Name: Rhagoletis completa

Alias: Walnut Husk Fly. Adults are about the size of a housefly, with an obvious yellow dot on their back where their wings are attached. The wings have distinct dark bandings. They emerge from their pupa stage in mid-summer to find a mate and lay eggs. The larvae are small white maggots that are protected by the husk of the walnut. The larvae emerge from the fruit and drop to the ground to pupate.

Crimes: As the larvae feed they leave unsightly splotches on the nutshell, lowering the nut quality. The damage is mostly cosmetic, so the biggest concern for home owners is opening an unripe fruit and getting grossed out. There is no tolerance for walnut husk fly in commercial orchards.

Redeeming Qualities: none known.

Sentence: For home orchards there may not merit a need for control. The damage is unsightly, but tolerable. Because the eggs and larvae are protected by the husk of the fruit, the adult form is the best stage to target for control. The best tool for monitoring for walnut husk flies is using yellow sticky traps that are baited with ammonium carbonate. These sticky traps let you know when the flies have arrived and when to start control methods. Insecticides should be applied as husk flies appear on sticky traps. For home orchards options are limited, but some examples are pyrethrins and Spinosad. For commercial orchards there are more options. Timing is more critical than which chemical is chosen. Always read and follow label instructions.

For more information on dangerous and beneficial bugs, call UI Extension educator Joseph Sagers at 208-745-6685 or email

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