They appear during the latter part of July and lay their eggs in punctures in the husks of the growing nuts. It may impair the quality of the kernel within the shell, or cause the husks to stick to the shell, or may be in part responsible for blackening the shells which makes the nuts unattractive. Infested nuts may fall from the tree prematurely, however, many remain on the trees long after normal nuts have fallen to the ground. When the maggots are fully grown in the fall they leave the husks and enter the soil where they pupate and emerge as flies the following year. The adult flies are nearly as large as the common housefly.
Some control has been obtained with sprayed insecticides, however, the results are inconsistant.
Malathion when applied before egg laying occurs may be of some help. The first spray should be applied about mid-July and continued twice thereafter at weekly intervals for a total of three applications. Some control may also be obtained during harvest. Collect the nuts before the maggots emerge from the husk and place them in tubs or buckets partially filled with water. The maggots will drown and the fly population will be greatly reduced during the following year.