When and what to spray depends on what pest you are trying to control. If the timing of the spray isn't correct, then it won't be effective and you may end up harming beneficial insects and pollinators instead. So, proper diagnosis of the problem is the first step. If you see signs or symptoms in your apple tree and need help with diagnosis, you can send photos and a description of the problem to the Lane County Master Gardener plant clinic at <personal data hidden>. For information on managing insects and diseases in home orchards, refer to the following OSU Extension publication: https://extension.oregonstate.edu/catalog/pub/ec-631-managing-diseases-insects-home-orchards.

Most likely the larvae are from the codling moth (Cydia pomonella) or apple maggot (Rhagoletis pomonella). With codling moth, the tunneling will go all the way to the core of the fruit, and you may see holes on the exterior of the fruit with frass (insect poop) falling out. Typically the holes appear in May and June, and again at harvest. With apple maggot, the tunnels caused by the larvae will meander through the flesh of the fruit. The holes in the fruit, if present, won’t have frass in them, and the holes typically only appear at harvest.

For coddling moth, timing of the spray is important, and we recommend using pheromone traps. We (OSU Extension Lane County) placed several codling moth traps around the Eugene-Springfield area. Mass captures were reported in several traps on 5/14/2024, which was set as the biofix date and starting point for accumulating degree-days for the Brunner and Hoyt model. Based on the model, sprays for the first generation of codling moth should be made on June 9th, June 20th, and June 28^th in the Eugene-Springfield area and south Willamette Valley. By June 9^th, eggs will begin hatching. At this stage horticultural or neem oils are effective in smothering the eggs and tiny larvae that hatch out. These neonate, or newly hatched larvae, are very tiny and they do a bit of feeding before they are able to find and enter the fruit. Once they enter the fruit they can no longer be treated. Refer to the PNW Handbook for a list of chemical control for HOME USE: https://pnwhandbooks.org/insect/tree-fruit/apple/apple-codling-moth

If you don’t want to spray pesticides or want to reduce their use, there are a few cultural practices that can be used in lieu of or in conjunction with pesticides. Sanitation is the most important practice that is environmentally safe. If you remove and dispose of damaged young fruit throughout the season, you can help reduce future generations. Larvae continue to feed inside the fruit after it falls from the tree, so remove infested and fallen fruit promptly. “Fruit sox” or bagging individual fruit in paper or mesh bags can be effective, but you need to get the bags/sox on before June 8^th. Thin clusters to one fruit before placing the bags over them. Fruit will mature completely within bags, however color development on red varieties may be affected.Homeowners can also place corrugated bands of cardboard around the lower trunk to attract larvae looking for a place to pupate. Place bands in May and remove before the adults begin to emerge in early to mid-June. The same technique can be used for the subsequent generation(s) later in summer.

For apple maggot, yellow or red sticky traps are recommended for monitoring. You can purchase one of the red plastic apples that are covered with sticky glue, those have been fairly effective for home gardeners. Traps need to be placed in the upper and outer canopy of the tree by mid-June. As a home gardener, removing infested fruit from the tree and fruit that has fallen to the ground, is one of the most important practices. You can also use the fruit sox or bag individual fruit to protect them from egg laying flies. The bags need to be in place by mid-June. Kaolin clay acts as a repellent by coating the trees in white and confusing the adult flies. Kaolin clay needs to be applied starting in late June.

Sprays for apple maggot should be made in mid to late July. Products such as neem oil and pyrethrins are registered for use in home gardens. You will find more information on apple maggot and management practices in the PNW Handbook: https://pnwhandbooks.org/insect/tree-fruit/apple/apple-apple-maggot
and this WSU Extension publication https://pubs.extension.wsu.edu/protecting-backyard-apple-trees-from-apple-maggots.