Quince are about the "buggiest" fruit I've ever seen -- it's really, really hard to get nice, smooth fruit without a lot of insects in them. They are attacked by the plum curculio early in spring, which causes them to become misshapend and deformed. Then, they are attacked in late spring/early summer by apple maggots, and finally later in the summer by coddling moths, which tunnel through the fruits causing great big, dead, brown patches which rot. What a mess.

OK, the simplest way to deal with this is to do a couple of good, heavy sprays right away at petal fall and about 10 days later -- Imidan is a good product, since it is one of the few things which actually controls plum curculio.

THEN, bag your fruit. Since quinces are probably NOT something you need by the bushel, it's relatively cheap and easy to select and bag them -- 50 to 100 fruit would probably be all anyone could need.

There has been quite a bit about bagging fruit on these forums. Do a search and a lot will pop up.

Alternative to bagging is heavy spraying all summer.

Richtext:

Perhaps neem oil will work for you, but it did not for me. I used pure cold-pressed neem oil with an added emulsifier for an entire season on apples and stone fruits with no positive results I could note. Sprays with neem were spaced about a week apart, but insects and diseases flourished as if I had not sprayed at all. I discovered that neem oil softened the seals in my sprayer and made them leak, and I also had to replace the pump plunger. That ended my neem oil trials.

Now I use imidan and permethrin for early insects, and ferbam and streptomycin for my most serious diseases, which are cedar apple rust and fireblight. As soon as the fruits are large enough for final thinning, I bag them and am able to stop spraying for the balance of the season. However, I also dormant spray twice during early and late winter with oil and copper on all the pome and stone fruits. This reduces or eliminates some insect and disease problems like aphids and apple scab.

I often hear the term "harsh chemicals" used, but it has little meaning for me. I have a long spray wand, spray only in optimal low-wind conditions, and carefully target the spray to the trees, not myself. I believe the minimal early spraying I do leaves virtually no residues by harvest time several months later when the fruits grow up. The sprays are certainly not harsh for the trees and fruits, which are much healthier thanks to their use.

Don Yellman, Great Falls, VA