I have a problem with an apple tree, which has been infested with a mite for a number of years. I planted the tree 20 years ago. The first few years the tree bore fruit and we had wonderful yellow delicious apples, great for apple sauce and pies. After four or five years I noted small black pits appearing shortly after flowering while the small apples were forming. These pits progressed as the apples grew. Pitted apples would fall off all through the growing season and those that grew to full size were riddled with rot.
I also noted small white spongy masses on the tree that seemed to accompany the pitting through the season. When these white masses were minimal, more apples seemed to reach maturity.
Here are some of the counter measures I've tried: fruit tree sprays of all kinds; heavy pruning; dummy apples coated with paste; pouring Drano around the base; consulting with several nurseries, who recommended a sulfur product.
None of these measures seem to have injured the tree, but the mites are returning each year. I get full flowering starting very soon, so if you can suggest any other measures prior to budding, please do so. J.H.,
We suggest you regroup and find out what the problem is. What you've done reminds me of bleeding -- that discarded medical remedy in which physicians faced with anything from high fever to hysteria would “open the veins and let blood.” Now that science has exposed the nature of many ailments, we know that bleeding was useless and may have made things worse by weakening the patient or providing openings for additional infection.
We've made scientific advances in gardening, too. For instance, we know mites don't pit apples. They are sucking pests, living on foliage. If a mite infestation is so heavy that a tree's energy level falls, fruit production might also drop, but the mites never directly damage the apples.
Pitted fruit may be apple maggots' work, according to Oakland County MSU Extension agent Greg Patchan. “It's one of the toughest fruit pests to control, if only because people can't pinpoint the problem. They may not find any ‘worm’ eating the apple because it's so tiny or it may already be gone by the time we look. Fake fruit with sticky coating won't control this pest -- that's just a way to know when the adults are around and laying eggs. Adults are black and white flies similar in size to house flies.”
Adult apple maggots emerge from the soil beginning in July each year and lay eggs in developing apples. The hole made to insert an egg is so tiny we usually don't notice it, but it's the start of a slender, white maggot which eats until it's ready to pupate. Then it makes a small but noticeable exit hole, drops to the ground and wiggles into the soil where it transforms into an adult. New generations hatch until natural signals such as falling temperatures put the last batch of maggots on hold in the soil over winter. (Pouring Drano won't kill them. Very little affects these insects when they're protected by soil and a pupal case, too.)
Soft rot fungus infects the apples through exit holes and maggot trails -- the more maggot damage, the more rot gets in. Badly infected apples fall, incidentally shortening remaining maggots' trip to the soil.
This is what your problem MIGHT be, not a certainty. The best way to control apple maggot or any pest starts with positive identification. So put out those sticky apple lures in late June. When you see flies caught there, take the insects plus a few new fruits to your Extension for diagnosis. Extension can identify pests and dispense inexpensive, detailed, scientific bulletins that explain how to control problems on almost every outdoor or indoor plant which gardeners, farmers, orchardists and foresters might grow. Check the directory or on line for your county's Extension or Cooperative Extension office.
If apple maggot is the culprit, you can spray with an insecticide listed on those Extension bulletins, beginning when adults are detected. Also be sure to destroy all fallen or infected apples. Hot compost them, burn them... or cook them. We've heard many times that cider and applesauce made from “damaged” apples can be particularly tasty and nutritious!