Black Walnut Curculio: Appearance, Territory, Damage and Life Cycle

Latin Name: Conotrachelus Retentus

Appearance: Conotrachelus R (Coleoptera: Curculionidae) flight and dispersion behavior was shown to be constant across spring and summer adult populations. Female curculios flew higher down the bole of a walnut tree than males did. Curculios distributed fast inside the crown of the black walnut tree into which they were discharged, but there was limited dissemination.

Hosts Plants: Walnut

Territory: Eastern North America

Damage Insect Cause: The black walnut curculio is a little bug that may cause significant damage to black walnut harvests. Trees afflicted with the black walnut curculio might lose up to half of their nuts. Because black walnut curculio eats mostly at night, they are frequently overlooked until the nuts have been injured and it is too late. There are various pesticides on the market designated for curculio control, however spraying is challenging due to the great size of black walnut trees. In late April, one method of combating black walnut curculio is to hammer on limbs, forcing them to fall off of the tree. To collect and dispose of them, use a drop cloth. Collect the nuts that fall from the tree in June, take them away from the tree, and dispose of them. This will keep the black walnut curculio population under control.

Life History and Habits: Conotrachelus Retentus is a black walnut curculio pest that oviposits on individual nuts in the spring, immediately after pistillate flower fertilization. Oviposition and nut feeding continue till June. A mature female lays a single egg in a crescent-shaped slit eaten into the fruit’s hull. Despite the fact that many oviposition sites on a single nut result in multiple first-instar larvae, the most aggressive larva often swallows the others. The larvae grow within the nuts, causing normal development to be disrupted and resulting in “June nut drop.” Larvae emerge from the nuts and pupate in the soil. Adults emerge in late summer to feed on walnut foliage until the leaves fall, at which point they overwinter in leaf litter.