Late winter or early spring is the best time to begin spraying an apple tree. Using horticultural oil spray helps to destroy any insects and their eggs on the tree before new growth begins.
Trees may be sprayed with antifungals during blooming, though it is recommended to do so at dusk or dawn to avoid killing tree-friendly bees. Apple trees should be sprayed about two weeks after most of their flower petals have fallen. This helps combat coddling moth larvae that bore into the fruit and eat it from the inside. A second application of insecticide should be applied a week after the first spray. This may be repeated if necessary.