An outbreak of Walnut Caterpillars has invaded Fort Bend County and is targeting the local pecan tree foliage. The caterpillars are approaching their third generation this month after causing devastating defoliation in June, according to the Fort Bend County Texas A&M AgriLife Extension Service.

Gary Gillen, owner and president of Gillen Pest Control in Richmond, said this is the worst Walnut Caterpillar outbreak he has seen.

"It's considered an epidemic," he said. "They can completely defoliate a tree. They are very aggressive and very fast. As soon as you see them working on your tree, you need to take action quickly."

The second generation of caterpillars caused severe damage, and the third generation will infest a much larger area and may move into local commercial orchards, according to the A&M Extension Service.

The Walnut Caterpillar feeds off pecans, hickories and walnuts with the population stemming from female moths laying between 300 to 900 eggs within the foliage. Eggs will mature in about 10 to 12 days with larval feeding lasting 23 days before seeking other tree sites.

"This would be the time to treat," said Bill Ree, pecan pest management specialist with Texas A&M AgriLife Extension. "Without blindly spraying for them, we ask individuals to scout for new populations. If you see the new egg masses on mature foliage, it should be about a week before the larvae hatch out."

Gillen said a large hot spot of the outbreak is along FM 359 north of Richmond. Throughout the month of June, Gillen said his company handled hundreds of calls regarding the infestation.

Although this is the largest outbreak Fort Bend County has seen in the last five years, the process starts a year or two prior to infestation. Gillen said the caterpillars usually appear two to three years in a row as the caterpillars seen come from the moths who laid their eggs the year prior.

To combat the infestation, Gillen and the A&M Extension Service urge citizens to act quickly and treat foliage as soon as Walnut Caterpillars are spotted. Recommended products for homeowners include Dipel, Thuricide, Caterpillar killer and products with spinosad, such as Green Light Law and Garden with Spinosad. Homeowners may also spray clusters with dish soap and water.

"If you get these insects, to avoid as much damage as possible, act quickly," Gillen said.