A reader recently asked us about the identification some “worms” that have made a home in her pecan tree. She wonders how to control the infestation without pesticides. The “worm” is fuzzy with black and white stripes. She said they move in clusters eating the leaves, then they move to the underside to molt, and finally they return to eat more leaves. She wrote the infestation has been getting worse each year.
Based on the description, we believe she is dealing with a walnut caterpillar infestation. These caterpillars (which are moth larvae) feed on the foliage of walnut, butternut, hickory, and pecan trees. Walnut caterpillars feed most heavily in early fall. The trees can usually stand 2-3 consecutive years of the caterpillars feeding before they die.
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If our reader wants to save her pecan trees from defoliation, there are several pesticide-free options she can try out. The first is rather daunting but can be quite successful if done correctly.
This option is to resort to manually removing the caterpillars. This includes walking around each tree in the evening (when they are in their nests) and brushing the caterpillars she sees into a bucket, examining the trunk as well. She can dispose of these in a different area. Also remove these creatures when they fall from branches.
The second option includes wrapping the trunk of the tree in burlap. The caterpillars will crawl under the fabric and it will be easy to remove many at once.
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Finally, she can consider introducing paper wasps to her garden. They tend to leave humans alone (as long as you don’t bother them), and they will feast on the caterpillars.
To conclude, our reader found a caterpillar population eating her pecan trees. We believe these are walnut caterpillars, and have provided some natural solutions to ease the infestation.