As with all fruit trees, one factor of growing healthy apple trees and having an abundant crop is routinely applying insecticides to control insects and pests. As beneficial as insecticides are to apple trees, caution and care when using them is essential.
Dormant Oil Sprays
Oil sprays are used on apple trees beginning when the tree first begins to come out of dormancy and you see green leaves sprouting. Spraying apple trees with dormant oil spray early suffocates any eggs and insects that have lived over the winter. Reapply the dormant oil spray in two weeks and again just as the buds begin to form. There is no need to continue throughout the growing season. After the leaves have fallen, apply one last spraying of dormant oil to the apples trees before winter sets in. Do not mix dormant oil spray with other insecticides or fungicides.
Apple Tree Insecticides
Apple tree insecticides usually include the chemicals methoxychlor to control chewing insects and malathion or permethrin and carbaryl (Sevin) to control sucking insects, although there are many other effective insecticides. Multi-purpose sprays, which usually contain permethrin and carbaryl (Sevin), also may include the fungicide captan for disease control. For backyard apple tree growers, a multipurpose spray is easy and effective. However, depending on the type of pests attacking your apple tree, you may want to buy the chemicals separately.
Mix the insecticide per the label instructions and spray the apple tree a week after spraying the dormant oil spray. Continue an insecticide spraying schedule of every one to two weeks throughout the growing season, stopping four to six weeks before harvest. Do not spray your apple trees with insecticide while they're in blossom because the insecticide will also kill bees, which you need to pollinate your apple tree.