An Effect and Less Spraying Control Method Successfully Controls Botrytis cinerea on Grapes in China

Gray mold caused by Botrytis cinerea is a destructive disease in grapes. Although the preharvest use of pesticides can control it, fungicide resistance in B. cinerea is now common. We used an Effect and Less Spraying Control (ELSC) method for applying fungicides effective against B. cinerea on grapes. The spraying schedule was determined by exploring the key stages of B. cinerea invasion using field and in vitro inoculation tests. The results indicated that the stage most vulnerable to pathogen invasion is the full-bloom stage. The disease incidence/severity in this stage is highest compared with the pre-bloom, 10-days-after-full-bloom, bunch-closure and veraison stages. Given the inoculation results and the threat of residual infected petals, the ELSC method established an optimum spray schedule at full bloom and 10 days after full bloom. To evaluate the ELSC method, four kinds of fungicides were used in an experimental trial in Beijing in 2015 and 2017; Shanghai in 2016; and Hebei in 2019 and 2021. Fludioxonil was the most effective fungicide, followed by Pythium oligandrum (bio-fungicide), difenoconazole + azoxystrobin and pyraclostrobin. ELSC was more effective against B. cinerea than the traditional control schedule, when comparing the disease severity (i.e., 0.07 +/- 0.10% in ELSC and 0.49 +/- 0.014% in the traditional practice when using fludioxonil). The average yield per hectare in ELSC confirmed that spraying during flowering does not have a deleterious effect on grape yield. It produced a 1224.37 00 kg/ha greater yield than the control group when fludioxonil was applied.