Control Of Mildew Research Articles

Survey of Spinach Downy Mildew Management Practices and Communication Network

California spinach growers struggle to manage downy mildew effectively. Management practices are available, but it is not known how growers perceive their relative efficacy. It is also not clear who growers contact for information on spinach downy mildew management. In this study, we conducted an online survey of people involved in spinach production in the United States, asking who they contact to discuss spinach downy mildew control, the frequency of that contact, and the perceived efficacy of potential management practices. Growers were the group that was the most frequently contacted about spinach downy mildew. We found that respondents perceived resistant cultivars and the use of synthetic fungicides to be the most effective, with much lower perceived efficacy for the practices of disking diseased fields, application of certified organic fungicides, and roguing diseased plants.

Powdery Mildew A Disease of Grapes And The Fungicides Mode of Action: A Review

Powdery mildew caused by Uncinula necator (Schw.) Burr. is one of the widespread fungal diseases of grapes that have caused economic losses through poor fruit set and low yield substantially. To decrease the inoculum potential, a disease management program must be undertaken early in the season which is imperative to reduce late-season disease problems. Because, without early control of the infection of powdery mildew, often lead to severe problem in the late season. Elemental sulfur was the foremost antifungal utilized for the control of powdery mildew which is still in use as an effective and cheap fungicide for vineyards. Sterolbiosynthesis inhibitors (SI), also called SI fungicides, are the latest products to control powdery mildew effectively. For efficient use of fungicides with no or less resistance to the pathogen, it is appropriate to spray fungicides having different mechanisms of action which are specific in function, and for more efficacy, use a mixture of such fungicides that have no harmful impact on plant growth and environment. So, for effective control of powdery mildew, a protective spray of fungicide before bloom and a subsequent spray of systemic fungicides at the time of berry formation ensure healthy and higher grapes yield. This paper reviewed the powdery mildew infection in grapevines and its effect on yield losses with details of fungicides’ mechanism of action and newly developed fungicides having broad spectrum activities.

Effectiveness of the Field Application of UV-C for Cucumber Downy Mildew Control

There is growing interest in the application of ultraviolet (UV-C) energy to control crop pathogens. In the present study, the efficacies of UV-C treatments for controlling cucumber downy mildew (Pseudoperonospora cubensis) were investigated on a commercial farm in eastern Massachusetts, USA. Controlled doses of UV-C, delivered by a tractor-mounted array of sources, between 120 and 480 J·m-2 were applied and compared to conventional fungicide treatments as well as to untreated controls, for each of two consecutive years (2020 and 2021). Visual assessments of foliar disease severity in the trial plots were made several times from planting through the end of productive life. In contrast to the successful control of powdery mildew, the UV-C treatments for controlling cucumber downy mildew were not as successful as conventional fungicides. None of the UV-C treatments affected the overall progression rate of downy mildew once the disease became apparent, although disease onset was delayed slightly compared to untreated controls. This delay may have been due to UV-C induced resistance to infection by the host. Unlike powdery mildews, downy mildew spores from P. cubensis are darkly pigmented, possibly decreasing the efficacy of the UV-C treatments for controlling the disease. DM spores may also be only susceptible to UV exposure prior to encysting in the leaves of the host, thereby perhaps limiting the window of opportunity when UV-C treatments can be effective. Although not the primary focus of this study, the use of reflective mulch appeared to delay disease onset relative to black mulch in fields with significant sunlight exposure, perhaps due to lowering plant stress by maintaining a lower soil temperature.

Wetting and deposition behaviors of pesticide droplets with different dilution ratios on wheat leaves infected by pathogens

The pesticide formulations should be diluted to different concentrations according to selected application methods. The structure and properties of crop leaf surfaces can undergo severe changes after infestation with pests or diseases. Previous studies have mostly focused on the interfacial behaviors of pesticide droplets on healthy plant leaves. Here, we prepared 25 % pyraclostrobin microemulsion and diluted it according to different dilution ratios corresponding to low volume and conventional volume spray methods. The dynamic wetting and deposition behaviors of pesticide solution on wheat leaves infected with powdery mildew were investigated. The surface structure and properties of wheat leaves covered by the fungus Blumeria graminis will be changed. Conidia produce more non-polar components. The droplets with low dilution were more likely to deposit and reach the Wenzel state on wheat powdery mildew leaves. However, the droplets with high dilution were difficult to wet and easy to break and rebound from leaf surfaces. This research guides the control of wheat powdery mildew with pesticides under different application methods and the interface interaction between pesticide droplets and hydrophobic leaf surfaces infected by pathogens.

Mitigation of Powdery Mildew Disease by Integrating Biocontrol Agents and Shikimic Acid with Modulation of Antioxidant Defense System, Anatomical Characterization, and Improvement of Squash Plant Productivity

Squash (Cucurbita pepo L.) is a globally important vegetable, the production of which is severely constrained by powdery mildew caused by Podosphaera xanthii. In this study, we examined the effects of Trichoderma asperellum (MW965676), Streptomyces rochei (MN700192), and a mixture of the two foliar sprays with or without shikimic acid seed priming treatment on powdery mildew severity, plant growth, and total yield during the 2020–2021 and 2021–2022 growing seasons. We also studied their immune eliciting properties by examining their enzymatic, phenolic, and hormonal functions. The combination of Trichoderma asperellum, Streptomyces rochei, and shikimic acid triggered plant defense responses, which elicited enzyme activities such as peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT), phenolic compound accumulation, and increased salicylic acid (SA) and jasmonic acid (JA) content. This approach yielded high-quality results in the control of powdery mildew during the two growing seasons under greenhouse conditions. Additionally, relatively large statistical differences in plant growth, total yield, mineral components, and physiological traits were observed. A GC–MS analysis of Trichoderma asperellum (MW965676) showed hemin cation as a major component, while Streptomyces rochei (MN700192) contained 2,4-di-tert-butyl phenol and the hexadecenoic acid methyl ester. With respect to the morphological changes induced by powdery mildew and the treatments, plants treated with a mixture of Trichoderma asperellum, Streptomyces rochei and shikimic acid showed an improvement in the thickness of the midvein, increased dimensions of the main midvein bundle, a larger number of xylem rows in the main midvein bundle, greater mean diameters of vessels and of parenchyma cells in the ground tissues, as well as increased thickness of the upper and lower epidermis, lamina, palisade tissue and spongy tissue. This extensive, new study is the first step toward a more profound understanding of the use of Trichoderma asperellum and Streptomyces rochei with shikimic acid-primed seeds as a potential alternative technique for attenuating powdery mildew infection in squash.

Efficacy of Organic Fungicides Against Hemp Powdery Mildew Caused by Golovinomyces ambrosiae in a Greenhouse in Tennessee.

Powdery mildew is a common disease of hemp in greenhouses in Tennessee. Fungicide efficacy data can support the use or approval of new fungicides. Therefore, two greenhouse experiments were conducted to assess the efficacy of nine commercial fungicides against powdery mildew. 'BaOx2' or 'Sweetened' hemp cultivars, which are susceptible to powdery mildew, were inoculated with a conidial suspension 1 day before or 1 day after the first fungicide application. Two additional fungicide applications were made at 7-day intervals by thoroughly spraying the plants using a hand-held sprayer. Control plants were sprayed with water only. Weekly disease incidence and severity ratings were done three times. Disease index and the area under the disease progress curve were calculated. All the fungicides significantly reduced powdery mildew symptoms. Compared with the control plants, disease reductions ranged from 76 to 100%. Bonide sulfur, Luna Experience, and MilStop exhibited "excellent" efficacy, reducing disease symptoms by 96 to 100%. Cinnerate, Exile, Regalia, and Sil-Matrix exhibited "very good" efficacy, reducing disease symptoms by 86 to 95%. Defguard and Stargus exhibited "good" efficacy, reducing disease symptoms by 76 to 85%. Koch's postulates were performed with the PM isolate used in this study. The isolate recovered following inoculation was found to be identical to the original isolate used in the experiments. The isolate was identified as Golovinomyces ambrosiae based on ITS, IGS, and β-tubulin sequencing and phylogenetic analysis with nucleotide sequences from closely related species. These findings provide useful information for the control of hemp powdery mildew and further research.

Biological Control of Downy Mildew and Yield Enhancement of Cucumber Plants by Trichoderma harzianum and Bacillus subtilis (Ehrenberg) under Greenhouse Conditions

The downy mildew disease of cucurbits is considered the most economically damaging disease of Cucurbitaceae worldwide. The causal agent, Pseudoperonospora cubensis (Berkeley & Curtis), may cause complete crop losses of cucurbits. Few commercial cucurbit cultivars are resistant to this disease. Commercially, P. cubensis is controlled primarily with synthetic fungicides that inhibit or eliminate the pathogen. Several biological agents have also been identified that provide some level of control. In our study, foliar applications of three strains of Trichoderma harzianum and two native strains of Bacillus subtilis were evaluated for the control of the disease on cucumber plants grown under commercial greenhouse conditions. The study was conducted using a completely randomized design with six individual treatments during two production cycles: fall 2015 and spring 2016. The response variables included disease incidence and severity, plant height, total yield, fruit quality, and weight. B. subtilis provided the best control over the incidence and severity of the disease in both production cycles. Interestingly, while T. harzianum was less effective at controlling the disease, it enhanced plant growth and productivity, and produced a higher number of better-quality fruits per plot. This increased yield with higher quality fruits may result in higher profit for the growers.

Prediction and determination of mildew grade in grain storage based on FOA-SVM algorithm

AbstractGrain mildew is a significant hazard that causes food loss and poses a serious threat to human health when severe. Therefore, effective prediction and determination of mildew grade is essential for the prevention and control of mildew and global food security. In the present study, a model for predicting and determining the mildew grade of rice was constructed using logistic regression, back propagation neural network and GS-SVM (a grid search-based support vector machine algorithm) based on laboratory culture data and actual data from a granary, respectively. The results show that the GS-SVM model has a better prediction effect, but the model cannot automatically adjust the parameters and is more subjective, and the accuracy may decrease when the data set changes. Therefore, this paper establishes a new model for a support vector machine based on a fruit fly optimization algorithm (FOA-SVM), which can achieve automatic parameter search and automatically adjust its parameters to find the best result when the data set changes, with a strong ability of self-adjustment of parameters. In addition, the FOA-SVM converges quickly and the model is stable. The results of this study provide a technical method for early identification of mildew grade during grain storage, which is beneficial for the prevention and control of rice mildew during grain storage.

Climate change increases the suitable area and suitability degree of rubber tree powdery mildew in China

Rubber tree powdery mildew is one of the most important diseases restricting the development of the natural rubber industry and the improvement of economic efficiency of rubber production. Climate change has seriously influenced the distribution and transmission of rubber tree powdery mildew. However, the impacts of future climate change on the suitable area and suitability degree of rubber tree powdery mildew have been rarely investigated. Based on environmental and disaster data of rubber tree powdery mildew in the baseline (1970–2000) and future climate change scenarios (2021–2040, 2041–2060, 2061–2080, and 2081–2100), Maximum Entropy Models (MaxEnt) model was used to simulate the impacts of future climate change on the distribution of suitable area and the suitability degree of rubber tree powdery mildew in China. The results showed that the MaxEnt model could effectively simulate the historical distribution and suitability degree of rubber tree powdery mildew. The top two major environmental variables were mean temperature of driest quarter and temperature seasonality considering their contribution rates of 44.2% and 24.61%, respectively. Currently, the suitable areas of the rubber tree powdery mildew were mainly concentrated in central and southern Hainan Island, southern Yunnan province, southern Guangxi province, southwestern Guangdong province, and southern Fujian province. Compared with the baseline, the suitable area of rubber tree powdery mildew would enlarge by 0.24%, 0.59%, 0.78%, and 3.25% respectively under 2021–2040, 2041–2060, 2061–2080, and 2081–2100 in China. The suitability degree of rubber tree powdery mildew would increase under future climate change scenarios in China with most significant increase in Hainan and Yunnan rubber planting areas. The key areas for rubber tree powdery mildew prevention and control would concentrate in the southern Yunnan province and the central Hainan Island. The study results could provide an important reference for ensuring the safe production of rubber tree and reducing the use and residue of agricultural chemicals and environmental impacts. • Temperature mainly determines the distribution of rubber tree powdery mildew. • Climate change enlarges the suitable area of rubber tree powdery mildew in China. • Climate change increases suitability degree of rubber tree powdery mildew in China.

Biocontrol action of Trichothecium roseum against the wheat powdery mildew fungus Blumeria graminis f. sp. tritici

Trichothecium roseum is known to be a mycoparasite and inhibit phytopathogenic fungi. However, so far, only scarce information is available on the impacts of T. roseum on powdery mildews. Based on the morphological and molecular analysis, we identified T. roseum as a mycoparasite on colonies of the wheat powdery mildew fungus (Blumeria graminis f. sp. tritici, Bgt, recently clarified as B. graminis s. str.) and then showed that T. roseum was capable of efficiently impairing colony formation and conidial distribution of Bgt. After inoculation of T. roseum conidia on Bgt colonies, the biomasses of Bgt significantly decreased 1.46, 1.64, 7.55, and 10.49 times at 2, 4, 6, and 8 dpi, respectively. Thus, T. roseum, acting as a potential biological agent, impeded the developments of Bgt, making it a viable alternative for wheat powdery mildew control. Utilizing the Agrobacterium tumefaciens-mediated transformation (ATMT) system, a T. roseum strain that constitutively expressed green fluorescent protein was produced to improve the visualization of the T. roseum-Bgt interaction and showed direct hyphae interaction of T. roseum with Bgt structures during parasitic processes. These findings indicate that ATMT is a potent and efficient method for transforming T. roseum. Nevertheless, our results suggest that T. roseum is an antagonistic parasite of the wheat powdery mildew fungus, and hence, can be considered for phytopathogen management.

Electrostatic Spore-Trapping Techniques for Managing Airborne Conidia Dispersed by the Powdery Mildew Pathogen

This review examines the progress of electrostatic spore-trapping research and the potential for the practical application of electrostatic apparatuses in powdery mildew control. These apparatuses produce an electric field by charging an insulated conductor wire (ICW). Airborne pathogen spores are subjected to an attractive force in the electric field and are drawn to the charged ICW as a result of dielectrophoretic movement. The strength of the attractive force is commensurate with the field strength (determined by the magnitude of the voltage applied to the ICW). Single-charged monopolar electric field screens (SM screens) are constructed by arraying negatively charged cylindrical ICWs in parallel at a specific interval. The connected electric fields of these ICWs form a gap-free air-shielding barrier. Wind-dispersed spores are precipitated by this barrier to create spore-free air. Oppositely charged SM screens have been combined to develop double-charged dipolar electric field screens, which generate a stronger spore attraction force under lower voltage application. Thus, electric field screens represent a promising physical method for creating spore-free spaces in cropping facilities, where plants can be cultivated without risk of infection by airborne fungal pathogens.

Combining melon varieties with chemical fungicides for integrated powdery mildew control in Tunisia

Combining melon varieties with chemical fungicides for integrated powdery mildew control in Tunisia

Anatomic and genetic factors associated with the susceptibility of grapevine cultivars to Plasmopara viticola clade aestivalis and clade riparia

The susceptibility of commonly grown grapevine cultivars in the province of Quebec to Plasmopara viticola (Berk. & M.A. Curtis) Berl. & De Toni clades riparia and aestivalis was compared. The relationship between anatomic (density and size of stomata and type of leaf hairs) and genetic composition (percentages of Vitis vinifera L., Vitis riparia Michx. and Vitis aestivalis Michx.) factors of the grapevine cultivars and their susceptibility to the two clades was investigated. The grapevine cultivars were classified according to their susceptibility to each clade. The aggressiveness of the clade riparia was positively correlated with stomata size and negatively correlated with type of leaf hairs. However, the aggressiveness of clade aestivalis was positively correlated with stomata size and density, estimated percentage of V. vinifera ancestry, and the published downy mildew susceptibility of grapevine cultivars; and negatively correlated with estimated percentage of V. riparia ancestry. Furthermore, the grapevine cultivar classification showed that, for P. viticola clade riparia, 44.4%, 44.4%, and 11.1% of the grapevine cultivars were classified as minimally susceptible, moderately susceptible, and highly susceptible, respectively. Alternatively, for P. viticola clade aestivalis, 11.1%, 22.2%, and 66.7% of the grapevine cultivars were classified as minimally susceptible, moderately susceptible, and highly susceptible, respectively. Although some grapevine cultivars fell in the same susceptibility groups for both clades, 78% of grapevine cultivars were classified in different susceptibility groups. The findings of this study provide new information on grapevine and P. viticola interactions, and highlight the importance of knowing which clade of P. viticola is present so that downy mildew control measures can be adapted accordingly.

Comparison of Ion Chromatography Conductivity Detection (IC-CD) and Ion Chromatography Inductively Coupled Plasma Mass Spectrometry (IC-ICP-MS) for the Determination of Phosphonic Acid in Grapevine Plant Parts, Wine, and Soil.

Potassium dihydrogen phosphonate had been allowed as a plant strengthener in organic viticulture in the European Union only until 2013, supporting the control of grapevine downy mildew. Therefore, low or nondetectable levels are a prerequisite for marketing of organic wines and, consequently, validated analytical methods are of major interest. Herein, two methods based on ion chromatography conductivity detection (IC-CD) or ion chromatography inductively coupled plasma mass spectrometry (IC-ICP-MS) for the determination of phosphonic acid (H3PO3) from 14 different plant matrices of Vitis vinifera L., wine, and soil were developed, validated, and compared. Extraction recoveries ranged from 95.1 to 99.3%. Limits of quantification (LOQ) ranged in liquid and solid samples from 3.8 to 16.8 μg/kg and 0.08 to 2.41 mg/kg for ICP-MS detection and from 39.9 to 593.7 μg/kg and 3.51 to 58.7 mg/kg for CD, respectively. Data on a current anonymized selection of 100 conventionally and 30 organically produced wines are briefly presented to demonstrate the suitability of the method.

Hyperparasitism on Plasmopara viticola by Simplicillium lanosoniveum

A previously unknown association between Plasmopara viticola, the causal pathogen of grape downy mildew, and the mycoparasite strain F2 is described in this paper. F2 could be consistently isolated from the mildew of diseased spots on grape leaves of Kyoho ( Vitis labrusca × V. vinifera cv. Kyoho) infected with P. viticola but not from the surfaces of healthy grape leaves or within lesions of other diseases. It was observed that strain F2 was capable of coiling around sporangiophores and sporangia of P. viticola under a microscope, causing hyphae deformation, decreasing the pathogen growth, and reducing the number of sporangia. This fungal strain was identified as Simplicillium lanosoniveum on the basis of morphological characterizations and 28S rDNA sequencing. To our knowledge, this is the first report of S. lanosoniveum with hyperparasitic characteristics on P. viticola, and the hyperparasite has potential application in the control of grape downy mildew. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

A pH‐ and redox‐stimulated responsive hollow mesoporous silica for triggered delivery of fungicides to control downy mildew of Luffa cylindrica

AbstractBACKGROUNDDowny mildew, a devastating disease of cucurbitaceous crops caused by Pseudoperonospora cubensis. Although a variety of fungicides are used to control downy mildew, choosing an effective product can be challenging. Environmental stimulus‐responsive pesticide delivery systems have great potential to improve the effectiveness of disease and pest control and reduce the impact on environmentally beneficial organisms.RESULTSIn this work, a disulfide bond (SS)‐modified and chitosan oligosaccharide (COS)‐capped hollow mesoporous silica (HMS) pesticide delivery system was synthesized using a hard template method for the control of downy mildew in cucurbit crops. The synthesized nanoparticles were loaded with dimethomorph (DMM), denoted as DMM@HMS‐SS‐COS, and the developmental toxicity of these nanoparticles to zebrafish embryos were evaluated. The results showed that the prepared DMM@HMS‐SS‐COS exhibited excellent dual response properties to pH and glutathione (GSH), with an encapsulation rate of up to 24.36%. DMM@HMS‐SS‐COS has good ultraviolet (UV) radiation stability and adhesion properties. Compared with dimethomorph suspension concentrate (SC), DMM@HMS‐SS‐COS was more effective against downy mildew for up to 21 days. Toxicity tests showed that DMM@HMS‐SS‐COS significantly reduced the effect of DMM on the hatching rate and survival rate of zebrafish embryos.CONCLUSIONSThis work not only demonstrates that DMM@HMS‐SS‐COS could be used as a nanodelivery system for intelligent control of downy mildew but also emphasizes the necessity of increasing the acute toxicity of nanoformulations to non‐target organisms in environmental risk assessment. © 2022 Society of Chemical Industry.

A Comparative Analysis of Microbe-Based Technologies Developed at ICAR-NBAIM Against Erysiphe necator Causing Powdery Mildew Disease in Grapes (Vitis vinifera L.).

Globally, Erysiphe necator causing powdery mildew disease in grapevines (Vitis vinifera L.) is the second most important endemic disease, causing huge economic losses every year. At present, the management of powdery mildew in grapes is largely dependent upon the use of chemical fungicides. Grapes are being considered as one of the high pesticide-demanding crops. Looking at the residual impact of toxic chemical pesticides on the environment, animal, and human health, microbe-based strategies for control of powdery mildew is an emerging technique. It offers an environment-friendly, residue-free, and effective yet safer approach to control powdery mildew disease in grapes. The mode of action is relatively diverse as well as specific to different pathosystems. Hence, the aim of this study was to evaluate the microbe-based technologies, i.e., Eco-pesticide®, Bio-Pulse®, and Bio-Care 24® developed at the Plant-Microbe Interaction and Rhizosphere Biology Lab, ICAR-NBAIM, Kushmaur, against grape powdery mildew and to integrate these technologies with a safer fungicide (sulfur) to achieve better disease control under organic systems of viticulture. The experiments were conducted at four different locations, namely, the vineyards of ICAR-NRCG, Rajya Draksha Bagayatdar Sangh (MRDBS), and two farmers' fields at Narayangaon and Junnar in the Pune district of Maharashtra. A significantly lower percent disease index (PDI) was recorded on the leaves of grape plants treated with Eco-Pesticide®/sulfur (22.37) followed by Bio-Pulse®/sulfur (22.62) and Bio-Care 24®/sulfur (24.62) at NRCG. A similar trend was observed with the lowest PDI on bunches of Eco-pesticide®/sulfur-treated plants (24.71) followed by Bio-Pulse®/sulfur (24.94) and Bio-Care®/sulfur (26.77). The application of microbial inoculants singly or in combination with sulfur has a significant positive impact on the qualitative parameters such as pH, total soluble solids (TSS), acidity, berry diameter, and berry length of the grapes at different locations. Among all the treatments, the Bio-Pulse®/sulfur treatment showed the highest yield per vine (15.02 kg), which was on par with the treatment Eco-Pesticide®/sulfur (14.94). When compared with the yield obtained from the untreated control, 2.5 to 3 times more yield was recorded in the plants treated with either of the biopesticides used in combination with sulfur. Even in the case of individual inoculation, the yield per vine was approximately two times higher than the untreated control and water-treated plants across the test locations. Results suggested that microbial technologies not only protect grapevines from powdery mildew but also enhance the quality parameters with increased yield across the test locations.

Mining of Wheat Pm2 Alleles for Goal-Oriented Marker-Assisted Breeding.

Powdery mildew of wheat, caused by Blumeria graminis f. sp. tritici (Bgt), is a devastating disease that seriously reduces yield and quality worldwide. Utilization of plant resistance genes is an attractive and effective strategy for controlling this disease. Among the reported powdery mildew (Pm) resistance genes, Pm2 exhibits a diverse resistance spectrum among its multiple alleles. It has been widely used in China for resistance breeding for powdery mildew. To mine more Pm2 alleles and clarify their distribution, we screened 33 wheat cultivars/breeding lines carrying Pm2 alleles from 641 wheat genotypes using diagnostic and Pm2-linked markers. To further investigate the relationships within the Pm2 alleles, we compared their resistance spectra, polymorphism of marker alleles and gene sequences, and found that they have identical marker alleles and gene sequences but diverse resistance spectra. In addition, the diagnostic kompetitive allele-specific PCR (KASP) marker, YTU-KASP-Pm2, was developed and was shown to detect all the Pm2 alleles in the different genetic backgrounds. These findings provide valuable information for the distribution and rational use of Pm2 alleles, push forward their marker-assisted breeding (MAS), and hence improve the control of wheat powdery mildew.

Kaolin particle film limits grapevine downy mildew epidemic under open‐field conditions and stimulates the plant defence response

Background and Aims Grapevine downy mildew, the most destructive grapevine disease caused by Plasmopara viticola, requires more environmentally friendly control measures. A chemically inert kaolin particle film (KPF) was tested for the control of downy mildew. Methods and Results Grapevines were pretreated with KPF before P. viticola infection under field conditions, then an epidemic was monitored for 2 years (2020 and 2021). A 6% KPF pretreatment significantly delayed the epidemic onset by 1–2 weeks and decreased the disease index by 30% compared to the untreated vines. The concentration of hydrogen peroxide and malondialdehyde in leaves was reduced by the KPF treatment, indicating mitigation of the oxidative damage caused by P. viticola infection. The protective effect of the application of KPF may be due to the increased activity of antioxidant enzymes and antioxidant metabolites. The activity of disease resistance enzymes and the expression of related genes were also increased by KPF treatment. Conclusions Kaolin particle film reduced grapevine downy mildew and reinforced the defence response of grapevines cultivated in the field. Significance of the Study The positive effect of KPF against downy mildew for grapevines in the field indicated that there is potential to develop KPF for the control of downy mildew.

Evaluation of plant protection efficacy in field conditions and side effects of Lysobacter capsici AZ78, a biocontrol agent of Plasmopara viticola

ABSTRACT Downy mildew, caused by Plasmopara viticola, is a highly significant grapevine disease causing severe yield losses and affecting wine quality. Disease control mainly relies on use of copper and synthetic fungicides. Today there is a growing interest in developing microbial biopesticides for downy mildew control in integrated and organic viticulture. Here, the bacterial biocontrol agent Lysobacter capsici AZ78 (AZ78) was tested following a holistic approach including in planta efficacy test (large-scale trial) combined with bioassays aiming to assess potential adverse effects on non-target organisms: beneficial arthropods (Aphidius rhopalosiphi and Typhlodromus pyri), the crustacean Daphnia magna, the algae Selenastrum capricornutum and soil organisms [earthworm Eisenia (Ei.) fetida and worm Enchytraeid (En.) albidus]. Moreover, side effects of AZ78 treatments on grape quality and wine-making process were assessed. The results showed that AZ78 was equally effective to reference fungicide (Kocide®2000) in controlling downy mildew on leaves and bunches. AZ78 had no significant effect on the mortality of the indicator arthropod species at a Limit test Rate, which was equal to four times the recommended field rate. Additionally, no significant effects (mortality, growth rate or reproduction) were observed on D. magna, Ei. albidus, En. fetida and S. capricornutum, indicating AZ78 low toxicity on non-target organisms. Likewise, the yeast population dynamics in fermenting musts was not affected, without compromising the fermentation processes and wine quality. Overall, this study provides new insights into the characterisation of the biocontrol agent AZ78 showing that this bacterium has the potential to be further developed as a commercial biopesticide.