Question
Our Walnut tree has small white worm like insects beteen the nut and the green coverning.  Can you tell us how to cure this.
Thanks,
Sharon

Answer
Sounds like the walnut husk fly.

The walnut husk fly and the walnut husk maggot both occur commonly throughout central United States.


   The walnut husk fly and the husk maggot look alike. They are light brown in color and have two transparent wings with dark cross bars. They are smaller than the house fly. The larvae of both species are legless and pale yellow in color. Full grown larvae are up to 1/2 inch long.

Injury
   The walnut husk fly and the walnut husk maggot breed and lay eggs in the husks of nearly mature walnut fruits in early autumn. The larvae burrow into and feed on the husk, producing black, slimy husks that stain and stick to the shell. The maggots can sometimes be seen crawling in the husks.

   Husk maggots and husk flies do not penetrate into the nut, so the taste and color of the nutmeat are not affected. However, the slimy nature of the husks reduces their value to commercial nutmeat producers because the husk is difficult to remove. The infested husks also make the nuts unattractive and undesirable to the private walnut grower.

This small fly spends most of its life cycle underground but emerges in summer to lay eggs in the hulls of maturing walnuts. Hulls of infested nuts turn black and are often mushy and full of maggots; meats often fail to develop or become moldy. If you're lucky, only the shell will be stained and the nut will be edible, although messy to hull; wear gloves.

It's very difficult to control walnut husk flies on a single-tree basis. If there are many trees in your area, your entire neighborhood will need to be sprayed.

About the only thing that can be done unless the tree is sprayed with an insecticide is pick up any nuts with the damage and destroy them.  Insecticides used are Malathion EC. Fruit & Berry Insect Spray.