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Review

Basil Downy Mildew (Peronospora belbahrii): A Major Threat to Ocimum basilicum L. Production

by
Massimo Pugliese
1,*,
Giovanna Gilardi
1,
Angelo Garibaldi
1 and
Maria Lodovica Gullino
2
1
Interdepartmental Centre for Innovation in the Agri-Environmental Field Agroinnova, University of Turin, 10095 Grugliasco, TO, Italy
2
Department of Civil, Chemical and Environmental Engineering, University of Genoa, 16126 Genova, GE, Italy
*
Author to whom correspondence should be addressed.
Agriculture 2025, 15(19), 1999; https://doi.org/10.3390/agriculture15191999
Submission received: 4 August 2025 / Revised: 19 September 2025 / Accepted: 21 September 2025 / Published: 24 September 2025
(This article belongs to the Special Issue Agronomic Practices for Enhancing Quality and Yield of Aromatic and Medicinal Crops)
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Abstract

Basil (Ocimum basilicum L.), a key herb in Mediterranean cuisine, holds substantial economic and cultural value due to its aromatic and medicinal properties. Cultivated globally, particularly in Italy’s Liguria region, basil is consumed both fresh and processed, with pesto sauce as its most notable derivative. Despite its commercial success, basil production is significantly constrained by a broad spectrum of fungal pathogens, with Peronospora belbahrii, the causal agent of downy mildew, posing the most severe threat. This study aims to provide a comprehensive overview of basil’s disease susceptibility and control. Special emphasis is placed on the biology, epidemiology, global spread, and diagnosis of P. belbahrii, which has become a critical challenge for both conventional and organic farming systems. Disease management strategies, including cultural practices, genetic resistance, fungicide applications, resistance inducers, and biocontrol agents, are reviewed in detail. The development of downy mildew-resistant cultivars—although limited for PDO-designated Genovese basil—has emerged as the most sustainable control measure; however, the increasing genetic variability in P. belbahrii underscores the ongoing need for integrated pest management and resistant cultivar development. Seed health and quality remain the starting points of any fully integrated approach, although the suggested management measures for basil production should be combined with appropriate cultivation techniques aimed at reducing the relative humidity of the environment, while taking into account whether basil production takes place in open fields or under protection.

1. Introduction

Basil, an annual herbaceous plant belonging to the Lamiaceae family, is the most frequently used herb in Mediterranean cuisine. Native to tropical and subtropical Asia, its presence in Greek gardens was reported back in the 5th century BC [1]. Basil is cultivated in many countries, including the Americas, Italy, France, Greece, and Israel, and is used worldwide because of its aromatic and medicinal properties.
Peronospora belbahrii is an obligate biotrophic oomycete responsible for basil downy mildew, a highly destructive disease affecting sweet basil (Ocimum basilicum). Though symptoms of the disease were observed earlier, the pathogen was first formally described in 2001. Since then, it has rapidly emerged as a major global threat to basil cultivation, with confirmed outbreaks across Europe, North America, South America, the Middle East, Asia, and Africa [2].
The economic impact of P. belbahrii is severe. It causes yellowing, browning, and eventual defoliation of basil leaves, making the crop unmarketable and leading to significant yield losses (Figure 1). As a result, farmers have faced increased production costs due to reliance on fungicides, controlled-environment agriculture, and crop replacement.
The emergence of P. belbahrii has catalyzed research into its biology, host–pathogen interactions, and epidemiology. Efforts around breeding resistant basil cultivars, developing reliable diagnostic tools, and improving integrated disease management strategies have intensified [2].
This study aims to provide a comprehensive overview of basil’s disease susceptibility, with particular attention to basil downy mildew. It also aims to highlight the multifaceted efforts required to safeguard basil production and to provide a foundation for future research and control strategies.

2. Ocimum basilicum: Economic Context and Agronomic Relevance

2.1. Economic Importance at the Global Level

In 2020, basil had a market share of USD 57 million. This is projected to reach USD 62 million by 2026. North America represented 51.23% of the global market in 2019, while Asia–Pacific accounted for 37.87%, and Europe for 4.35% [3].
Italy is one of the top basil producers in the world, with approximately 800 ha [4]. The multiple cultivars grown and used in the Mediterranean area belong to Ocimum basilicum, which is one of the 64 species in the Ocimum genus [5]. O. basilicum, which is commonly known as sweet basil, is the most economically relevant species and is used for both fresh consumption and industrial food production, as well as for medicinal and cosmetic purposes.
The Liguria region (Northern Italy) is the most important area for high-quality basil cultivation in Italy, mainly due to its environmental characteristics, which give the fresh and processed product its unique organoleptic character that is recognized all over the world. O. basilicum cv. Genovese Gigante is the most frequently grown cultivar in this region, and is considered optimal for the preparation of pesto sauce [6].

2.2. Main Uses: Fresh Consumption, Processing (Pesto), and Essential Oils

The essential oils, which are mostly extracted from the aerial parts (flowers and leaves) of basil, are mainly used in the pharmaceutical industry. The medicinal and nutritional properties of basil are associated with its rich content of biologically active compounds, including phenolic acids (rosmarinic, chicoric, caffeic, and p-coumaric), flavonoids (quercetin), and anthocyanins, as well as vitamins and minerals [7]. Basil plants typically have an aniseed-like aroma and a sweet taste due to the presence of methyl chavicol (estragol) in the plant’s essential oils. Apart from methyl chavicol, the other essential oil components are linalool, eugenol, methyl eugenol, and geraniol, each of which is responsible for a different basil chemotype. Methyl eugenol and related alkenylbenzenes are considered naturally occurring genotoxic carcinogenic compounds, which pose some risks to human health [8]. However, recent studies have concluded that consumption of pesto sauces should be of concern only if consumed on a daily basis over long periods of time [8].
The considerable variation in essential oils has led to the cultivation of numerous cultivars with different scents. These cultivars have either been selected from the wild or obtained via cross-breeding [9]. ‘Genovese’ sweet basil, with its high content of linalool (46.7–53.9%) and eugenol (9.7–20.9%), is one of the most promising oil chemotype cultivars [10]. Light modification and micro-climate conditions, obtained by means of photo-selective netting, have improved the essential oil content and antioxidant capacity of basil [10].
Basil is used in both fresh and processed forms, mainly as pesto sauce. Pesto sauce is the second most frequently used fresh sauce in the world, after tomato sauce [11]. The global pesto market grew in 2021 and 2022, and is expected to continue growing, reaching USD 484.72 million in the 2022–2026 period [12]. The basil used in the processed food sector is cultivated in open fields at a sowing density of 15 to 30 kg of seeds per hectare, with at least 4–5 harvests per year [2,13]. This production takes place on large farms, with overhead sprinkler or drip irrigation and simple, mechanical harvesting.
The basil used for fresh consumption is mainly grown under protection in plastic tunnels or greenhouses. It is possible to control temperature and light, to a certain extent, in such cultivation systems, and to adopt prevention measures against pests and diseases [2,13]. Most of the basil used for fresh consumption has recently been grown under soilless conditions, particularly in hydroponic systems. When grown under soilless conditions, basil has faster production cycles and is harvested over shorter intervals compared with soil-based cultivation to ensure more tender leaves [14,15]. Hydroponic cultivation has also shown a higher sanitary quality than the traditional soil-based method, allowing plants to be ready with minimal processing due to the lack of soil residues, and with a lower risk of foodborne illnesses caused by the presence of microbes and heavy metals [16,17]. However, the presence of fungicide residues complicates the use of fungicides in both crop systems [18], thus making disease management more challenging.

2.3. Basil Is Affected by a Variety of Diseases

Basil is one of the crops that suffer most from fungal diseases [6]. This characteristic makes the basil crop a perfect model plant for short epidemiological studies. Basil cultivars vary in their susceptibility to diseases. Key factors influencing disease resistance include genetic diversity, leaf morphology, and chemical composition (e.g., essential oils). Some cultivars, such as ‘Genovese’ and ‘Sweet Basil,’ are more susceptible to diseases, while others, such as ‘Red-leaf’, ‘Lemon’, and ‘Hoary’, may exhibit greater resistance due to their unique traits.
Several soilborne pathogens have been reported to cause serious diseases in basil, including Fusarium oxysporum f. sp. basilici, which causes fusarium wilt, and Rhizoctonia solani and Pythium ultimum, which cause crown and root rot. Epidemiological considerations suggest that the rapid spread and long-distance transmission of Fusarium wilt in basil is due to the seedborne nature of the pathogen [19], and airborne inoculum, derived from macroconidial masses, is known to form on stem surfaces [20,21]. However, farmers have few economically sustainable control methods that they can use against these common soilborne pathogens [6,22].
Colletotrichum ocimi and Botrytis cinerea cause leaf spots, progressive leaf necrosis, and the defoliation of plants [6,23]. C. ocimi can cause significant losses under favorable conditions, starting from the nursery. B. cinerea, the causal agent of gray mold, is favored under high levels of humidity [24].
A. alternata has been observed on sweet basil in Europe, for example, in Italy [25], after being previously reported in California, Florida, Pakistan, Japan, and Israel [26]. The pathogen causes brown–black lesions, surrounded by a yellow halo, on older leaves, leading to the progressive defoliation of the plants, which, on occasion, can be followed by the death of the plant. Alternaria spp. are seedborne and may contaminate the surface of seeds produced by infected plants [27]. Moreover, almost all isolates of basil plants and seeds can produce Alternaria toxins (tenuazonic acid, alternariol, alternariol monomethyl ether, altenuene, and tentoxin) in vitro [28].
Stagonosporopis vannaccii has recently been observed on basil grown both under soilless conditions and in soil during a period of heavy rainfall followed by temperatures above the seasonal average and characterized by large day/night temperature variations [29]. Myrothecium leaf spot, which is caused by the seedborne pathogen Myrothecium, is more frequently associated with warmer environments and short wetting periods [30,31].
Although basil is affected by several diseases, downy mildew, caused by P. belbahrii, is the most important.

3. Basil Downy Mildew (Peronospora belbahrii): Biology, Epidemiology, and Global Spread

3.1. Biology and Epidemiology of Peronospora belbahrii

Sporulation in P. belbahrii typically occurs during periods of high humidity (≥85%) and moderate temperatures (15–25 °C), usually at night. The pathogen emerges from stomata on the abaxial (underside) surface of infected basil leaves (Figure 2), producing sporangiophores, which are branched structures that bear sporangia (Figure 3). These sporangia are lemon-shaped and colorless, and are the main dispersal units of the pathogen [26,32].
After dispersal, sporangia land on healthy basil leaves, typically on the lower surface. Under favorable conditions (high humidity and moderate temperatures), sporangia germinate. Infection occurs when the germ tube penetrates the basil leaf through a stomatal opening, entering the apoplast (the space between plant cells). Once inside, the pathogen develops a network of intercellular hyphae, which spread throughout the leaf tissue. As the infection progresses, chlorosis (yellowing) appears on the upper leaf surface, while grayish to purplish sporulation becomes visible on the underside. The incubation period (from infection to visible symptoms) is typically 5–10 days, depending on environmental conditions [26,32].
P. belbahrii colonizes the leaves, stems, and seeds of basil. Epidemiological considerations suggest that the rapid spread of the pathogen is caused or at least favored by its seedborne nature [33,34]. Seed contamination is thought to have been crucial in the introduction and spread of the pathogen across all the cultivated areas in Europe and the USA [33,34]. However, it is not clear to what extent P. belbahrii colonizes seeds or systemically infects host plants during natural infections [35]. P. belbahrii can spread systemically in basil plants, but it does not reach the roots or seeds, suggesting that the pathogen is seedborne but not seed-transmitted [36].
The pathogen may also be present in asymptomatic stems and leaves, thereby facilitating its unintended transport through host cuttings [35]. The pathogen can readily spread via wind-dispersed spores, which are produced in abundance [35].
In addition to O. basilicum, other members of the Lamiaceae family, including Salvia eigii, Salvia fruticosa, Salvia pinnata, some cultivars of Rosmarinus officinalis, Nepeta curviflora, Micromeria fruticosa, and Agastache spp., also host P. belbahrii, potentially facilitating its survival and spread. However, the role of such species in the epidemiology of basil downy mildew remains unclear [37] and needs further investigation. Moreover, some authors have reported that P. belbahrii is the causal agent of coleus and agastache downy mildew [38,39,40,41]. However, other studies have stated that the pathogen that causes coleus is a new species called P. choii [42], while the pathogen that causes agastache is a new species called P. monardae [43]. These have been distinguished from P. belbahrii based on molecular and morphological criteria [42].
Some environmental parameters, such as temperature, light, and leaf wetness, impact the timing of certain events in the life cycle of P. belbahrii. Garibaldi et al. [44] found that sporulation of P. belbahrii occurred when infected plants were incubated for at least 6 h in the dark in a humidity-saturated atmosphere at 20 °C. The shortest latent period from infection and sporulation was found to be 5 days at 25 °C under continuous light [35]. According to Elad et al. [13], downy mildew severity is negatively correlated with air temperature for values >25 °C and soil temperature (>21 °C) at a relative humidity of 65–85%. Temperatures exceeding 35 °C have been found to negatively affect the P. belbahrii infection process [35]. Leaf wetness for 24 h after the development of symptoms has been observed to cause prolific sporulation, resulting in the rapid spread of the pathogen throughout plantings during periods of high humidity, mild temperatures, poor air circulation, and extended durations of leaf wetness. Sporangia germinated 3 days after inoculation, and sporangiophores bearing sporangia were observed 7 days after inoculation when plants were grown under moist conditions and a photoperiod of 13 h of light and 11 h of darkness per day [45]. However, red light controlled basil downy mildew and improved the efficacy of chemical and organic fungicides [46].
Climate change is expected to have an impact on P. belbahrii. Indeed, high concentrations of CO2 (800 ppm) in controlled chambers have been observed to lead to increased downy mildew severity at temperatures of 18–26 °C, but not at higher temperatures of 26–30 °C [47].

3.2. Global Spread and Geographic Distribution of Peronospora belbahrii

Early reports of P. belbahrii infecting basil referred to the organism as Peronospora sp. and P. lamii [48,49]. However, further investigations showed that P. lamii was restricted to the downy mildew pathogen Lamium sp. [50,51]. The pathogen, first reported in Uganda [48], was sporadically observed in Africa in the twentieth century: in Tanzania in 1960 [52], then in Benin in 1998 [53]. The disease was first identified outside Africa in 2001, when it was reported in Switzerland [49,54]. Since the early 2000s, downy mildew has been reported in several countries throughout Europe (Switzerland in 2001, Italy in 2003, France in 2004, Belgium in 2004, Malta in 2005, Germany in 2009, Hungary and the United Kingdom in 2010, the Czech Republic in 2012, and Cyprus in 2014), in the USA (starting from 2007 in Florida and currently in a total of 42 States), in Argentina in 2008, Cuba in 2010, Canada in 2011, and Mexico in 2018, as well as in Africa (Tanzania and Cameroon) in 2008, Asia (Iran in 2006, Taiwan in 2009, China in 2014), Israel in 2011, and Australia in 2017 [26,32] (Table 1).
P. belbahrii’s sudden emergence and global spread are not the result of a single factor, but rather a convergence of international trade practices, climate suitability, greenhouse cultivation systems, and genetic vulnerability in its host crop. Understanding these dynamics is essential not only for managing basil downy mildew but also for anticipating similar outbreaks in other specialty crops.

4. Diagnosis

Accurate and timely detection of P. belbahrii is essential for effective disease management and containment. Various diagnostic methods are employed, ranging from traditional microscopic examination to advanced molecular assays. Each approach has distinct advantages and limitations, influencing their practical applicability depending on the context, resources, and objectives.
Microscopic methods, including direct observation of sporangiophores, sporangia, and hyphal structures on infected leaf tissue, remain the cornerstone for initial diagnosis. Simple staining techniques enhance visualization by highlighting pathogen structures within host tissues. These methods are rapid and cost-effective but suffer from low sensitivity, especially during early or latent infections when visible symptoms or sporulation are absent. Additionally, expertise is required to differentiate P. belbahrii structures from other similar oomycetes or fungal pathogens. A simple and effective staining method for the rapid microscopic detection of basil downy mildew on leaves has also been developed to facilitate control of the disease without the need for expensive and specialized equipment [84].
Molecular methods, particularly classic PCR and quantitative PCR (qPCR), enable highly sensitive and specific identification of P. belbahrii DNA in plant tissue, spores, or environmental samples. Diagnostic methods have been developed for the rapid detection of P. belbahrii in contaminated seed lots. Protocols have been defined using two sets of species-specific primers, based on the ITS1 and ITS2 regions, combined with SYBR-based qPCR protocols [34,59,85,86]. Primers targeting the ITS1 region of basil downy mildew have been used for the detection of specific pathogens on infected tissues or seeds using qPCR and classic PCR [34,54,86]. Further progress has been made with the development of other species-specific primers for use in conventional or real-time PCR protocols, which are effective for the rapid detection of the pathogen in contaminated seed lots or for the early detection of latent infections in seedlings [87]. However, these assays require specialized laboratory infrastructure, skilled personnel, and stringent protocols to prevent false positives due to contamination or false negatives due to inhibitors; moreover, DNA detection does not necessarily confirm pathogen viability or infectivity, limiting interpretation without complementary assays.
Emerging molecular techniques such as Loop-mediated Isothermal Amplification (LAMP) offer rapid, sensitive detection without the need for sophisticated thermocyclers, making them suitable for field diagnostics. While LAMP protocols for P. belbahrii are still under development and validation, they hold promise for point-of-care testing. Serological methods such as ELISA, commonly used for other plant pathogens, have limited application in oomycetes such as P. belbahrii, mainly due to the lack of specific antibodies and structural complexity.
High-throughput phenotyping methods, including automated imaging and spectral analysis, are being explored for the detection of subtle disease symptoms and for quantifying resistance levels non-invasively. These approaches, combined with machine learning algorithms, could enhance screening efficiency in breeding programs; however, they require substantial investment and validation.
Methods have also been developed to screen and evaluate the response of downy mildew at the cotyledon and true leaf growth stages to identify resistance to basil downy mildew [88]. Resistance screening typically involves bioassays where candidate basil cultivars or breeding lines are inoculated with P. belbahrii under controlled conditions. Disease severity is assessed visually or via molecular quantification of pathogen DNA. Phenotypic screening remains the most direct method, but it is labor-intensive and influenced by environmental variability. Molecular marker-assisted selection, once resistance genes or QTLs are identified, can accelerate breeding efforts, but is currently limited by the paucity of characterized resistance loci in basil [88].

5. Disease Management

Downy mildew continues to be the cause of major basil losses; therefore, it represents a serious concern for farmers, despite the many studies that have been conducted in different parts of the world. Its management is difficult for a number of reasons. First, basil, as a minor crop, suffers from a chronic lack of registered, traditional crop-protection products. Although fungicides are often not the most desirable solution, they are of crucial importance in integrated pest management programs [89]. The control of downy mildew in conventional farming, when carried out under protection, is mainly based on the adoption of appropriate cultivation practices aimed at reducing leaf wetness [90,91] and on the application of fungicides.

5.1. Preventive Measures (Seed Health, Cultural Practices, Genetic Control)

5.1.1. Seed Health

The availability of pathogen-free seeds is one of the most critical aspects in minimizing the initial pathogen inoculum in greenhouses. Seed companies are developing protocols for treating basil seeds using physical methods; unfortunately, basil seeds are not easily subject to hot-water treatment due to their intrinsic ability to form a hydrogel concomitant with moisture retention. Seed treatment with aerated steam, which requires sophisticated equipment, has been investigated on commercial farms in a few countries [92]. Dry hot air, applied at 65 °C for 10 min, is effective against both downy mildew and Fusarium wilt [93,94]. Several fungicides combined with thyme oil seed treatments have shown a significant reduction in seed infection, but the level of protection offered has only been partial [93].

5.1.2. Cultivation Practices

The adoption of cultivation techniques aimed at reducing relative humidity can be of great help in reducing the severity of downy mildew. Keeping humidity below 85% is considered crucial to managing the disease in protected cultivation. Reduction of the seeding density is of great interest, both in open fields and in protected cultivation, although yields may be reduced in greenhouses [95]. Indeed, the sowing density, or, in the case of potted plants, the choice of the planting pattern, significantly influences the relative humidity in the environment, a parameter that is closely correlated with the epidemiology of the pathogen [2,95]. The adoption of night ventilation and the use of infrared spectrum lamps, which limit pathogen sporulation, can significantly reduce the spread and severity of downy mildew [90,91]. These measures should be combined with a localized distribution of water for irrigation in fields or pots. La Placa et al. [96] found that localized irrigation resulted in a 23% reduction in disease severity compared to sprinkler distribution, and it also led to a more efficient use of water. A north–south orientation of tunnels leads to less severe basil downy mildew than an east–west orientation, although the yield is not affected [95]. Increasing air circulation and the use of gray, transparent, or yellow polyethylene mulch can also reduce downy mildew [95]. In addition, a sparse sowing density of basil varieties considered more resistant to the pathogen, combined with drip irrigation, could significantly reduce the spread of the pathogen [96].
Potassium fertilization and the application of Ca can significantly reduce the susceptibility of sweet basil to P. belbahrii [2,97,98], and can also have a positive effect against Sclerotinia sclerotiorum and Botrytis cinerea. Moreover, this combination can be integrated into management programs to achieve effective disease control [99,100]. Zn and Mn, when sprayed onto plants or applied as part of an irrigation solution, have been found to reduce the severity of P. belbahrii infection, as well as to alter plant host susceptibility, and thus require further investigation [97,98].

5.1.3. Resistant Cultivars

Genetic control can provide a reliable and long-term solution [35,80,101,102,103,104], despite the risk of selecting new pathogen races [105]. Selecting basil on the basis of its resistance to downy mildew is an active area of research, with scientists exploring various methods for developing resistant genotypes. Resistance to P. belbahrii has not been found for O. basilicum, but it has been found for other Ocimum species (O. americanum, O. canum, O. micranthemum) that represent exotic basil genotypes, which differ greatly in aroma and taste from sweet basil [88,106,107]. Basil species with higher stomatal densities are more susceptible to downy mildew [104], and leaf curvature and length affect the development and sporulation of downy mildew [104]. Breeding techniques, based on the CRISPR gene editing system [108], have resulted in the development of several basil cultivars with intermediate-to-high levels of downy mildew resistance.
Many of the developed varieties of basil are covered by patents, for example, “Rutgers DMR” (Obsession, Passion, Thunderstruck, and Devotion), “Prospera DMR F1” (Compact, Italian Broadleaf, and Premium), “Eleonora”, and “Everleaf” [103,109,110]. Thanks to considerable investments by numerous seed companies, it has been possible to obtain pathogen-tolerant varieties with organoleptic characteristics of the Genovese type, including cvs. Zeus, Diamante, Paoletto, Garibaldi, Gentile, Gemini, and Basiglio. Constant monitoring of the behavior of cultivars selected for pathogen tolerance in the field remains essential, as it is possible for the pathogen to evolve into different races, as evidenced in New Jersey [105] (Table 2). Variability in resistance has been observed among different basil cultivars under different environmental conditions and in various geographic locations, possibly due to the presence of different pathogenic races [37,96,105]. The genetic diversity of P. belbahrii is increasingly being recognized, with studies revealing wide genetic variation among isolates and its known ability to overcome the current resistant cultivars in Europe and the USA [111,112]. Resistant cultivars often carry the dominant R-gene, Pb1, which is derived from O. americanum. Additionally, notable resistant variants include some hybrids and cultivars carrying multiple quantitative trait loci [113]. A model that can predict the level of basil resistance to downy mildew has been developed and can be used to facilitate more timely and informed management decisions and to provide an important tool for plant breeders who are searching for improved downy mildew resistance [113]. The seeds of resistant cultivars are often more costly than those of susceptible cultivars. For example, the cost for 1 oz of Genovese seeds is USD 11.00 (average of 18,000 seeds), the Rutgers Devotion DMR resistant cultivar is USD 29.40 (19,900 seeds), and the Prospera cultivar is USD 27.55 (19,900 seeds) (High Mowing Organic Seeds, 2023 online catalogue) [3]. Basil seeds that are resistant to downy mildew are marketed at 10 times the cost of susceptible basil cultivars (30–40 €/kg) in Italian catalogues. However, the use of genetic resistance is not feasible for the Protected Designation of Origin (PDO) Genovese basil type, which is a protected variety of basil that is grown in Liguria (Italy) and is known for its unique aroma and flavor.
Host resistance is a preferred management practice. It is more cost-effective than chemical control (the average cost for a single fungicide application within the conventional program is USD 55), despite the higher cost of seeds [3].

5.2. Control Measures: Fungicides, Resistance Inducers, Biocontrol Agents, and Plant Extracts

5.2.1. Fungicides

Several chemical classes of fungicides with different modes of action have been investigated for the control of basil downy mildew [80,93,114,115,116]. The three most important single-site compounds used against this pathogen are the mefenoxam of phenylamides, the azoxystrobin of the quinone outside inhibitors (QoIs), and the mandipropamid of the carboxylic acid amide (CAA) group. Mefenoxam was the first chemical with a specific mode of action registered for use on basil in the Mediterranean area in 2004 [114], and is now widely applied. Azoxystrobin is a broad-spectrum fungicide that acts in a translaminar way, shows good control activity, and is used as a preventive treatment because it can effectively reduce the germination of spores [117]. Mandipropamid, a broad-spectrum chemical that is active against several oomycetes, provides good translaminar, but limited curative and antisporulant activity; it also protects new growth [118]. Since 2014, fluopicolide, which belongs to the acylpicolide and dimethomorph (CAA) group, has received increasing attention in several EU countries. As a result of the ongoing review and ban on environmentally harmful molecules—for example, dimethomorph, which cannot be used in Europe since February 2025 (Regulation EU 2023/918)—new active ingredients are required. In the USA, for example, oxathiapoprolin is the first member of a new class of piperidinyl thiazole isoxazoline fungicides that have shown very good activity against downy mildews. It is used in the USA on basil grown in fields and on protected crops [89,119], but is not registered for use on minor crops, such as basil, in Europe. Various products have been tested alone or in rotation around the world with the aim of finding an effective solution to the pathogen, with sometimes unconfirmed results [2,80,89,110,115,116].
In trials carried out on artificially inoculated basil plants grown under protection, the greatest reduction in disease incidence and severity was found for treatments that included metalaxyl-M + copper hydroxide, potassium phosphite, mandipropanid, and azoxystrobin [115]. The glucohumate activator complex and acibenzolar-S-methyl also provided significant disease control 20 days after the final treatment [115]. It is recommended that acibenzolar-S-methyl be applied to 5- to 7-week-old plants before pathogen infection to reduce the growth of downy mildew on basil [120].
The use of chemicals in the field is complicated by the continuous harvesting of this crop, by the seedborne nature of the pathogen, and by the high risk of the development of strains that are resistant to the fungicides through specific modes of action, as already observed in the case of phenylamides in Israel [60] and Italy [121]. Moreover, contaminated basil seeds are a potential source of the mefenoxam-resistant inoculum of P. belbahrii [121].
An increasing number of producers, driven by the demands of increasingly health-sensitive consumers, have adopted organic production techniques for this species [122]. Since synthetic fungicides are not permitted in organic farming, other products, such as resistance inducers, biocontrol agents, and plant extracts, are required.

5.2.2. Resistance Inducers

Acibenzolar-S-methyl (ASM), which was developed as a systemic acquired resistance (SAR) activator, has been found to significantly reduce basil downy mildew, compared to a non-treated control, when sprayed or drenched pre- or pre- + post-inoculation at rates of 25–400 mg/L [123]. In the aforementioned experiment, acibenzolar-S-methyl was more effective than DL-3-aminobutyric acid, isonicotinic acid, salicylic acid, or sodium salicylate [123]. In another experiment, basil plants treated with ASM under red light had significantly fewer numbers of P. belbahrii sporangia compared to those under dark conditions that received the same fungicide treatment [46].
Phosphite salt-based products have also been reported to be effective against the disease [2,80,115,116], probably due to their ability to activate plant defense by inducing the synthesis and translocation of phytoalexins, as shown in the case of Phytophthora infestans on tomato [124]. The phosphate-mediated induction of resistance is also associated with increased activities of phenylalanine ammonia-lyase (PAL), peroxidase (POD), and lipoxygenase, as shown in the case of powdery mildew of barley [125]. However, in some cases, mono- and di-potassium salts of phosphorous acid provided a degree of control that was not as high as other tested fungicides [126].
Among the various salts, the effect of potassium bicarbonate has also been investigated against downy mildew in basil; however, it provided limited control and variable results [80], while silicates, applied to basil grown under soilless conditions, controlled other diseases [127].
Among the polysaccharides, laminarin, a resistance-inducer primarily extracted from brown seaweed, was found to be ineffective when applied to a susceptible field-grown basil cultivar, but moderately effective when applied to a resistant cultivar [128].
The best approach for the management of downy mildew appears to be a combination of different methods; that is, starting with seed treatment, followed by application of a limited number of foliar sprays of the most effective products with different modes of action, focusing on the type of application, the formulation, and use in integrated pest management [2] (Table 3).
Some of the methods that have proved effective against basil downy mildew are also effective against other foliar diseases (gray mold, anthracnose) [13,24,129].

5.2.3. Biocontrol Agents and Plant Extracts

Biological products, which contain microbes or other natural substances as their active ingredients and are generally approved for organic production, have shown very limited effects against P. belbahrii in several studies [96,130].
The Bacillus subtilis strain QST713 and thyme oil extract provided only partial efficacy in a greenhouse trial [115] (Table 4). In trials conducted under controlled greenhouse conditions, calcium and orange oil were used after fungicides (pyraclostrobin + dimethomorph, fluopicolide, and mandipropamid) to increase planting densities [2]. The efficacy of calcium and orange oil, used alone or after fungicide application, was significantly better at a seed density of 600–750 plants/m2 than at the density conventionally adopted in the field (1600–1700 plants/m2) [2].
Basil plants treated with sesame oil under red light showed a significantly reduced number of P. belbahrii sporangia compared with those that had received the same fungicide treatment under dark conditions in a greenhouse [46].
Bacillus amyloliquefaciens, strain D747, amino acids, and proteins [96], as well as Bacillus subtilis MB1600, Streptomyces lydicus, Bacillus amyloliquefaciens, and plant extracts (sesame oil, polyoxin D zinc salt, citric acid, Reynoutria sachalinensis extract, and neem oil) applied to susceptible basil cultivars were found to be insufficient in controlling the pathogen in field trials [130].
Unfortunately, organic management of basil downy mildew relies on environmental changes (to minimize the presence of water on the plant canopy), the use of resistant cultivars, and the employment of product-based copper salts.

6. Challenges and Perspectives

Despite significant advances in understanding P. belbahrii and managing basil downy mildew, several critical knowledge gaps and challenges remain that hinder effective, long-term control of this devastating pathogen.
A fundamental limitation is the incomplete understanding of the pathogen’s biology and epidemiology. Key aspects such as the precise mechanisms underlying overwintering, survival outside host plants, and the full range of environmental factors influencing sporulation and infection remain underexplored. This lack of detailed knowledge complicates predictive modeling and the development of targeted intervention strategies.
Diagnostic limitations also present a significant hurdle. While molecular methods such as qPCR have improved sensitivity and specificity, they cannot unequivocally distinguish between viable and non-viable pathogen propagules, which is critical for accurate disease forecasting and seed health assessment. The development and validation of rapid, cost-effective, and field-deployable diagnostic tools, such as refined LAMP assays or immunological tests, remain a priority.
In the realm of host resistance, the durability and genetic basis of resistance to P. belbahrii are poorly characterized. Most commercial basil cultivars lack robust resistance, and resistance identified in breeding programs may be overcome by evolving pathogen populations, as observed with other oomycetes. Identifying and incorporating durable resistance genes or quantitative trait loci through advanced genomic and breeding approaches is urgently needed to reduce reliance on chemical controls.
Fungicide resistance is an emerging threat. The widespread use of oomycete-targeting fungicides, such as metalaxyl and related compounds, has led to the development of resistance in many pathogens that cause downy mildew. Monitoring P. belbahrii populations for fungicide sensitivity, understanding resistance mechanisms, and implementing integrated fungicide stewardship programs will be essential in maintaining chemical efficacy.
Looking forward, a multifaceted research agenda should focus on closing these gaps. This includes detailed studies on pathogen population genetics and evolution to track the emergence of virulent or fungicide-resistant strains; improved epidemiological models incorporating microclimatic data to optimize intervention timing; and development of integrated management strategies combining cultural practices, resistant cultivars, and precision fungicide applications.
Furthermore, fostering international collaboration and knowledge-sharing will be vital given the pathogen’s rapid global spread. Investment in extension services and farmer education can promote the adoption of best practices and early detection, limiting outbreaks.

7. Conclusions

The current ability to manage basil downy mildew is the result of improved knowledge of the biology and epidemiology of the pathogen, the presence on the market of cultivars with a good-to-excellent level of resistance, and the availability of new fungicides and biostimulant products. Advances in molecular diagnostics and microscopic detection have improved early and accurate identification, enabling more timely interventions; nonetheless, complete control remains elusive. Seed health and quality remain the starting points of any fully integrated approach; however, the currently available seed treatment methods do not completely eradicate the pathogen from seeds, even though some varieties of sweet basil of commercial interest offer resistance to downy mildew. These challenges highlight the pathogen’s resilience and the complexities of its epidemiology, particularly in diverse cultivation systems ranging from open fields to controlled environments.
Research offers solutions that are suitable for and/or adaptable to different types of farming systems; that is, from conventional to organic farming practices. Chemical and biostimulant products provide farmers with additional means of reducing disease pressure. However, reliance on fungicides carries the inherent risk of resistance development, necessitating their use within a broader integrated framework. Cultural practices that reduce environmental conditions favorable to the pathogen—such as lowering humidity and optimizing plant spacing—are vital complements to genetic and chemical controls, particularly in protected cultivation where microclimate management is feasible.
Looking forward, a holistic and adaptable approach tailored to diverse agricultural contexts is essential. This approach should integrate continuous monitoring, resistant-cultivar deployment, environmentally mindful cultivation techniques, and innovative diagnostics. Addressing existing knowledge gaps in pathogen biology, resistance durability, and fungicide sensitivity will be critical to sustaining long-term management success.
Ultimately, safeguarding global basil production against downy mildew will require coordinated research efforts, extension services, and international collaboration. By combining fundamental science with practical solutions, the industry can move toward resilient, sustainable basil cultivation that meets growing market demands while mitigating the threat of P. belbahrii.

Author Contributions

Conceptualization, M.P., G.G., A.G. and M.L.G.; writing—original draft preparation, M.P., G.G. and M.L.G.; writing—review and editing, M.P., G.G., A.G. and M.L.G.; supervision, A.G. and M.L.G.; funding acquisition, M.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the European Union Next-Generation EU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR)-MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.4 -D.D. 1032 17 June 2022, CN00000022), Spoke 6. This manuscript reflects the authors’ views and opinions only, and neither the European Union nor the European Commission can be held responsible for them.

Acknowledgments

The authors would like to thank the anonymous reviewers for their helpful comments and feedback.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Dalby, A. Siren Feasts: A History of Food and Gastronomy in Greece; Routledge: London, UK, 1996; pp. 1–352. [Google Scholar]
  2. Gilardi, G.; Garibaldi, A.; Gullino, M.L. Integrated management of downy mildew of basil. Crop Prot. 2020, 137, 105202. [Google Scholar] [CrossRef]
  3. McGrath, M.T. Sweet basil cultivars resistant to downy mildew evaluated under open field conditions. Crop Prot. 2024, 184, 106815. [Google Scholar] [CrossRef]
  4. Macaluso, D.; Licciardo, F.; Carbone, K. Farming of Medicinal and Aromatic Plants in Italy: Structural Features and Economic Results. Agriculture 2024, 14, 151. [Google Scholar] [CrossRef]
  5. Paton, A.; Harley, R.M.; Harley, M.M. Ocimum: An overview of classification and relationships. In Basil; CRC Press: Boca Raton, FL, USA, 1999; pp. 11–46. [Google Scholar]
  6. Garibaldi, A.; Gullino, M.L.; Minuto, G. Diseases of basil and their management. Plant Dis. 1997, 81, 124–132. [Google Scholar] [CrossRef][Green Version]
  7. Ciriello, M.; Kyriacou, M.C.; De Pascale, S.; Rouphael, Y. An appraisal of critical factors configuring the composition of basil in minerals, bioactive secondary metabolites, micronutrients and volatile aromatic compounds. J. Food Compos. Anal. 2022, 111, 104582. [Google Scholar] [CrossRef]
  8. Al-Malahmeh, A.J.; Al-Ajlouni, A.M.; Wesseling, S.; Vervoort, J.; Rietjens, I.M.C.M. Determination and risk assessment of naturally occurring genotoxic and carcinogenic alkenylbenzenes in basil-containing sauce of pesto. Toxicol. Rep. 2016, 4, 1–8. [Google Scholar] [CrossRef] [PubMed]
  9. Grayer, R.J.; Kite, G.C.; Goldstone, F.J.; Bryan, S.E.; Paton, A.; Putievsky, E. Infraspecific taxonomy and essential oil chemotypes in sweet basil (Ocimum basilicum). Phytochemistry 1996, 43, 1033–1039. [Google Scholar] [CrossRef]
  10. Castronuovo, D.; Russo, D.; Libonati, R.; Faraone, I.; Candido, V.; Picuno, P.; Andrade, P.; Valentão, P.; Milella, L. Influence of shading treatment on yield, morphological traits and phenolic profile of sweet basil (Ocimum basilicum L.). Sci. Hortic. 2019, 254, 91–98. [Google Scholar] [CrossRef]
  11. Masino, F.; Foca, G.; Ulrici, A.; Arru, L.; Antonelli, A. A chemometric study of pesto sauce appearance and of its relation to pigment concentration. J. Sci. Food Agric. 2009, 88, 1335–1343. [Google Scholar] [CrossRef]
  12. Research and Markets. Global Pesto Sauces Market 2022–2026. Report ID: 5574291. Available online: https://www.researchandmarkets.com/reports/5574291/global-pesto-sauces-market-2022-2026 (accessed on 3 August 2025).
  13. Elad, Y.; Omer, C.; Nisan, Z.; Harari, D.; Goren, H.; Adler, U.; Silverman, D.; Biton, S. Passive heat treatment of sweet basil crops suppresses Peronospora belbahrii downy mildew. Ann. Appl. Biol. 2016, 168, 373–389. [Google Scholar] [CrossRef]
  14. Khater, E.S.; Bahnasawy, A.; Abass, W.; Morsly, O.M.; El-Ghobashy, H.; Shanban, Y.; Egela, M. Production of basil (Ocimum basilicum L.) under different soilless cultures. Sci. Rep. 2021, 11, 12754. [Google Scholar] [CrossRef] [PubMed]
  15. Sowmya, R.S.; Warke, V.G.; Mahajan, G.B.; Annapure, U.S. Quality and shelf-life assessment of pesto prepared using herbs cultivated by hydroponics. Int. J. Gastron. Food Sci. 2022, 30, 100608. [Google Scholar] [CrossRef]
  16. Sathyanarayana, S.R.; Warke, V.G.; Mahajan, G.B.; Annapure, U.S. Comparative studies of microbial and heavy metal safety assessment of the herbs cultivated in hydroponically and regular soil system. J. Food Saf. 2021, 41, e12936. [Google Scholar] [CrossRef]
  17. De Bruin, W.; Otto, D.; Korsten, L. Microbiological status and food safety compliance of commercial basil production systems. J. Food Prot. 2016, 79, 43–50. [Google Scholar] [CrossRef]
  18. Rheinholds, I.; Pugajeva, I.; Bavrins, K.; Kuckovska, G.; Bertkevics, V. Mycotoxins, pesticides and toxic metals in commercial spices and herbs. Food Addit. Contam. Part B Surveill. 2017, 10, 5–10. [Google Scholar] [CrossRef]
  19. Elmer, W.H.; Wick, R.L.; Haviland, P. Vegetative compatibility among Fusarium oxysporum f. sp. basilicum isolates recovered from basil seed and infected plants. Plant Dis. 1994, 78, 789–791. [Google Scholar] [CrossRef]
  20. Gamliel, A.; Katan, T.; Yunis, H.; Katan, J. Fusarium wilt and crown rot of sweet basil: I. Involvement of soilborne and airborne inoculum. Phytopathology 1996, 86, 56–62. [Google Scholar] [CrossRef]
  21. Gamliel, A.; Yarden, O. Diversification of diseases affecting herb crops in Israel accompanies the increase in herb crop production. Phytoparasitica 1998, 26, 53–58. [Google Scholar] [CrossRef][Green Version]
  22. Chellemi, D.O.; Gamliel, A.; Katan, J.; Subbarao, L.V. Development and deployment of systems-based approaches for the management of soilborne plant pathogens. Phytopathology 2016, 106, 216–225. [Google Scholar] [CrossRef]
  23. Cacciola, S.O.; Gilardi, G.; Faedda, R.; Schena, L.; Pane, A.; Garibaldi, A.; Gullino, M.L. Characterization of Colletotrichum ocimi population associated with black spot of sweet basil (Ocimum basilicum) in Northern Italy. Plants 2020, 9, 654. [Google Scholar] [CrossRef]
  24. Sharabani, G.; Shtienberg, D.; Elad, Y.; Dinoor, A. Epidemiology of Botrytis cinerea in sweet basil and implications for disease management. Plant Dis. 1999, 83, 554–560. [Google Scholar] [CrossRef]
  25. Garibaldi, A.; Gilardi, G.; Bertoldo, C.; Gullino, M.L. First report of a leaf spot of sweet basil (Ocimum basilicum) caused by Alternaria alternata in Italy. J. Plant Pathol. 2011, 93, S71. [Google Scholar]
  26. Farr, D.F.; Rossman, A.Y. Fungal Databases, U.S. National Fungus Collections, ARS, USDA. Available online: https://fungi.ars.usda.gov/ (accessed on 20 April 2025).
  27. Gilardi, G.; Gullino, M.L.; Garibaldi, A. Occurrence of Alternaria spp. in the seeds of basil and its pathogenicity. J. Plant Pathol. 2013, 95, 41–47. [Google Scholar]
  28. Siciliano, I.; Franco Ortega, S.; Gilardi, G.; Bosio, P.; Garibaldi, A.; Gullino, M.L. Molecular phylogeny and characterization of secondary metabolite profile of plant pathogenic Alternaria species isolated from basil. Food Microbiol. 2018, 73, 264–274. [Google Scholar] [CrossRef]
  29. Guarnaccia, V.; Gilardi, G.; Napoletano, E.; Garibaldi, A.; Gullino, M.L. A new foliar disease of sweet basil caused by Stagonosporopsis vannaccii. J. Plant Pathol. 2022, 4, 1491–1498. [Google Scholar] [CrossRef]
  30. Matic, S.; Gilardi, G.; Gullino, M.L.; Garibaldi, A. Emergence of leaf spot disease on leafy vegetable and ornamental crops caused by Paramyrothecium and Albifimbria species. Phytopathology 2019, 109, 1053–1061. [Google Scholar] [CrossRef]
  31. Nguyen, T.H.; Mathur, S.B.; Neergaard, P. Seed-borne species of Myrothecium and their pathogenic potential. Trans. Br. Mycol. Soc. 1973, 61, 347–354. [Google Scholar] [CrossRef]
  32. Crouch, J.A. Peronospora belbahrii (basil downy mildew). CABI Compend. 2020, 118352. [Google Scholar] [CrossRef]
  33. Garibaldi, A.; Minuto, G.; Bertetti, D.; Gullino, M.L. Seed transmission of Peronospora sp. of basil. J. Plant Dis. Prot. 2004, 111, 465–469. [Google Scholar]
  34. Farahani-Kofoet, D.R.; Römer, P.; Grosch, R. Systemic spread of downy mildew in basil plants and detection of the pathogen in seed and plant samples. Mycol. Prog. 2012, 11, 961–966. [Google Scholar] [CrossRef]
  35. Cohen, Y.; Vaknin, M.; Ben-Naim, Y.; Rubin, A.E. Epidemiology of basil downy mildew. Phytopathology 2017, 107, 1149–1160. [Google Scholar] [CrossRef] [PubMed]
  36. Falach-Block, L.; Ben-Naim, Y.; Cohen, Y. Investigation of seed transmission in Peronospora belbahrii, the causal agent of basil downy mildew. Agronomy 2019, 9, 205. [Google Scholar] [CrossRef]
  37. Naim, Y.B.; Falach-Block, L.; Ben-Daniel, B.H.; Cohen, Y. Host range of Peronospora belbahrii, causal agent of basil downy mildew, in Israel. Eur. J. Plant Pathol. 2019, 155, 789–799. [Google Scholar] [CrossRef]
  38. Henricot, B.; Denton, J.; Scrace, J.; Barnes, A.V.; Lane, C.R. Peronospora belbahrii causing downy mildew disease on Agastache in the UK: A new host and location for the pathogen. Plant Pathol. 2010, 59, 801. [Google Scholar] [CrossRef]
  39. Ito, Y.; Takeuchi, T.; Matsushita, Y.; Chikuo, Y.; Satou, M. Downy mildew of coleus caused by Peronospora belbahrii in Japan. J. Gen. Plant Pathol. 2015, 81, 328–330. [Google Scholar] [CrossRef]
  40. Rivera, Y.; Salgado-Salazar, C.; Creswell, T.C.; Ruhl, G.; Crouch, J.A. First report of downy mildew caused by Peronospora sp. on Agastache sp. in the United States. Plant Dis. 2016, 100, 1249–1250. [Google Scholar] [CrossRef]
  41. Gorayeb, E.S.; Pieroni, L.P.; Cruciol, G.C.D.; Pieri, C.; Dovigo, L.H.; Pavan, M.A.; Kurozawa, C.; Krause-Sakate, R. First report of downy mildew on coleus (Plectranthus spp.) caused by Peronospora belbahrii sensu lato in Brazil. Plant Dis. 2020, 104, 294. [Google Scholar] [CrossRef]
  42. Hoffmeister, M.; Ashrafi, S.; Thines, M.; Maier, W. Two new species of the Peronospora belbahrii species complex, Pe. choii sp. nov. and Pe. salvia-pratensis sp. nov., and a new host for Pe. salviae-officinalis. Fungal Syst. Evol. 2020, 6, 39–53. [Google Scholar] [CrossRef] [PubMed]
  43. Salgado-Salazar, C.; LeBlanc, N.; Wallace, E.C.; Daughtrey, M.L.; Crouch, J.A. Peronospora monardae, Hyaloperonospora daughtreyae, and H. iberidis: New species associated with downy mildew diseases affecting ornamental plants in the United States. Eur. J. Plant Pathol. 2020, 157, 311–326. [Google Scholar] [CrossRef]
  44. Garibaldi, A.; Bertetti, D.; Gullino, M.L. Effect of leaf wetness duration and temperature on infection of downy mildew (Peronospora sp.) of basil. J. Plant Dis. Prot. 2007, 114, 6–8. [Google Scholar] [CrossRef]
  45. Zhang, G.; Thompson, A.; Schisler, D.; Johnson, E.T. Characterization of the infection process by Peronospora belbahrii on basil by scanning electron microscopy. Heliyon 2019, 5, e01117. [Google Scholar] [CrossRef]
  46. Patel, J.S.; Zhang, S.; McGrath, M.T. Red light increases suppression of downy mildew in basil by chemical and organic products. J. Phytopathol. 2016, 164, 1022–1029. [Google Scholar] [CrossRef]
  47. Gilardi, G.; Pugliese, M.; Chitarra, W.; Ramon, I.; Gullino, M.L.; Garibaldi, A. Effect of elevated atmospheric CO2 and temperature increases on the severity of basil downy mildew caused by Peronospora belbahrii under phytotron conditions. J. Phytopathol. 2016, 164, 114–121. [Google Scholar] [CrossRef]
  48. Hansford, C.G. Annual report of the mycologist. Rev. Appl. Mycol. 1933, 12, 421–422. [Google Scholar]
  49. Lefort, F.; Gigon, V.; Amos, B. Le mildiou s’étend. Déjà détecté dans de nombreux pays européens, Peronospora lamii, responsable du mildiou de basilic, a été observé en Suisse dans la région lémanique. Réussir Fruits Légumes 2003, 223, 66. [Google Scholar]
  50. Liberato, J.R.; Forsberg, L.; Grice, K.R.; Shivas, R.G. Peronospora lamii on Lamiaceae in Australia. Australas. Plant Pathol. 2006, 35, 367–368. [Google Scholar] [CrossRef]
  51. Thines, M.; Buaya, A.; Ploch, S.; Naim, Y.B.; Cohen, Y. Downy mildew of lavender caused by Peronospora belbahrii in Israel. Mycol. Progr. 2020, 19, 1537–1543. [Google Scholar] [CrossRef]
  52. Riley, E.A. A revised list of plant diseases in Tanganyika Territory. Mycol. Pap. 1960, 75, 42. [Google Scholar]
  53. Gumedzoe, M.Y.D.; Hemou, P.; Lepage, A.; Lecat, N. Inventaire et identification de Peronospora lamii (Al. Br.) de By, agent causal du mildiou du basilic (Ocimum basilicum) dans les exploitations de Gyma Cultures. In Proceedings of the Les VIIIe Journées Scientifiques de l’Université du Bénin, University of Lomé, Benin, Togo, 11–15 May 1998. [Google Scholar]
  54. Belbahri, I.; Calmin, G.; Pawlowski, J.; Lefort, F. Phylogenetic analysis and real time PCR detection of a presumably undescribed Peronospora species on sweet basil and sage. Mycol. Res. 2005, 109, 1276–1287. [Google Scholar] [CrossRef]
  55. Voglmayr, H.; Piątek, M. Peronospora causing downy mildew disease of sweet basil newly reported in Cameroon. Plant Pathol. 2009, 58, 805. [Google Scholar] [CrossRef]
  56. McLeod, A.; Coertze, S.; Mostert, L. First report of a Peronospora species on sweet basil in South Africa. Plant Dis. 2006, 90, 1115. [Google Scholar] [CrossRef]
  57. Hu, B.; Li, Z.; Hu, M.; Sun, H.; Zheng, J.; Diao, Y. Outbreak of downy mildew caused by Peronospora belbahrii on Ocimum basilicum var. polosum in China. New Dis. Rep. 2018, 37, 1. [Google Scholar] [CrossRef]
  58. Kong, X.Y.; Wang, S.; Wan, S.L.; Xiao, C.L.; Luo, F.; Liu, Y. First report of downy mildew on basil (Ocimum basilicum) in China. Plant Dis. 2015, 99, 1642. [Google Scholar] [CrossRef]
  59. Khateri, H.; Calmin, G.; Moarrefzadeh, N.; Belbahri, L.; Lefort, F. First report of downy mildew caused by Peronospora sp. on basil in northern Iran. J. Plant Pathol. 2007, 89, S70. [Google Scholar]
  60. Cohen, Y.; Vaknin, M.; Ben-Naim, Y.; Rubin, A.E.; Galperin, M.; Silverman, D.; Bitton, S.; Adler, U. First report of the occurrence and resistance to mefenoxam of Peronospora belbahrii, causal agent of downy mildew of basil (Ocimum basilicum) in Israel. Plant Dis. 2013, 97, 692. [Google Scholar] [CrossRef]
  61. EPPO. Peronospora belbahrii, Distribution. EPPO Global Database. 2021. Available online: https://gd.eppo.int/taxon/PEROBE/distribution (accessed on 4 August 2025).
  62. Choi, Y.J.; Choi, I.Y.; Lee, K.J.; Shin, H.D. First report of downy mildew caused by Peronospora belbahrii on sweet basil (Ocimum basilicum) in Korea. Plant Dis. 2016, 100, 2335. [Google Scholar] [CrossRef]
  63. Chen, C.H.; Huang, J.H.; Hsieh, T.F. First report of Peronospora belbahrii causing downy mildew on basil. Plant Pathol. Bull. 2010, 19, 177–180. [Google Scholar]
  64. CABI; EPPO. Peronospora belbahrii [Distribution map]. In Distribution Maps of Plant Diseases, 1st ed.; CABI International: Wallingford, UK, 2015; p. Map 1177. Available online: https://www.cabidigitallibrary.org/doi/10.1079/DMPD/20153399811 (accessed on 4 August 2025).
  65. Hafellner, J. Der Falsche Mehltaupilz auf Basilikum nun auch in Österreich eingeschleppt. Fritschiana 2006, 54, 29–34. [Google Scholar]
  66. Coosemans, J. First report of Peronospora lamii, downy mildew on basil (Ocimum basilicum) in Belgium. Parasitica 2004, 60, 27. [Google Scholar]
  67. Novak, A.; Sever, Z.; Ivić, D.; Čajkulić, A.M. Plamenjača bosiljka (Peronospora belbahrii)—Destruktivna bolest u proizvodnji bosiljka. Glas. Biljn. Zaštite 2016, 16, 544–547. [Google Scholar]
  68. Kanetis, L.; Vasiliou, A.; Neophytou, G.; Samouel, S.; Tsaltas, D. First report of downy mildew caused by Peronospora belbahrii on sweet basil (Ocimum basilicum) in Cyprus. Plant Dis. 2014, 98, 283. [Google Scholar] [CrossRef]
  69. Šafránková, I.; Holková, L. The first report of downy mildew caused by Peronospora belbahrii on sweet basil in greenhouses in the Czech Republic. Plant Dis. 2014, 98, 1579. [Google Scholar] [CrossRef]
  70. Petrželová, I.; Kitner, M.; Doležalová, I.; Ondřej, V.; Lebeda, A. First report of basil downy mildew caused by Peronospora belbahrii in the Czech Republic. Plant Dis. 2015, 99, 418. [Google Scholar] [CrossRef]
  71. Garibaldi, A.; Minuto, A.; Gullino, M.L. First report of downy mildew caused by Peronospora sp. on basil (Ocimum basilicum) in France. Plant Dis. 2005, 89, 683. [Google Scholar] [CrossRef]
  72. Nagy, G.; Horváth, A. Occurrence of downy mildew caused by Peronospora belbahrii on sweet basil in Hungary. Plant Dis. 2011, 95, 1034. [Google Scholar] [CrossRef] [PubMed]
  73. Garibaldi, A.; Minuto, A.; Minuto, G.; Gullino, M.L. First report of downy mildew of basil (Ocimum basilicum) in Italy. Plant Dis. 2004, 88, 312. [Google Scholar] [CrossRef]
  74. Porta-Puglia, A.; Mifsud, D. First record of downy mildew caused by Peronospora sp. on basil in Malta. J. Plant Pathol. 2006, 88, 124. [Google Scholar]
  75. Gómez Tenorio, M.A.; Lupión Rodríguez, B.; Boix Ruiz, A.; Ruiz Olmos, C.; Moreno Díaz, A.; Marín Guirao, J.I. El mildiu: Nueva enfermedad de la albahaca en España. Phytoma Esp. 2016, 282, 48–52. [Google Scholar]
  76. Heller, W.; Baroffio, C. Le mildiou (Peronospora lamii) du basilic progresse! Gemüsebau/Maraîcher 2003, 8, 12–13. [Google Scholar]
  77. Webb, K.; Sansford, C.; MacLeod, A.; Matthews-Berry, S. Rapid Assessment of the Need for a Detailed Pest Risk Analysis for Peronospora belbahrii. UK Risk Register Details for Peronospora belbahrii. UK Plant Health Risk Register (DEFRA). 2012. Available online: https://planthealthportal.defra.gov.uk/pests-and-diseases/uk-plant-health-risk-register/downloadExternalPra.cfm?id=3901 (accessed on 3 August 2025).
  78. Saude, C.; Westerveld, S.; Filotas, M.; McDonald, M.R. First report of downy mildew caused by Peronospora belbahrii on basil (Ocimum spp.) in Ontario. Plant Dis. 2013, 97, 1248. [Google Scholar] [CrossRef]
  79. Joshi, V.; Jeffries, M.; Jesperson, G. Canadian Plant Disease Survey. Can. Plant Dis. Surv. 2013, 93, 7–32. [Google Scholar]
  80. Wyenandt, C.A.; Simon, J.E.; Pyne, R.M.; Homa, K.; McGrath, M.T.; Zhang, S.; Raid, R.N.; Ma, L.-J.; Wick, R.; Guo, L.; et al. Basil downy mildew (Peronospora belbahrii): Discoveries and challenges relative to its control. Phytopathology 2015, 105, 885–894. [Google Scholar] [CrossRef]
  81. Ronco, L.; Rollán, C.; Choi, Y.J.; Shin, H.D. Downy mildew of sweet basil (Ocimum basilicum) caused by Peronospora sp. in Argentina. Plant Pathol. 2009, 58, 395. [Google Scholar] [CrossRef]
  82. Silva, A.L.; Mansur, P.S.C.; Barreto, R.W.; Salcedo-Sarmiento, S. Peronospora belbahrii causes downy mildew on Ocimum basilicum in Brazil. Australas. Plant Dis. Notes 2019, 14, 37. [Google Scholar] [CrossRef]
  83. Martinez-de la Parte, E.; Perez-Vicente, L.; Bernal, B.; Garcia, D. First report of Peronospora sp. on sweet basil (Ocimum basilicum) in Cuba. Plant Pathol. 2010, 59, 800. [Google Scholar] [CrossRef]
  84. Koroch, A.R.; Villani, T.S.; Pyne, R.M.; Simon, J.E. Rapid staining method to detect and identify downy mildew (Peronospora belbahrii) in basil. Appl. Plant Sci. 2013, 1, 1300032. [Google Scholar] [CrossRef]
  85. Shao, D.; Tian, M. A qPCR approach to quantify the growth of basil downy mildew pathogen Peronospora belbahrii during infection. Curr. Plant Biol. 2018, 15, 2–7. [Google Scholar] [CrossRef]
  86. Wyenandt, C.A.; Maimone, L.R.; Homa, K.; Madeiras, A.M.; Wick, R.L.; Simon, J.E. Detection of the downy mildew pathogen on seed of basil following field infection in Southern New Jersey. HortTechnology 2018, 28, 637–641. [Google Scholar] [CrossRef]
  87. Standish, J.R.; Raid, R.N.; Pigg, S.; Quesada-Ocampo, L.M. A diagnostic guide for basil downy mildew. Plant Health Prog. 2020, 21, 77–81. [Google Scholar] [CrossRef]
  88. Pyne, R.M.; Koroch, A.R.; Wyenandt, C.A.; Simon, J.E. A rapid screening approach to identify resistance to basil downy mildew (Peronospora belbahrii). HortScience 2014, 49, 1041–1045. [Google Scholar] [CrossRef]
  89. McGrath, M.T. Efficacy of conventional fungicides for downy mildew in field-grown sweet basil in the United States. Plant Dis. 2020, 104, 2967–2972. [Google Scholar] [CrossRef]
  90. Cohen, Y.; Vaknin, M.; Ben-Naim, Y.; Rubin, A.E. Light suppresses sporulation and epidemics of Peronospora belbahrii. PLoS ONE 2013, 8, e81282. [Google Scholar] [CrossRef]
  91. Cohen, Y.; Vaknin, M.; Ben-Naim, Y.; Rubin, A.E. Nocturnal fanning suppresses downy mildew epidemics in sweet basil. PLoS ONE 2016, 11, e0155330. [Google Scholar] [CrossRef]
  92. Tinivella, F.; Hirata, L.M.; Celan, M.A.; Wright, A.I.; Amein, T.; Schmitt, A.; Koch, E.; Garibaldi, A.; Gullino, M.L. Control of seed-borne pathogens on legumes by microbial and other alternative seed treatments. Eur. J. Plant Pathol. 2009, 123, 139–151. [Google Scholar] [CrossRef]
  93. Gilardi, G.; Pintore, I.; Demarchi, S.; Gullino, M.L.; Garibaldi, A. Seed dressing to control downy mildew of basil. Phytoparasitica 2015, 44, 531–539. [Google Scholar] [CrossRef]
  94. Lopez-Reyes, J.G.; Gilardi, G.; Garibaldi, A.; Gullino, M.L. In vivo evaluation of essential oils and biocontrol agents combined with heat treatments on basil cv Genovese Gigante seeds against Fusarium oxysporum f. sp. basilici. Phytoparasitica 2016, 44, 35–45. [Google Scholar] [CrossRef]
  95. Omer, C.; Nisan, Z.; Rav-David, D.; Elad, Y. Effects of agronomic practices on the severity of sweet basil downy mildew (Peronospora belbahrii). Plants 2021, 10, 907. [Google Scholar] [CrossRef] [PubMed]
  96. La Placa, L.; Cornali, S.; Bertinara, F.; Rossetti, A.; Reggiani, R.; Battilani, P. Cropping system support downy mildew control in basil in organic farming: A two-year open field experiment. J. Plant Pathol. 2025, 107, 167–179. [Google Scholar] [CrossRef]
  97. Elad, Y.; Kleinman, Z.; Nisan, Z.; Rav-David, D.; Yermiyahu, U. Effects of calcium, magnesium and potassium on sweet basil downy mildew (Peronospora belbahrii). Agronomy 2021, 11, 688. [Google Scholar] [CrossRef]
  98. Elad, Y.; Nisan, Z.; Kleinman, Z.; Rav-David, D.; Yermiyahu, U. Effects of microelements on downy mildew (Peronospora belbahrii) of sweet basil. Plants 2021, 10, 1793. [Google Scholar] [CrossRef] [PubMed]
  99. Rav David, D.; Yermiyahu, U.; Fogel, M.; Faingold, I.; Elad, Y. Plant nutrition for management of white mold in sweet basil. Phytoparasitica 2019, 47, 99–115. [Google Scholar] [CrossRef]
  100. Yermiyahu, U.; Israeli, L.; Rav David, D.; Faingold, I.; Elad, Y. Higher potassium concentration in shoots reduces gray mold in sweet basil. Phytopathology 2015, 105, 1059–1068. [Google Scholar] [CrossRef][Green Version]
  101. Wyenandt, C.A.; Simon, J.E.; McGrath, M.T.; Ward, D.L. Susceptibility of basil cultivars and breeding lines to downy mildew (Peronospora belbahrii). HortScience 2010, 45, 1416–1419. [Google Scholar] [CrossRef]
  102. Farahani-Kofoet, R.D.; Römer, P.; Grosch, R. Selecting basil genotypes with resistance against downy mildew. Sci. Hortic. 2014, 179, 22–28. [Google Scholar] [CrossRef]
  103. Naim, B.Y.; Falach, L.; Cohen, Y. Resistance against basil downy mildew in Ocimum species. Phytopathology 2015, 105, 778–785. [Google Scholar] [CrossRef] [PubMed]
  104. Homa, K.; Barney, W.P.; Ward, D.L.; Wyenandt, C.A.; Simon, J.E. Morphological characteristics and susceptibility of basil species and cultivars to Peronospora belbahrii. HortScience 2016, 51, 1389–1396. [Google Scholar] [CrossRef]
  105. Naim, B.Y.; Weitman, M. Joint action of Pb1 and Pb2 provides dominant complementary resistance against new races of Peronospora belbahrii (basil downy mildew). Phytopathology 2022, 112, 595–607. [Google Scholar] [CrossRef] [PubMed]
  106. Pyne, R.M.; Koroch, A.R.; Wyenandt, C.A.; Simon, J.E. Inheritance of resistance to downy mildew in sweet basil. J. Am. Soc. Hortic. Sci. 2015, 140, 396–403. [Google Scholar] [CrossRef]
  107. Pyne, R.M.; Honig, J.; Vaiciunas, J.; Bonos, S.; Wyenandt, A.; Simon, J.E. A first genetic map and downy mildew resistance QTL discovery for sweet basil (Ocimum basilicum). PLoS ONE 2017, 12, e0184319. [Google Scholar] [CrossRef]
  108. Zhang, X.; Low, Y.C.; Lawton, M.A.; Simon, J.E.; Di, R. CRISPR-editing of sweet basil (Ocimum basilicum L.) homoserine kinase gene for improved downy mildew disease resistance. Front. Genome Ed. 2021, 3, 629769. [Google Scholar] [CrossRef]
  109. Naim, B.Y.; Falach, L.; Cohen, Y. Transfer of downy mildew resistance from wild basil (Ocimum americanum) to sweet basil (O. basilicum). Phytopathology 2018, 108, 114–123. [Google Scholar] [CrossRef]
  110. Patel, J.S.; Wyenandt, C.A.; McGrath, M.T. Effective downy mildew management in basil using resistant varieties, environment modifications, and fungicides. Plant Health Prog. 2021, 22, 226–234. [Google Scholar] [CrossRef]
  111. Thines, M.; Telle, S.; Ploch, S.; Runge, F. Identity of the downy mildew pathogens of basil, coleus, and sage with implications for quarantine measures. Fungal Biol. 2009, 113, 532–540. [Google Scholar] [CrossRef] [PubMed]
  112. Thines, M.; Sharma, R.; Rodenburg, S.Y.; Gogleva, A.; Judelson, H.S.; Xia, X.; de Ridder, D. The genome of Peronospora belbahrii reveals high heterozygosity, a low number of canonical effectors and CT-rich promoter. Mol. Plant Microbe Interact. 2019, 33, 742–753. [Google Scholar] [CrossRef]
  113. Naim, B.Y.; Mattera, R.; Cohen, Y.; Wyenandt, A.C.; Simon, J.E. Predicting the resistance of basil entries to downy mildew based on their genetics, pathogen race, growth stage, and environmental conditions. Planta 2025, 262, 10. [Google Scholar] [CrossRef] [PubMed]
  114. Gullino, M.L.; Gilardi, G.; Garibaldi, A. Chemical control of downy mildew on lettuce and basil under greenhouse. Commun. Agric. Appl. Biol. Sci. 2009, 74, 933–940. [Google Scholar]
  115. Gilardi, G.; Demarchi, S.; Garibaldi, A.; Gullino, M.L. Management of downy mildew of sweet basil (Ocimum basilicum) caused by Peronospora belbahrii by means of resistance inducers, fungicides, biocontrol agents and natural products. Phytoparasitica 2013, 41, 59–72. [Google Scholar] [CrossRef]
  116. Homa, K.; Barney, W.P.; Ward, D.L.; Wyenandt, C.A.; Simon, J.E. Evaluation of fungicides for the control of Peronospora belbahrii on sweet basil in New Jersey. Plant Dis. 2014, 98, 1561–1566. [Google Scholar] [CrossRef]
  117. Margot, P.; Huggenberger, F.; Amrein, J.; Weiss, B. CGA 279202: A new broad-spectrum strobilurin fungicide. In Proceedings Brighlon Crop Proleclion Conference, Pests and Diseases; British CropProtection Council: Surrey, UK, 1998; pp. 375–382. [Google Scholar]
  118. Huggenberger, F.; Lamberth, C.; Iwanzik, W. Mandipropamid, a new fungicide against oomycete pathogens. In Proceedings of the BCPC International Congress, Glasgow, UK, 31 October–2 November 2005. [Google Scholar]
  119. Patel, J.S.; Costa de Novaes, M.I.; Zhang, S. Evaluation of the new compound oxathiapiprolin for control of downy mildew in basil. Plant Health Prog. 2015, 16, 165–172. [Google Scholar] [CrossRef]
  120. Patel, J.S.; Zhang, S.; de Novaes, M.I.C. Effect of plant age and acibenzolar-S-methyl on development of downy mildew of basil. HortScience 2014, 49, 1392–1396. [Google Scholar] [CrossRef]
  121. Pintore, I.; Gilardi, G.; Gullino, M.L.; Garibaldi, A. Detection of mefenoxam-resistant strains of Peronospora belbahrii, the causal agent of basil downy mildew, transmitted through infected seeds. Phytoparasitica 2016, 44, 563–569. [Google Scholar] [CrossRef]
  122. Bączek, K.; Kosakowska, O.; Gniewosz, M.; Gientka, I.; Węglarz, Z. Sweet basil (Ocimum basilicum L.) productivity and raw material quality from organic cultivation. Agronomy 2019, 9, 279. [Google Scholar] [CrossRef]
  123. Mersha, Z.; Zhang, S.; Raid, R.N. Evaluation of systemic acquired resistance inducers for control of downy mildew on basil. Crop Prot. 2012, 40, 83–90. [Google Scholar] [CrossRef]
  124. Guest, D.; Grant, B.R. The complex action of phosphonates as antifungal agents. Biol. Rev. 1991, 66, 159–187. [Google Scholar] [CrossRef]
  125. Mitchell, A.F.; Walters, D.R. Potassium phosphate induces systemic protection in barley to powdery mildew infection. Pest Manag. Sci. 2004, 60, 126–134. [Google Scholar] [CrossRef]
  126. McGrath, M.T.; LaMarsh, K.A. Evaluation of fungicides for managing downy mildew in basil, 2012. Plant Dis. Manag. Rep. 2013, 7, V015. [Google Scholar]
  127. Gullino, M.L.; Pugliese, M.; Garibaldi, A. Use of Silicon Amendments Against Foliar and Vascular Diseases of Vegetables Grown Soil-less. In Sustainable Crop Disease Management Using Natural Products; Ganesan, S., Vadivel, K., Jayaraman, J., Eds.; CRC Press: Boca Raton, FL, USA, 2015; pp. 293–306. [Google Scholar] [CrossRef]
  128. Paarlberg, A.; Babadoost, M. Evaluating effectiveness of selected compounds for control of downy mildew of basil in Momence, Illinois, 2021. Plant Dis. Manag. Rep. 2022, 16, V061. [Google Scholar] [CrossRef]
  129. Elad, Y.; Israeli, L.; Fogel, M.; Adler, U. Conditions influencing the development of sweet basil gray mold and cultural measures for disease management. Crop Prot. 2014, 64, 67–77. [Google Scholar] [CrossRef]
  130. McGrath, M.T. Efficacy of organic fungicides for downy mildew in field-grown sweet basil. Plant Dis. 2023, 107, 2467–2473. [Google Scholar] [CrossRef]
Agriculture 15 01999 g001
Figure 1. Open field basil crops affected by Peronospora belbahrii.
Figure 1. Open field basil crops affected by Peronospora belbahrii.
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Figure 2. Leaf spot and sporulation on basil caused by Peronospora belbahrii.
Figure 2. Leaf spot and sporulation on basil caused by Peronospora belbahrii.
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Figure 3. Branched sporangiophores and sporangia of Peronospora belbahrii.
Figure 3. Branched sporangiophores and sporangia of Peronospora belbahrii.
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Table 1. Reports of basil downy mildew in different countries throughout the world.
Table 1. Reports of basil downy mildew in different countries throughout the world.
Continent/Country/Region (Year of First Report)Reference
Africa
Benin (1998)[53]
Cameroon (2007)[55]
South Africa (2005)[56]
Tanzania (1960)[52]
Uganda (1933)[48]
Asia and Oceania
China:
- Beijing (2016)[57]
- Hainan (2014)[58]
Iran (2006)[59]
Israel (2011)[60]
Japan (2007)[61]
South Korea (2015)[62]
Taiwan (2009)[63]
New Zealand (2005)[64]
Europe
Austria (2005)[65]
Belgium (2004)[66]
Croatia (2012)[67]
Cyprus (2012)[68]
The Czech Republic (2012)[69,70]
France (2004)[71]
Germany (2005)[51]
Hungary (2003)[72]
Italy (2003)[73]
Malta (2005)[74]
Spain (2016)[75]
Switzerland (2001)[76]
The United Kingdom (2005)[77]
North America
Canada (2011):[78]
- British Columbia (2011)[79]
- Ontario (2011)[78]
- Quebec (2011)[79]
The United States:
- Florida (2007)
- Arkansas, California, Connecticut, Delaware, District of Columbia, Kansas, Massachusetts, New Jersey, New York, North Carolina, North Dakota (2008)
- Alabama, Illinois, Indiana, Louisiana, Maryland, Pennsylvania, South Carolina, Texas, Vermont, Wisconsin (2009)
- Hawaii, Kentucky, Michigan, Montana, Ohio, Virginia (2010)
- Alaska, Minnesota, Washington (2011)
- Colorado, Maine, Missouri, New Hampshire, Oregon, Rhode Island, West Virginia (2012)
- New Mexico, Tennessee (2013)
- Iowa, Nebraska (2014)		[80]
- Mississippi, Oklahoma (2016)[32]
Mexico (2009)[64]
Central and South America
Argentina (2008)[81]
Brazil (2017)[82]
Cuba (2009)[83]
Table 2. Resistance to downy mildew in commercial basil cultivars developed for use in open fields.
Table 2. Resistance to downy mildew in commercial basil cultivars developed for use in open fields.
Name of the CultivarOrigin/Seed CompanyDegree of ResistanceReferences
AmazelUniversity of Florida100%[3]
EleonoraEnza Zaden26 and 34% control[3]
Prospera PlusGenesis Seeds100%[3]
ProsperaGenesis Seeds60%[96]
Devotion, Obsession, Passion, ThunderstruckRutgers DMR46–99% control[3]
Table 3. Effect of foliar spraying with salt alone or after fungicides on downy mildew of cv. Italiano basil grown in a greenhouse and under artificial inoculation (From Gilardi et al. [2]).
Table 3. Effect of foliar spraying with salt alone or after fungicides on downy mildew of cv. Italiano basil grown in a greenhouse and under artificial inoculation (From Gilardi et al. [2]).
Fungicide
(No. of Applications) 1		Salt
(No. of Applications)		Interval Between
Sprays
(Days)		Total
No. Sprays		% of the Infected Leaf Area
Inoculated untreated control 2---28.8±3.5h 3E%
Pyraclostrobin + dimethomorph (1)Calcium oxide (4)351.8±0.5a93.9
Fluopicolide (1)Calcium oxide (4)355.7±1.1ab80.4
Mandipropamid (1)Calcium oxide (4)354.5±0.9ab84.3
Pyraclostrobin + dimethomorph (1)Calcium oxide (2)633.6±0.7ab87.6
Fluopicolide (1)Calcium oxide (2)6310.8±0.7b–f62.4
Mandipropamid (1)Calcium oxide (2)639.2±1.8a–d68.1
Pyraclostrobin + dimethomorph (1)Potassium phosphite (2)636.5±0.9ab77.5
Fluopicolide (1)Potassium phosphite (2)639.4±1.4b–e67.2
Mandipropamid (1)Potassium phosphite (2)637.9±2.0a–c72.7
Calcium oxide (5)357.5±1.4a–c73.9
Calcium oxide (3)6314.8±1.6c–g48.4
Potassium phosphite (3)6316.9±1.1e–g41.2
Copper sulphite (3)-6320.3±1.1g29.5
Pyraclostrobin + dimethomorph (1)--16.0±1.1ab79.2
Fluopicolide (1)--117.1±1.5fg40.4
Mandipropamid (1)--116.1±1.5d–g44.2
Pyraclostrobin + dimethomorph (1); fluopicolide (1); mandipropamid (1)-631.7±0.7a94.2
Non-inoculated untreated control---7.4±1.6a–c74.3
1 One fungicide spray followed by 2 or 4 applications of alternative product sprays at 3- or 6-day intervals. 2 One artificial inoculation 24 h after the first treatment with 1 × 105 sporangia/mL. 3 The data in each column followed by a different letter are significantly different according to Tukey’s HSD test (p < 0.05). Standard errors are reported.
Table 4. Efficacies of different treatments against downy mildew (caused by Peronospora belbarhii) on basil cv. Genovese, ‘Italiano Classico’ selection grown under artificial inoculation in a greenhouse (from Gilardi et al. [115]).
Table 4. Efficacies of different treatments against downy mildew (caused by Peronospora belbarhii) on basil cv. Genovese, ‘Italiano Classico’ selection grown under artificial inoculation in a greenhouse (from Gilardi et al. [115]).
Active IngredientCommercial ProductDosage (g a.i./100 L) 1Efficacy on the Day After the Last Treatment (DAT) in Three Trials
DAT15 (Trial 1)DAT13
(Trial 2)		DAT15 (Trial 3)
-Inoculated control 2--
Copper oxychlorideCupravit flow5078.442.142.1
Copper oxychloride + copper hydroxideAirone40 + 4089.177.277.2
Acibenzolar-S-methylBion197.689.989.9
Organic mineral fertilizer N:KKendal10.5 + 4545.647.247.2
Mineral fertilizer: Cu + Mn + ZnKendal TE46 + 1.5 + 1.590.671.171.1
Prohexadione-CaRegalis583.965.765.7
Thyme oil extractTyme oil10030.430.130.1
Bacillus subtilis QST713Serenade58.484.551.151.1
Glucohumate activator complex zGlucoinductor40039.244.744.7
Copper sulphate + copper gluconateLabimethyl9 + 6100.089.689.6
Copper hydroxide and terpenic alcoholsHeliocuivre6091.842.142.1
Copper sulfateCuproxat53.298.880.980.9
Mineral fertilizer P2O5 52%, K2O 42%Alexin130 + 10591.559.659.6
Metalaxyl-M + copper hydroxideRidomil Gold R7.5+ 120100.087.187.1
MandipropamidPergado11.7100.0100.0100.0
AzoxystrobinOrtiva18.6100.0100.0100.0
1 Two treatments were applied at 7-day intervals, except for metalaxyl-M + copper hydroxide, mandipropamid, and azoxystrobin, which were applied once on 14 October 2011. 2 One artificial inoculation, with 1 × 105 sporangia/mL, was applied 24 h after the first treatment.
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Pugliese, M.; Gilardi, G.; Garibaldi, A.; Gullino, M.L. Basil Downy Mildew (Peronospora belbahrii): A Major Threat to Ocimum basilicum L. Production. Agriculture 2025, 15, 1999. https://doi.org/10.3390/agriculture15191999

AMA Style

Pugliese M, Gilardi G, Garibaldi A, Gullino ML. Basil Downy Mildew (Peronospora belbahrii): A Major Threat to Ocimum basilicum L. Production. Agriculture. 2025; 15(19):1999. https://doi.org/10.3390/agriculture15191999

Chicago/Turabian Style

Pugliese, Massimo, Giovanna Gilardi, Angelo Garibaldi, and Maria Lodovica Gullino. 2025. "Basil Downy Mildew (Peronospora belbahrii): A Major Threat to Ocimum basilicum L. Production" Agriculture 15, no. 19: 1999. https://doi.org/10.3390/agriculture15191999

APA Style

Pugliese, M., Gilardi, G., Garibaldi, A., & Gullino, M. L. (2025). Basil Downy Mildew (Peronospora belbahrii): A Major Threat to Ocimum basilicum L. Production. Agriculture, 15(19), 1999. https://doi.org/10.3390/agriculture15191999

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