Kill as many resistant individuals as you can before you go back to last year's standby. Materials in the same family have the same mode of action and should not be used as alternatives or in tank mixes together. It is very important that sprayers be effectively calibrated. Uneven or poor coverage does become apparent when we are using a material which is highly effective in small dosages. But as resistance or tolerance increases poor coverage will mean poor control because not all the leaves or fruit received an effective dose.
Timely sprays are also important.
It is easier to prevent a disease from getting started than it is to stop its spread. Applying materials late to control a disease which is already present and spreading in your fields increases the opportunity for resistance increases dramatically because of the increased amount of inoculum in your plantings and the variability present in that population. These strategies are important for isolated growers. They are even more important in those regions of the state where there are large areas of a single crop growing. Once resistance gets started it can move through the entire region.