Immunox- specticide multi purpose. this is a systemic that last 14-21 days and the second app in 2 weeks is cumulative and the combo application last about 45 days. That brings us to mid july but really the Immunox hangs on an protects a bit longer.
Mid July- Daconil or any concentration of Chlorantanil which is a contact killer that last about 10 days as long as it doesnt rain but the Chloroanthanil is much safer than the Immunox.
The combination will prevent the disease and save your crop if the disease is present in your area. If youve had it in the past 5 years, dont wait. It will cost you your crop in a heartbeat.