When conditions for downy mildew are expected, consider spraying once every 7-14 days with applications of fungicides. Don’t use products based upon the same active ingredient in consecutive treatments. Use of fungicides belonging to different groups to prevent pathogens from developing resistance to a specific chemical.
The following is a list of generic names of fungicides (sorted by groups) and used in one or more parts of the world:
Group 1: Cellulose synthesis inhibitors such as Dimethomorph and Mandipropamid, Iprovalicarb, and Benthiavalicarb – isopropyl
Group 2: RNA inhibitors such as Metalaxyl – M
Group 3: Respiration inhibitors such as Fenamidone and Propamocarb HCL+Fluopicolide
Group 4: Resistant inductors such as potassium salts of phosphorous (phosphoric) acid