Pecan Weevils

Pecan weevil larvae. Photo courtesy of USDA Cooperative Extension Slide Series, Bugwood.org.

Pecan weevils are one of the most serious pecan pests for the home owner.  If you have ever opened a pecan to find a small white worm inside it, you have seen the larva of the pecan weevil.  The adult pecan weevil is a light-brown or grayish beetle with a long beak.  The beak of the female is longer than the body.

The adult weevils emerge from the soil from August through September, frequently after rains of 1 inch or more.  Adult pecan weevils feed on green nuts causing some green nuts to drop.  The more serious damage is caused by female pecan weevils drill holes in nuts and lay eggs.   The resulting larva feed within the nut.  After the pecans fall to the ground and the larva chews their way out of the shell and burrow into the soil.  They will remain in the soil for 1 or 2 years before emerging as adults to continue the cycle. 

Since the lifecycle of pecan weevils can span three years, control requires consistent treatment.  Good orchard sanitation and judicious spraying will help control this pest.  First, promptly sweep up fallen pecans from under the tree each fall and dispose of them.  This will help remove pecan weevil larva from the area underneath the tree. 

Secondly, consider spraying the root zone and trunk of the tree with an insecticide such as carbaryl when the adult beetles are emerging from the soil and moving into the tree canopy.  Start monitoring the beginning of August and spray when adult weevils are found.  Continue to monitor and treat as needed through September.  

Adult pecan weevil.  Photo courtesy of USDA Cooperative Extension Slide Series, Bugwood.org.

An easy way to monitor for pecan weevils is to wrap a burlap bag around the base of your tree several feet off the ground.  Adult weevils crawling up the trunk will be trapped under the burlap.  Daily monitoring will allow you to target your spray when the weevils are most active and it will provide a limited amount of physical control.  If you are handy, you can find information about building more intricate pecan weevil monitoring traps here:  http://pecankernel.tamu.edu/insect_update/weeviltraps.html