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Scientific Name: Conotrachelus hicoriae
The adult nut curculio attacks immature pecans from
mid-July to mid-August. Females make shallow, crescent-shaped punctures
with their beaks in the shucks of immature nuts, and they deposit a single
egg in each nut. The eggs hatch in four to five days, and the larvae feed
for 10 to 14 days. This puncture and the larval feeding cause a bleeding
of brown sap on the nut shuck at the point of entry and also premature nut
drop. The damaged nuts drop from the tree in late July to late August, and
the larvae continue to feed in the fallen nuts for about two more weeks.
The larvae exit through a one-sixteenth inch hole and enter the soil. The
adult nut curculio emerges four weeks later, from September to October,
and overwinters in ground trash or other protected places. The nut
curculio produces one generation a year and rarely is economically
damaging.
Adults are dark-gray to reddish-brown and are
three-sixteenths of an inch long, with the beak about one-third the body
length. Larvae have no legs or prolegs and are creamy-white,
three-sixteenths of an inch long and found within immature pecans.
People often confuse damage from the nut curculio with
that of the hickory shuckworm. Usually trees adjacent to woody areas are
prone to nut curculio (and pecan weevil) attack because of the protection
provided for overwintering sites. Insecticides applied for the control of
third-generation hickory shuckworm or pecan weevil also can reduce numbers
of nut curculio adults because their active periods coincide with these
pests.
George S. Smith and Maureen H.
O'Day
Department of Entomology, University of Missouri-Columbia
William Reid
Kansas State University
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Hickory Insects and Diseases
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