Keeping surrounding woods and fields free of alternate hosts for pests will also lessen the need to spray. Early season mowing discourages two spotted mites. Research into the life of the pests in question has cut the use of pesticides. For example apple scab, a fungus that growers spend more time and money combating than any other single pest, has been extensively studied with respect to the conditions necessary for an infection to occur. Scab spores which over winter in the apple leaves which fell the ground the previous autumn are released by rain at a time when the spores are mature and ready to shoot.
Infection depends upon the temperature and the length of the wetting period.
Growers get information from University Extension specialists about the current maturity of scab spores, monitor the temperature during rain and the length of the wetting period and then look on a chart to determine if conditions were right for an infection. If so measures can be taken to combat it. Some growers use spore traps that face into the wind, suck in the air and deposit any spores on a microscope slide. The trap has a switch that is activated by moisture and so turns on when it rains. The other approach used is to watch weather forecasts for approaching rain and to make sure that the trees are covered with a protectant fungicide ahead of time.