PECAN WEEVIL (PW): Curculio caryae (Horn) Order - Coleoptera: Family - Curculionidae

DISTRIBUTION: PW can be found in pecan growing areas from New York to Iowa, south to Oklahoma and across the southeastern states from Florida to Texas. PW is occasionally found in New Mexico.

DESCRIPTION : Eggs (Fig 2) are small (1-2 mm), white, oval, and usually laid on the developing nut kernel; there are three to four eggs per nut. Larvae (Fig 3) are 10-12 mm long when mature. They are creamy-white, legless, and C-shaped with dark reddish-brown heads. Pupae (Fig 4) are creamy-white, resemble adults and are found in earthen cells 10-30 cm deep in the soil near the host tree. Adults have a body length of about 12 mm and are light brown to gray with a very long curved beak. Males have a shorter beak.

HOSTS: Primarily pecan and hickory and to a lesser degree walnuts, oaks, beech, and hazelnut.

DAMAGE: Weevil feeding during the early “gel” stage of pecan development can cause nuts to drop or can result in "sticktights" where the shuck adheres to the nut, interfering with processing. Adult feeding (Fig 5) and egg laying can also leave characteristic circular feeding scars on the surface of the shuck around the beak entrance hole. Larval feeding within the pecan causes complete destruction of the kernel.

INSPECTION TIPS: Burlap and sticky bands are used to collect adult weevils crawling up tree trunks. Knockdown sprays and assorted non-pheromone traps are also used to survey for adults. At harvest time open and inspect nuts, especially those with shucks adhering to their shells. Check debris around processing equipment. Open and inspect nuts found with exit holes (Fig 6). Inspect soil under host trees to a depth of 10-30 cm and fallen nuts for larvae, pupae, and adults.

LIFE CYCLE: PW have a very long development time – two or three years. Adults emerge from the soil near their host trees shortly after heavy rains, usually in August, and start feeding and looking for mates. Females must find pecan nuts in the “gel” stage prior to nut maturity and shell hardening for egg laying to be successful. Adult females use their long beaks to chew to the developing kernel, where they lay three or four eggs. Eggs hatch in 6-14 days, and larvae mature in 40-45 days. Mature larvae exit the nut through a 3-4 mm diameter hole and drop to the ground. Once on the ground, the larvae burrow into the soil 10-30 cm and form earthen cells. Larvae spend almost a year in their earthen cells before pupating. The pupal stage lasts about 3 weeks. Most remain in the soil as adults for another year – a two-year cycle. A few delay pupation for an additional year – a three-year cycle.

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