While white grubs are present in the soil in spring, they are not causing serious damage to the turf, so treatment in spring is a waste of time and money. The most appropriate time to treat them is late July, when there is the most potential for damage to the lawn. Not all problems warrant chemical treatments. For example, the plant bug is an insect that attacks the honey locust tree. While it deforms the foliage in the spring, the bugs stop feeding early and the tree looks healthy by mid-July.
Insecticides can also kill butterflies and beneficial insects such as ladybugs and bees.
Likewise, disease problems need to be treated at different stages of their development. Spraying for peach leaf curl after the buds break will not be effective. Peach trees must be sprayed while the buds are still closed in order to control this disease. There are some plant diseases for which there are no chemical controls. For example, there is no known cure for Pine Wilt, a disease that is fatal to Scotch Pines.