Plenty of small unripe apples on multiple trees face the same fate. What bug is causing this and what are some methods to counter the attack?
Codling moth would be my thought. Lots of sprays will control them. WE don’t have them here. Father north in Amarillo they were terrible. Carbaryl works great but can cause spider mite outbreaks.
Looks like you’re right.
Control is extremely difficult, and if there are any oak trees as street trees nearby you’re doomed, as they are a host. Spray timing and frequency is critical, for most people bagging is the only sure way. Some varieties ripen later and miss infestation; Lady Williams, King David, Dixie Red Delight, Sundowner, and Pink Lady usually do OK. Fuji gets hammered.
Are you saying oak trees are host trees of codling moth? Are they what infests some of the acorns?
Yes, you’ll see a little hole in the side of the acorn.
Wow! Our neighborhood is full of oak trees. I never knew that. Thanks.
Uh, the photos from the OP don’t seem like codling moth to me. Generally the tunnel entrance is plugged with a mound of frass.
Likewise, I’ve only ever heard of codling moths infesting apples, pears, walnuts, chestnuts, and rarely apricots (Wikipedia). There may be strains of codling moth that prefer nuts over pome fruit. The infestation of oaks in the U.S. may be an acorn moth.
Most of the apples have a mound by the entrance/exit. This one just happen not to have that, or it was brushed off. I can certainly provide other pictures of other apples if needed.