pathogens. Full article

Among the fungal diseases that affect wheat in temperate growing areas, Septoria Leaf Blotch (SLB) and Fusarium head blight (FHB) result in yield and sanitary risk losses that could be minimized through appropriate fungicide applications. Furthermore, the request from policy makers and the food market to reduce the use of chemical pesticides in agriculture has driven research in the direction of performant defense strategies with a reduced spraying of pesticides. The aim of this study was to evaluate the effects of different fungicide programs on the control of SLB and FHB, as well as on the grain yield and deoxynivalenol (DON) contamination of common wheat. Field experiments were carried out in 2016 and 2017 in North Italy. Two seed treatments (conventional vs. systemic) and four combinations of foliar fungicide applications (untreated control, application at the end of stem elongation, at flowering, and a double treatment at stem elongation and flowering) have been compared, according to a full factorial design, under two agronomic conditions: plowing vs. minimum tillage. Foliar sprayings at the end of stem elongation were found to be more effective in controlling SLB, while a triazole application at flowering was found to be an essential practice to reduce the FHB and DON contents. The double foliar treatment led to significant benefits, albeit only in the production situations with the highest SLB severity (e.g., in the 2017 experiment, after ploughing and the use of a conventional seed treatment). The systemic seed dressing led to a higher and prolonged STB protection, with significant canopy greenness during ripening in all the production situations. In 2017, which suffered from high disease pressure, the seed treatment with systemic fungicide led to a significant increase in grain yield (+5%), compared to the conventional one. The combination of the systemic seed treatment and the triazole application at flowering guaranteed the highest control of both SLB and FHB, maximized grain yield, and minimized DON contamination. This study provides useful information that could be used to evaluate appropriate fungicide programs, based on a combination of seed and foliar treatments, for wheat yield and sanity in distinct SLB and FHB diseases pressure scenarios. Full article

Powdery mildew fungi (Erysiphales) are among the most common and important plant fungal pathogens. These fungi are obligate biotrophic parasites that attack nearly 10,000 species of angiosperms, including major crops, such as cereals and grapes. Although cultural and biological practices may reduce the risk of infection by powdery mildew, they do not provide sufficient protection. Therefore, in practice, chemical control, including the use of fungicides from multiple chemical groups, is the most effective tool for managing powdery mildew. Unfortunately, the risk of resistance development is high because typical spray programs include multiple applications per season. In addition, some of the most economically destructive species of powdery mildew fungi are considered to be high-risk pathogens and are able to develop resistance to several chemical classes within a few years. This situation has decreased the efficacy of the major fungicide classes, such as sterol demethylation inhibitors, quinone outside inhibitors and succinate dehydrogenase inhibitors, that are employed against powdery mildews. In this review, we present cases of reduction in sensitivity, development of resistance and failure of control by fungicides that have been or are being used to manage powdery mildew. In addition, the molecular mechanisms underlying resistance to fungicides are also outlined. Finally, a number of recommendations are provided to decrease the probability of resistance development when fungicides are employed. Full article

For two consecutive growing seasons (2017 and 2018), three different fungicide spray programs, each with five sprays from unrelated chemical groups, were evaluated for their effectiveness against apple scab (causal agent: Venturia inaequalis) in an experimental trial in Greece. The targeted application programs consisted of five sprays with protective and systemic fungicides from unrelated chemical groups, in alternation. The applications were started at the pink bud stage (a copper-based fungicide had previously been applied at the green bud stage) and completed at the second fruit fall to arrest the primary infections by ascospores. These five-spray programs were compared to the standard farmer practice (12 sprays per season), whereas untreated plots were used as controls. The timing of the applications was based: a) on the critical growth stage of the crop, and b) on the risk analysis for infection calculated by the software Field Climate, which incorporated meteorological data from the trial site. All the five-spray programs were of very high efficacy against apple scab, showing disease severity ratings on leaves and fruits below 1.88%. In both years, in the untreated control, the disease incidence and severity on leaves ranged from 96.5% to 99.3% and from 65.2% to 75.93%, respectively. The five-spray programs showed similar efficacy to the standard 12-application program in all cases. From the results, it becomes apparent that apple scab can be controlled effectively by five targeted applications with selected fungicides at critical growth stages of the crop. Full article