Three good types of insecticidal sprays for apple trees are horticultural oil, bacillus thuningiensis kurstaki and phosmet. These sprays help control infestations of apple maggot flies, plum curculio and codling moth.
Horticultural oil helps control many different pests in apple trees by smothering dormant insects and their eggs. It is sprayed in spring before new leaves grow. Bacillus thuringiensis kustaki kills the larvae of the codling moth and is sprayed in the evening 15 days after the petals of the apple blossoms start to fall.
Phosmet helps control the plum curculio beetle and is sprayed immediately after petals start to fall, and then again one week to 10 days later. Avoid using all purpose fruit sprays because they may harm beneficial insects.