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| 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.
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| 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
