Spraying apple trees can prevent and control the infestation of codling moths and their worms that frequently destroy apple harvests. Apple worms start as eggs laid on the fruit by their moth parents. If the apple is not protected all through the growth season, it is difficult to break the infestation cycle as once the worm enters the apple it is protected from any insecticidal sprays.
When to Spray
Spray your apple trees for worms beginning in the late spring and continue on a spraying schedule through the late harvests in September and October, if applicable. Gauge your specific spray start date by counting 21 days after your apple tree is in full bloom. Establish an ongoing spraying regimen in keeping with the manufacturer's directions on the product you are using. This will likely result in spray applications made every ten days to five weeks, depending on the product used. Amend your spraying regimen with additional applications of insecticide after any significant rainfall, then simply resume the regimen you have established without delay.
What to Spray
To properly prevent and control an apple-worm infestation, use an insecticidal spray that contains malathion-methoxychlor. This formulation is almost always sold in liquid form, and is made under a variety of brands and names such as Sevin, Ortho Home Orchard Spray and Green Thumb Liquid Fruit Tree Spray. Always use the amount recommended by the manufacturer and apply it in the method that's recommended, making sure to wear the recommended safety equipment to avoid inhaling or ingesting the spray. Spray on a dry day with no rainfall in the morning hours to allow the spray to dry on the fruit and foliage before the night mists come.