Question
When I hull the walnuts, and some are really black, there are these maggot looking worms inside - what are they?

Answer
WALNUT HUSK MAGGOT,RHAGOLETIS SUAVIS (LOEW) AND
WALNUT HUSK FLY,RHAGOLETIS COMPLETA CRESSON

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.

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.

Control
   Most home orchardists ignore the walnut husk fly because generally it does not affect the nutmeats. It can make the husks difficult to remove; however, this problem can be remedied by placing the damaged nuts in a damp burlap bag for a few days before attempting to remove the hull. Be sure to dispose of infested husks in a tightly sealed bag.

Certain general sanitation practices that reduce the number of husk flies overwintering near your tree or orchard may contribute to control. These practices include removing and disposing of damaged nuts as soon as possible. It may also be possible to reduce next year抯 population by spreading a tarp under the tree from July through August to prevent the maggots from entering the soil to pupate.

If gardeners feel a treatment is necessary in home orchard situations for trees with early or severe infestations, multiple applications of malathion and bait can be made beginning in July. Spray on a 21-day interval until within 1 month of harvest梕ggs laid later than this will not have time to develop and cause damage.

Bait is added to the spray as an attractant so that the flies feed on the spray. When bait is used, the entire tree does not need to be sprayed; spraying the lower half of the tree is adequate. Commercial growers use baits (Nu-Lure or Mobait) that are sold only in large quantities. Although research is lacking, molasses may work as a bait in backyard situations when added at 1 to 1.5 times the amount of malathion. For example, if you use 2 teaspoons of malathion per gallon of water, then add 3 teaspoons of molasses to the mixture. Follow label directions to determine spray rates for malathion.