Cutworms make early appearance

Shackelford County extension agent Michaela Bradford said that large numbers of mesquite cutworms have been seen recently. 

“It is time to spray for mesquite cutworms in shade trees,” she said.

The cutworms are typically pruning leaves off of mesquite trees in this area in mid to late July, but seem to be out a little earlier this year.

“The mesquite cutworm is actually a caterpillar that turns into a plain colored moth after it runs its cycle,” said Bradford. “The eggs are laid by the moth and the hatched caterpillars feed on mesquite foliage.”

Excessive leaf loss can cause a sickly look to the affected mesquite trees.

“After defoliating all or part of a tree, the larvae burrow into the soil and pupate into moths later on in the fall,” continued Bradford. “Although mesquite cutworms are present each year, some years the numbers are higher due to climate conditions.”

Former county agent Rocky Vinson told Bradford that he recently sprayed his trees and “saw thousands of them.”

Temperatures that are above the season average can cause an earlier-than-usual emergence of insects according to Texas A&M AgriLife Extension Service entomologist Dr. Charles Allen.

People looking for mesquite cutworms need to know that they feed on the tree leaves at night.

“If you are looking for mesquite cutworms during the day, you will find them in the litter at the base of the tree,” said Bradford. “They will also hide under anything that is around the tree as well as under coarse bark and cracks in the soil.”

The caterpillars are dark green with stripes down the length of the body, according to the Texas Agrilife website. The worm droppings will appear as tiny green pellets.

“The cutworms will not kill the tree, but they obviously cause a loss of valuable summer shade in yard trees,” said Bradford. “If you want to control mesquite cutworms in shade trees, a two-step approach is recommended.”

First, sprinkle a band of insecticidal dust around the base of the tree. 

“Dusts containing permethrin or sevin will work,” said the county agent. “This application will kill many of the worms that are in the litter at the base of the tree and will create an insecticide barrier to worms moving to the tree.”

People can also treat the trunk of the tree, since the caterpillars travel on it each day, according to Texas Agrilife.

“Second, spray the tree late in the evening with a liquid insecticide such as permethrin, malathion or sevin,” Bradford said. “Caterpillar sprays containing spinosad or bacillus thuringiensis are also environmentally friendly choices.”  

Mesquite cutworms can also have a major impact on rangeland management. 

“Those who are planning to kill mesquite trees by applying chemical spray on rangeland are encouraged not to spray when there is major defoliation of many trees,” the county agent added. “The chemicals that kill mesquite must be absorbed by the leaves in order to work. Spraying defoliated mesquite will yield little or no root kill.”