Pecan Weevil: Appearance, Territory, Damage and Life Cycle

Latin Name: Curculio Caryae

Appearance: Curculio Caryae (Coleoptera: Curculionidae), the pecan weevil, is native to North America and feeds on the nuts of trees of the genus Carya. It is a major pecan pest that may cause significant economic harm if not managed. The brownish weevils are around 10 mm long, and the female’s narrow snout is as long as her body. Both male and female adults feed on growing nuts, causing them to shrivel or drop if feeding happens before the nuts reach the gel stage.

Adults are hard-shelled beetles with long, narrow snouts and slender legs. They’re about a half-inch long and range in hue from reddish brown to gray. The female’s nose is somewhat longer than the male’s, while the male’s snout is little shorter. A pair of long, elbowed antennae are joined around the center of the snout. The larvae are creamy white legless grubs with soft, squishy bodies and reddish-brown heads.

Hosts Plants: The pecan is the sole economic host, where feeding and breeding occur in maturing nuts. The pecan weevil will breed in hickory nuts as well.

Territory: The pecan weevil is the most common pecan insect pest in Oklahoma and across the Caryae Illinoisans natural range.

Damage Insect Cause: Adults eat on nuts by puncturing the husk and shell when they emerge from the earth. If the nuts are still wet, they leak fluid through the puncture and fall off the tree two or three days later. The brown marks on the exterior of the husk identify these injured nuts. The larvae eating within the nut do the majority of the harm. Inside each nut, one to four larvae hatch and consume the entire kernel.

Life History and Habits: From late July through October, adult weevils can be discovered in the soil, generally after rain has softened the ground. Peak emergence usually happens between August 10 and September 20. In years of severe drought in August, peak emergence may be delayed until September or even later. When the weevils emerge, they proceed to feed on the pecan nuts and mate. Egg laying begins when the weevils encounter nuts in the gel stage. The female drills a hole in the nut with her snout and then lays one to four eggs in the expanding kernel. Before maturing, the larvae hatch and feed on the kernel for around 30 days.