|WANG, FEI - University Of California, Davis|
|MILES, TIM - Michigan State University|
Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/30/2021
Publication Date: N/A
Technical Abstract: Powdery mildew (PM) causes severe loss of table grape production worldwide. To control the causal agent, Erysiphe necator, fungicide spray programs have been largely applied in the grape vineyards. However, frequent sprays might also have an effect on populations of non-target fungi. For example, several PM fungicides are also used to control Botrytis cinerea that causes postharvest gray mold in table grapes. Therefore, this study aims to investigate the effects of different PM fungicide spray programs on non-target fungi populations and distributions in grape vineyards. We studied two fungi species, Botrytis and Alternaria, collected from three grape vineyards in California: one field with six PM spray programs (treatments) and two fields with one PM spray program for each. Single-spore cultured Botrytis and Alternaria isolates were obtained from the leaf or rachis samples collected from each treatment between the bloom and the fruit set growth stages. The isolates were evaluated and analyzed for: (1) the fungicide resistance phenotypes for three common botryticides, pyraclostrobin (QoI; FRAC 11), boscalid, and fluopyram (both SDHI; FRAC 7), (2) colony type for morphological characterization, and (3) phylogenetic analysis for species identification. The results showed that both Botrytis and Alternaria isolates displayed differential populations in their fungicide resistance phenotypes under different treatments, suggesting PM spray programs have varying effects on non-target species such as Botrytis and Alternaria species.