Bunch Rot Of Grapes Research Articles

Reassessing the Etiology of Aspergillus Vine Canker and Summer Bunch Rot of Table Grapes in California.

Fungal taxonomy is in constant flux, and the advent of reliable DNA barcodes has enabled the enhancement of plant pathogen identification accuracy. In California, Aspergillus vine canker (AVC) and summer bunch rot (SBR) are economically important diseases that affect the wood and fruit of grapevines, respectively, and their causal agents are primarily species of black aspergilli (Aspergillus section Nigri). During the last decade, the taxonomy of this fungal group has been rearranged several times using morphological, physiological, and genetic analyses, which resulted in the incorporation of multiple cryptic species that are difficult to distinguish. Therefore, in this study, we aimed to reassess the etiology of AVC and SBR using a combination of morphological observations with phylogenetic reconstructions based on nucleotide sequences of the calmodulin (CaM) gene. Results revealed that the isolates causing AVC from recent isolations corresponded to A. tubingensis, whereas the isolates obtained from initial surveys when the disease was discovered were confirmed as A. niger and A. carbonarius. Similarly, the isolates obtained from table grapes with SBR symptoms and from spore traps placed in those vineyards were identified primarily as A. tubingensis, followed by A. niger and A. carbonarius. Notably, the A. niger isolates formed a subclade with strains previously known as A. welwitschiae, which is a species that was recently synonymized with A. niger. Overall, the most prevalent species was A. tubingensis, which was associated with both AVC and SBR, and representative isolates recovered from AVC-symptomatic wood, berries SBR symptoms, and spore traps were equally pathogenic in healthy wood and berries of 'Red Globe' grapevines. This study also constitutes the first report of A. tubingensis causing AVC and SBR of grapes in California and in the United States.

A Review of Cultural Practices for Botrytis Bunch Rot Management in New Zealand Vineyards.

Botrytis bunch rot of grapes (BBR) causes substantial crop and wine quality issues globally. Past and present foundations for BBR control are based upon synthetic fungicides and varying forms of canopy management. Many authors regard the continued dependence on fungicides as unsustainable and have urged greater deployment of cultural, biological and nutritional strategies. However, in contrast to organic wine production, the uptake of alternative strategies in conventional vineyards has been slow based on cost and perceived reliability issues. This review summarises research from many different wine growing regions in New Zealand with the aim of demonstrating how traditional and newly developed cultural control practices have cost-effectively reduced BBR. In addition to reviewing traditional cultural practices (e.g., leaf removal), mechanical tools are described that remove floral trash and mechanically shake the vines. Multi-omics has improved our knowledge of the underlying changes to grape berries after mechanical shaking. Exogenous applications of calcium may correct calcium deficiencies in the berry skin and reduce BBR but the outcome varies between cultivar and regions. Nitrogen aids in grapevine defence against BBR but remains a complex and difficult nutrient to manage. The sustainable growth of organics and The European Green Deal will stimulate researchers to evaluate new combinations of non-chemical BBR strategies in the next decade.

Predictive Analysis and Wine-Grapes Disease Risk Assessment Based on Atmospheric Parameters and Precision Agriculture Platform

In the precision viticulture domain, data recorded by monitoring devices are large-scale processed to improve solutions for grapes’ quality and global production and to offer various recommendations to achieve these goals. Soil-related parameters (soil moisture, structure, etc.) and atmospheric parameters (precipitation, cumulative amount of heat) may facilitate crop diseases occurrence; thus, following predictive analysis, their estimation in vineyards can offer an early-stage warning for farmers and, therefore, suggestions for their prevention and treatment are of particular importance. Using remote sensing devices (e.g., satellites, unmanned vehicles) and proximal sensing methods (e.g., wireless sensor networks (WSNs)), we developed an efficient precision agriculture telemetry platform to provide reliable assessments of atmospheric phenomena periodicity and crop diseases estimation in a vineyard near Bucharest, Romania. The novelty of the materials and methods of this work relies on providing comprehensive preliminary references about monitored parameters to enable efficient, sustainable agriculture. Comparative analyses for two consecutive years illustrate an excellent correlation between cumulative and daily heat, precipitation quantity, and daily evapotranspiration (ET). In addition, the platform proved viable for wine-grapes disease estimation (powdery mildew, grape bunch rot, and grape downy mildew) and treatment recommendations based on the elaborated phenological calendar. Our results, together with continuous monitoring for the upcoming years, may be used as a reference to perform productive, sustainable smart agriculture in terms of yield and crop quality in Romania. In the Conclusion section, we show that farmers and personnel from cooperatives can use this information to make assessments based on the correlation of the available data to avoid critical damage to the wine-grape.

Antifungal activity of non-conventional yeasts against Botrytis cinerea and non-Botrytis grape bunch rot fungi.

Grapes harbour a plethora of non-conventional yeast species. Over the past two decades, several of the species have been extensively characterised and their contribution to wine quality is better understood. Beyond fermentation, some of the species have been investigated for their potential as alternative biological tools to reduce grape and wine spoilage. However, such studies remain limited to a few genera. This work aimed to evaluate the antagonistic activity of grape must-derived non-conventional yeasts against Botrytis cinerea and non-Botrytis bunch-rotting moulds and to further elucidate mechanisms conferring antifungal activity. A total of 31 yeast strains representing 21 species were screened on different agar media using a dual culture technique and liquid mixed cultures, respectively. Pichia kudriavzevii was the most potent with a minimum inhibitory concentration of 102 cells/mL against B. cinerea but it had a narrow activity spectrum. Twelve of the yeast strains displayed broad antagonistic activity, inhibiting three strains of B. cinerea (B05. 10, IWBT FF1 and IWBT FF2), a strain of Aspergillus niger and Alternaria alternata. Production of chitinases and glucanases in the presence of B. cinerea was a common feature in most of the antagonists. Volatile and non-volatile compounds produced by antagonistic yeast strains in the presence of B. cinerea were analysed and identified using gas and liquid chromatography mass spectrometry, respectively. The volatile compounds identified belonged mainly to higher alcohols, esters, organosulfur compounds and monoterpenes while the non-volatile compounds were cyclic peptides and diketopiperazine. To our knowledge, this is the first report to demonstrate inhibitory effect of the non-volatile compounds produced by various yeast species.

First report of Rhizopus stolonifer causing Rhizopus bunch rot on grapes in Pakistan

During June 2016, a postharvest survey of table grapes was carried out in the main fruit markets of Attock (33°46'07.9"N 72°21'43.0"E) and Jehlum (32°56'22.3"N 73°43'31.4"E) districts of Punjab Province. At the time of sampling, two cultivars (King’s Ruby and Perlette) were sampled at five different locations of both districts. Disease incidence % of bunches averaged 3 to 4 %. Some infected fruit appeared water-soaked, light brown and covered by fluffy mycelium consisting of erect sporangiophores with black sporangia on the top (Figure 1). Symptomatic tissue pieces were surface-sterilized with 0.1% NaOCl for 30 sec, rinsed three times with sterile distilled water, dried on filter paper for 45 sec and incubated on potato dextrose agar (PDA) at 25°C. After 1 day, mycelium on PDA was transferred to a fresh PDA plate and incubated at 25°C with a 12-h photoperiod. Within 3 days, white to yellow colonies with black aerial sporangia were formed (Figure 2). A total of 64 isolates were examined morphologically. Sporangiophores were erect, light brown and 623 to 3800 µm long. One to three rhizoids were observed opposite to each sporangiophore. Sporangia were black, globose to sub-globose, 91 to 124 μm in diameter. Columellae were conical to cylindrical and 86 to 187 μm long × 72 to 205 μm wide. Sporangiospores were hyaline to light dark grey, globose, ellipsoidal in shape and 6.8 to 12.4 × 3.6 to 12.5 μm (Figure 3). These features were identical to the description of Rhizopus stolonifer (Ehrenb.) Vuill (Liou et al., 2007). For molecular identification, the ITS1-5.8S-ITS2 region of two representative isolates (Rizo 05 and Rizo 07) was amplified with primers ITS1/ITS4 (White et al., 1990). Sequence comparison of two isolates Rizo05 and Rizo 07 (Accession no. MH348205 and MH356272) revealed 100% identity with previously reported isolates of Rhizopus stolonifer (Accession no. MG865992, KU729185, HM051076, and MF374842). To complete Koch’s postulates, 10-µl aliquots of spore suspensions (106 spores/ml) of Rizo 05 and Rizo 07 were pipetted onto three non-wounded and four wounded asymptomatic grape berries (seven berries per isolate), Sterile distilled water was applied to asymptomatic berries to serve as a negative control. Berries were incubated at 25 ± 2°C in sterile moisture chambers, and the experiment was conducted twice (Ghuffar et al., 2018). Black to light brown, fluffy mycelium with the original symptoms was observed on both wounded and non-wounded inoculated berries after 3 days, whereas no symptoms were recorded on the negative control (Figure 4). The morphology of the fungus that was re-isolated from each of the inoculated berries was identical to that of the original cultures. Previously, Rhizopus stolonifer has been reported as a pathogen on grapes in Chile (Latorre et al., 2002). To our knowledge, this is the first report of Rhizopus stolonifer causing bunch rot of grapes in Pakistan. This finding will help to plan effective disease management strategies against Rhizopus rot of grapes in Pakistan.

Microbial Antagonism Toward Botrytis Bunch Rot of Grapes in Multiple Field Tests Using One Bacillus ginsengihumi Strain and Formulated Biological Control Products.

Botrytis bunch rot (BBR), caused by the necrotrophic fungus Botrytis cinerea, is a major disease of wine and table grapes worldwide. Due to negative effects of pesticides on the environment and human health, alternative control strategies against BBR, such as biological control agents (BCAs), are required to produce high-quality grapes and wines with high standards of food safety. However, few biological control products against BBR are available, and their efficacy is sometimes variable. This study aimed to evaluate and compare (1) the efficacy of new bacterial BCA strains developed at INRA Bordeaux and (2) the BBR reductions achieved by commercial biocontrol products that are already registered or close to being registered. During three consecutive seasons, 10 field experiments were established in six different experimental vineyards in southwestern France. Spray applications were performed at key phenological stages (five or six during the season), or at high BBR-risk periods late in the season according to a Disease Risk Index model. At harvest, BBR incidence and severity (% of symptomatic berries per bunch) were visually determined. The experiments included four bacterial strains at an early experimental stage, particularly Bacillus ginsengihumi (S38). Nine commercial BCA products were also tested, including Bacillus subtilis, Bacillus amyloliquefaciens, Aureobasidium pullulans, Ulocladium oudemansii, and Candida sake. Among the four experimental bacterial strains, only B. ginsengihumi S38 significantly controlled the BBR, presenting reductions in the average severity ranging from 35 to 60%, compared to untreated control, throughout the three seasons. Several commercial BCAs achieved significant reductions in BBR severity ranging from 21 to 58%, although not in every trial. The treatments that achieved higher reductions in severity rates were based on C. sake (45%), B. subtilis (54%), and B. amyloliquefaciens (58%). The efficacy of those BCAs was consistent throughout the studied seasons. The results confirmed the suitability of several biological control products under the conditions in vineyards in southwestern France, while also highlighting the good performance of the novel experimental BCA B. ginsengihumi S38 strain, which achieved similar control rates to the products registered for commercial use. The major factors involved in the variability in the results are also discussed.

First Report of Mucor fragilis Causing Bunch Rot of Grapes in Punjab, Pakistan

First Report of <i>Mucor fragilis</i> Causing Bunch Rot of Grapes in Punjab, Pakistan

A GC–MS untargeted metabolomics approach for the classification of chemical differences in grape juices based on fungal pathogen

Fungal bunch rot of grapes leads to production of detrimental flavour compounds, some of which are well characterised but others remain unidentified. The current study uses an untargeted metabolomics approach to classify volatile profiles of grape juices based on the presence of different fungal pathogens. Individual grape berries were inoculated with Botrytis cinerea, Penicillium expansum, Aspergillus niger or A. carbonarius. Grape bunches were inoculated and blended with healthy fruit, to provide 10% (w/w) infected juice. Juices from the above sample batches were analysed by GC/MS. PLS-DA of the normalised summed mass ions indicated sample classification according to pathogen. Compounds identified from those mass ion matrices that had high discriminative value for classification included 1,5-dimethylnaphthalene and several unidentified sesquiterpenes that were relatively higher in B. cinerea infected samples. A. niger and A. carbonarius samples were relatively higher in 2-(4-hexyl-2,5-dioxo-2,5-dihydrofuran-3-yl)acetic acid, while P. expansum samples were higher in γ-nonalactone and m-cresol.

Different levels of resistance to cyprodinil and iprodione and lack of fludioxonil resistance in Botrytis cinerea isolates collected from pistachio, grape, and pomegranate fields in California

Botrytis cinerea is the causal agent of gray mold disease and can infect fruits of important crops like grape, pistachio, and pomegranate, causing significant yield losses worldwide. In this study, mycelial growth assays in vitro were used to evaluate the sensitivities of 160 single-spore isolates of Botrytis cinerea collected from commercial grape (n = 58), pistachio (n = 74), and pomegranate (n = 28) fields in California to cyprodinil, fludioxonil, and iprodione. Based on the effective concentration at which mycelial growth was inhibited by 50% (EC50 values), 100, 83, and 38% of the isolates from the 3 hosts were sensitive (EC50 < 1 μg/mL) to fludioxonil, cyprodinil, and iprodione, respectively. Thirteen, 3, and 1% of the isolates showed low (CyLR), weak (CyWR), or high (CyHR) resistance to cyprodinil, respectively; Sixty-two percent of the isolates tested showed low resistance (1 < EC50 < 10 μg/mL) toward iprodione (IpLR) and were detected in all three hosts. Absence of cross-resistance was not observed between cyprodinil, iprodione, and fludioxonil. Sequence analysis of the two-component histidine kinase target gene (Bos1) revealed that some of the IpLR phenotype isolates were associated with either I365N/S, Q369P, and/or N373S mutations. Laboratory studies showed that IpLR, CyLR, and CyWR phenotypes were not associated with fitness penalties for mycelial growth rate on non-amended media and pathogenicity on detached grape berries. Furthermore, preventative applications of commercial formulations of iprodione (Rovral) and cyprodinil (Vangard) were effective against gray mold caused by Ip- and Cy-sensitive isolates, but failed to control disease caused by IpLR and, CyLR and CyWR isolates, respectively. The generated information will serve as a basis for implementing fungicide use recommendations against bunch rot of grapes, blossom and shoot blight of pistachio, and gray mold of pomegranate.

Pre-selection in laboratory tests of survival and competition before field screening of antagonistic bacterial strains against Botrytis bunch rot of grapes

With only a few biocontrol products currently registered against Botrytis bunch rot (BBR) of grapes, there is a crucial need for new antagonistic strains that are able to survive and efficiently suppress B. cinerea under vineyard conditions. The aim of this study was to establish and follow a pre-selection process among potential antagonistic bacterial strains, previously identified in vivo for efficacy, and to carry out a further field screening assay using a reduced strain number. Ten bacterial strains were pre-selected and tested, in vitro and in vivo, to characterise their mode of action and population dynamics under simulated climatic regimes. Four candidate strains were then selected and characterised for high efficacy in vivo, known mode of action and marked survival ability. Some suitable additives for increasing strain adherence on grape berry surface were tested prior to field applications, indicating one commercial adjuvant for potential improved bacterial persistence in the field. The four strains were applied separately in an experimental Merlot vineyard near Bordeaux (SW France), either at five key phenological stages, or following a specially developed Disease Risk Index (DRI). The Bacillus ginsengihumi S38 strain treatments significantly reduced BBR incidence by 72–75% compared to the control, whereas sprays applied according to the DRI decision support system tended to improve disease control. The study validates a laboratory pre-selection process followed by a field screening step, resulting in a candidate B. ginsengihumi strain S38 with a high potential for BBR biocontrol and future development in vineyards.

Cultural, morphological, pathogenic and molecular characterization of Mucor fragilis causing bunch rot of grapes in Pakistan and its bio management through plant essential oil

Cultural, morphological, pathogenic and molecular characterization of Mucor fragilis causing bunch rot of grapes in Pakistan and its bio management through plant essential oil

Efficacy of fenhexamid treatments against Botrytis cinerea in grapevine as affected by time of application and meteorological conditions

Grape bunch rot caused by Botrytis cinerea is one of the major fungal diseases of grapevine (Vitis vinifera L.) worldwide. Besides crop cultural measures, botryticides are used on a regular basis for controlling bunch rot. To investigate the impact of (i) the time of application and (ii) the meteorological conditions on the efficacy of a single botryticide treatment per year (active ingredient: fenhexamid), field trials were conducted over a six year period (2011–2016) on the cultivars Riesling and Pinot gris. The median levels of efficacy compared to the untreated control at 100 days after growth stage BBCH 68 were 6.7%, 23.1%, 34.8%, 25.6%, 16.0%, 34.5% or 9.0% for Riesling and 13.9%, 16.5%, 23.7%, 9.8%, 6.6%, 9.3% or 14.1% for Pinot gris for applications at 0, 2, 4, 6, 8, 10 or 12 weeks after BBCH 68, respectively. Generally, the levels of efficacy as well as the delays of the epidemics caused by the fenhexamid treatment (i) were lower than those attainable by cultural measures and (ii) decreased with increasing temporal distance between BBCH 68 and the date of assessment as well as with the level of disease severity. Results indicate that in Riesling, fenhexamid treatments before bunch closure and shortly after veraison were most effective, whereas this was the case for Pinot gris only around bunch closure. The rather low overall efficacies suggest that a limited number of targeted botryticide applications may represent a facultative component in the complex bunch rot control strategy primarily based on efficient crop cultural measures. The delay of the epidemic induced by a single fenhexamid treatment was significantly affected by the annual meteorological conditions in the different stages of grape development even outside the application period suggesting that plant physiological factors also contribute to the overall effect.

Characterization of Botrytis cinerea causing grape bunch rot in Chinese vineyards

Characterization of Botrytis cinerea causing grape bunch rot in Chinese vineyards

Overall efficacies of combined measures for controlling grape bunch rot can be estimated by multiplicative consideration of individual effects

Aims: The present analyses aimed at evaluating the performance of two models for estimating the overall effect of combining two or more measures (leaf removal, cluster division, late shoot topping, botryticide application, bioregulator application) for controlling grape bunch rot based on the efficacy of the individual measures.Methods and results: Field trials with the white Vitis vinifera cultivars Pinot gris and Riesling on the efficacy of three bunch rot control measures applied either alone or in combination were analyzed. Bunch rot disease severities prior to harvest were assessed and efficacies were calculated for each treatment. Observed efficacies of single measures were used to estimate the overall efficacies of all possible measure combinations. Calculated efficacies matched observed efficacies more accurately when assuming multiplicative interaction among the individual measures (R2 = 0.8574, p &lt; 0.0001; average absolute deviation: 7.9%) than in case of assuming additive effects (R2 = 0.8280; average absolute deviation: 14.7%).Conclusions: The multiplicative approach assumes that each additional measure is affecting (in case of efficient measures: reducing) the disease severity level as the result of the additional treatments rather than compared to the disease severity level in the untreated control.Significance and impact of the study: The high goodness of fit as well as the observed low deviations between the estimated and the observed efficacies suggest that the multiplicative approach is appropriate for estimating the efficacy of combined viticultural measures in a complex practical bunch rot control strategy assembled of different modules.

First Report of Botrytis Bunch Rot of Grapes Caused by Botrytis cinerea in Pakistan

First Report of Botrytis Bunch Rot of Grapes Caused by <i>Botrytis cinerea</i> in Pakistan

Flower Debris Removal Delays Grape Bunch Rot Epidemic

Field trials investigating the impact of removing flower debris (necrotic flower caps, filaments, anthers, aborted unfertilized ovaries, and aborted berries), which usually remain partly attached to grape clusters after bloom, on the epidemic of grape bunch rot caused by Botrytis cinerea were conducted in the white grapevine (Vitis vinifera L.) cv. Pinot gris (four experiments) and cv. Riesling (two experiments) in Luxembourg in the period of 2011 to 2014. Grape clusters remained untreated (control), or (i) flower debris was removed from the clusters (brush), or (ii) the clusters were treated with a botryticide (active ingredient fenhexamid; botryticide), or (iii) the clusters were brushed with a brush soaked in a botryticide suspension (botryticide-soaked brush) (all three treatments conducted at growth stage BBCH 73). On average of all six trials, bunch rot epidemics (day of the year reaching 5% disease severity) were significantly (p

GENETIC STUDY OF BOTRYTIS BUNCH ROT RESISTANCE IN GRAPEVINE

Grape bunch rot, caused by the necrotrophic fungal pathogen Botrytis cinerea, is one of the most destructive diseases in grapevines worldwide. At this point, control of Botrytis bunch rot is achieved through a combination of canopy management and fungicide usage. The identification of resistant germplasm could result in improved disease management. The Vitis aestivalis-derived ?Norton? is one of the very few commercial red grape cultivars that can be grown under elevated B. cinerea pressure where highly susceptible V. vinifera is difficult to grow. Tests on the F1 progeny from a cross between V. aestivalis-derived ?Norton? and V. vinifera ?Cabernet Sauvignon? may elucidate the underlying genetic and molecular mechanisms of berry disease resistance and berry quality. To this end, we have developed a population of 92 F1 genotypes from this cross that has yielded fruit for the past three years. Also, a linkage map employing simple sequence repeat (SSR) markers clustered in 19 chromosomes has been under construction. By using genotyping-by-sequencing (GBS) technology as part of the VitisGen (www.vitisgen. org) project, we aim to improve marker-density and identify the tightly linked markers associated with Botrytis bunch rot resistance. The overall goals of this study are to use genetic markers to rapidly implement favorable alleles and accelerate breeding cycles for new improved cultivar releases that warrant decreased pesticide use in the vineyard, resulting in greater environmental and economic sustainability.

Characterization and pathogenicity of Alternaria spp. strains associated with grape bunch rot during post-harvest withering

Alternaria is a fungal agent of grape bunch rot which occurs during withering, a process which produces passito style wines. Seven isolates of Alternaria spp. were characterized using morphological examination, genotypic analysis and pathogenicity. Six of these isolates produced conidiophores and conidia displaying sporulation patterns typical of the Alternaria alternata species-group. Variability in colony morphology and growth on different media was observed. Phylogenetic analysis of internal transcribed spacer (ITS) sequences clustered all isolates within a monophyletic clade, while intergenic spacer region (IGS)-RFLP profiles were congruent with those of A. alternata and Alternaria arborescens. RAPD-PCR proved helpful in discriminating between strains. To assay strain pathogenicity, grape berries were infected while undergoing withering conditions at different temperatures. Disease capacity was found to be strain dependent and varied consistently between the most and least aggressive strains. This study has provided interesting information on polymorphism within Alternaria spp. populations in withered grapes and on understanding the saprophytic role of this fungus during the post-harvest dehydrating process.

Grapevine Bunch Rots: Impacts on Wine Composition, Quality, and Potential Procedures for the Removal of Wine Faults

Bunch rot of grape berries causes economic loss to grape and wine production worldwide. The organisms responsible are largely filamentous fungi, the most common of these being Botrytis cinerea (gray mold); however, there are a range of other fungi responsible for the rotting of grapes such as Aspergillus spp., Penicillium spp., and fungi found in subtropical climates (e.g., Colletotrichum spp. (ripe rot) and Greeneria uvicola (bitter rot)). A further group more commonly associated with diseases of the vegetative tissues of the vine can also infect grape berries (e.g., Botryosphaeriaceae, Phomopsis viticola ). The impact these fungi have on wine quality is poorly understood as are remedial practices in the winery to minimize wine faults. Compounds found in bunch rot affected grapes and wine are typically described as having mushroom, earthy odors and include geosmin, 2-methylisoborneol, 1-octen-3-ol, 2-octen-1-ol, fenchol, and fenchone. This review examines the current state of knowledge about bunch rot of grapes and how this plant disease complex affects wine chemistry. Current wine industry practices to minimize wine faults and gaps in our understanding of how grape bunch rot diseases affect wine production and quality are also identified.

Determinants of fenhexamid effectiveness against grey mould on grapevine: Respective role of spray timing, fungicide resistance and plant defences

Botrytis bunch rot of grapes is mainly controlled by applying fungicides at three crop growth stages: the end of flowering (BBCH 68), bunch closure (BBCH 77) and the beginning of veraison (BBCH 81). The hydroxyanilide derivative fenhexamid is among the most effective fungicides registered to control Botrytis cinerea. Its effectiveness was examined in relation to spray timing, fungicide resistance and defense responses of grapevine. Overall, the earlier fenhexamid was applied, the more effective it was at controlling B. cinerea. Frequencies of B. cinerea strains which were resistant to fungicides were evaluated at harvest. The frequencies of resistant phenotypes were similar among treatments and years with the exception of a class of multidrug resistant strain (MDR 2) whose frequency appeared to increase after fenhexamid applications. If current spray programs including fenhexamid appear to control bunch rot at the current MDR frequency, a propagation of MDR 2 strains might lead to a decline in disease control. Finally, defense responses were studied in grapevine flowers/berries following fenhexamid application. None of the defense processes tested was induced in flowers/berries at stages 68 and 77. Only an increase in chitinase activity was observed in treated-berries at stage 81, suggesting that fenhexamid effectiveness was not related to a stimulation of defense responses.