Questions on: Apple Insects

Ron Smith, Horticulturist, NDSU Extension Service


Q: For many years, we have had an abundance of apples with worms in them. This makes the apples inedible. What should we be doing to get rid of the worms? (Mooreton, N.D.)

A: Spray using an insecticide, such as Sevin, at blossom drop and again in 10 to14 days. Spraying two more times after that should do the trick. You can try pheromone traps, if you can locate them. Put two or three traps in the larger trees. Picking up the apples that drop to the ground in the fall goes a long way in breaking the infestation cycle.


Q: I know this might sound stupid but when you say "mock apples" do you mean just any old fake apple or is there something called mock apples that are made for this purpose? I can't imagine why a maggot would get stuck on a plastic apple! (McClusky, N.D.)

A: They do sell apples, plastic or otherwise, that are covered with a tangle-foot type of material. The apples may contain pheromone that attracts the female adult insect. The insects die of dehydration after being trapped. You can also get the sex pheromone traps that attract the males into thinking there is a female within. Itís nasty to the insect but it works and is better than spraying a lot of indiscriminate insecticides.


Q: A gentlemen came into the office with an apple tree problem. His dozen or so apple trees (different varieties) lose their apples before they become ripe. The trees are planted in different areas of his farm. Some are planted in shade and some in direct sun but they all have been dropping their apples while they are still green. Is there something he can do? (E-mail reference)

A: Have him spray for apple maggots at blossom petal drop. I suggest he use Sevin, which should be applied at least twice, seven days apart. After that, have him purchase a few "mock apples" that will attract the female adult who will become stuck on the false fruit and die, unable to lay her eggs on the developing fruit. He should also pick up and destroy fallen apples throughout the summer. The trees in the shade will likely give him some additional problems later on.


Q:  On a TV gardening show the presenter talked about controlling insects in apple trees. He suggested painting a Styrofoam ball or something similar with red paint, suspend it in the tree and spray it with a sticky substance. Have you ever heard of such a control means? Would the sticky stuff be tanglefoot?  (Ellendale, N.D)

A:  Tanglefoot sprayed or smeared on an apple shape that is painted red will attract the female apple maggot and keep her away from the real apples. A couple per tree should work fairly well for the backyard orchardist.


Q: I have been looking for a spray to fight apple tree maggots. The material that I had last year was a liquid that was mixed with water and sprayed on the apples while the apples were small and the moths were present. As I recall, I believe it had the chemical substance Diazinon. I was told that this substance has been taken off of the market. I have an advanced degree in chemistry so I checked several references that I have. It is a somewhat toxic material if not handled properly. What can I use in place of this material and where can I purchase the material? I do a late summer and fall clean up of the apples that have fallen to the ground. However, others in the neighborhood do not do a clean up. (Faulkton, S.D.)

A: You are correct in your findings. Actually, apple maggots lend themselves quite nicely to pheromone control. If you have a good garden center or garden supply store in your area, they will likely have pheromone traps that you can hang in your tree (I suggest three per tree the initial year) and will catch the adult male preventing copulation and resulting offspring that will damage the apples. That same garden center may also have false apples that are covered with a sticky substance that holds the insect there once they land on the surface. No control, either chemical or organic, is 100 percent effective. But I have found that these two methods do an excellent job of greatly reducing the number of affected apples -- along with good sanitation practices like you say you are following. And of course, you don't put any toxic chemicals into the environment!


Q: Last fall the wasps got in our apple tree. What they didnít eat they just crawled in. so we got no apples. Is there something we can spray them with so it doesnít happen again, and when would be the time to spray? Also, we have a May Day bush that is about 8 feet tall and a few years old. Can we now trim it, after itís done blossoming, so it would be more of a tree?

A: The best control is to locate the wasp nest and have an exterminator take care of the problem. Donít spray the apples. Yes, the May Day bush can be pruned into a tree!


Q: I have a variety of apple trees (Granny Smith, Red Delicious, Yellow Delicious) probably about five years old. One of my Red Delicious trees has a couple of branches with a powdery white substance, and when you wipe it off it turns a reddish/brown color. This will be the first year that some of the trees are flowering. What do you suggest to control this type of fungus? (E-mail reference, Charlotte, N.C.)

A: I am afraid that the white substance you are referring to could be a family of soft scale insects deciding to take up residency on your tree, and the reddish-brown stuff is the blood from the crushed bodies. You should be well past the blossom time for the tree. If you can get some horticultural oil, spray it carefully on the affected areas that you can find. This is a light-weight oil that will not burn the foliage (follow label instructions!) when properly used. It kills the insect by cutting off the oxygen supply and is not an environmental hazard since it is usually composed of vegetable oils. There are other more potent materials you can use, but with an edible crop like apples I donít like to recommend them unless absolutely necessary.


Q: Can you tell me what is the matter with our apple tree? There is a heavy brown web on the branches and the foliage has died on those particular branches. Something also has been spinning a web around the apples and eating the fruit.

Also, our 30-year-old spruce trees are losing their needles this summer. Do we have some type of mineral deficiencies? (Page, N.D.)

A: You must be seeing the work of the fall webworm. If it makes the nest of webs over branch ends, that's what it is. Apples are high on its culinary list! The best control is to cut off the branch ends that have the webbing and burn them. Next spring, initiate a spray program as if you were controlling codling moth, using products containing carbaryl, diazinon or malathion. That will take care of any new interlopers!

It sounds like the spruce have a disease known as needlecast. You can control the further decline of the trees with a spray program using Bravo in June and July.


Q: Can you tell me what is causing the apples to fall off of our tree too early? The core of the apple is outlined with red streaks, which gradually spread through the apple causing it to lose its crispness. Also, will it spread to the other apple trees we have? (Conde, S.D.)

A: It sounds like you are having a problem with the great tunneler of apples, the apple maggot. Good sanitation, meaning fallen apple cleanup this autumn, will help control this pest.

Also, spray the tree twice: once in early spring to sanitize it before leaves open, with lime-sulfur, and again at flower petal drop to control the insect, with Sevin insecticide.


Q: When would I need to spray apple trees for both fireblight and insects? (Butler, P.A., e-mail)

A: Spraying apple trees for fireblight should be coordinated with weather conditions. As your area enters into a hot, humid spell, that would be a good time to spray for preventative measures. Check any fast-growing shoots for infection from the bacterium. It will be quite evident as you likely know. If a strong summer storm should blow through your area with high winds and hail that cause damage, spray within 48 hours after the storm has passed to provide protection. Now, spraying for insects is something you should do only in response to a problem, existing or threatening. If you have trouble with apple maggots, you need to spray before the females lay eggs in the developing fruit, especially if you are growing Wealthy, Delicious or Cortland varieties. The best practice is good sanitation--cleaning up all old apples remaining on the tree or apple drops from previous years. Check with your local county extension office to see what is labeled in Pennsylvania for spraying apple trees.


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