Look Up...Do you see Fall Webworms in Your Trees?
September 21, 2016
It’s that time of year again! The time when temperatures begin to cool, humidity increases and plant pests come out in force. Trees that are already stressed by extreme weather conditions this year, such as spring flooding, resulting nutrient deficiencies and a hot and dry summer, are particularly vulnerable to pests. One such pest that will be showing up en masse is the fall webworm.
Beginning in late July and early August, the fall webworm begins to rear its ugly head in the DFW area. Pecan, sweetgum, mulberry, willow, hickory, oak and a plethora of other tree species are often their primary targets. You’ll find webworms in clusters, surrounding themselves with webs that can cover large swaths of tree foliage. These webs can reach several feet across in diameter and hundreds of caterpillars.
The fall webworm, or Hyphantria cunea, eventually morphs into a pretty, bright white moth with dark brown spots on the wings and a soft, furry body. In spring, they lay their eggs in the crevices of trees. They are hairy creatures roughly one-inch long with pale yellow or green bodies and a stripe of dark brown or black down their center. Black bumps run from their tail to their red-colored heads, while the entire body is covered in fuzzy, long hairs.
How do they damage trees?
Fall webworms are hungry critters and they can make their way through a lot of your tree’s foliage in a short amount of time. They use their sharp mouthparts to quickly chew and consume leaves. They’ll start with the most fresh and tender foliage and work their way through your tree. They can quickly defoliate large sections of your tree, putting it under a lot of stress. Webworms can have up to four generations each year; some areas of Texas will experience webworm outbreaks in spring and early summer, in addition to the fall season. But, it’s the fall generation that tends to cause the most damage to our trees.
In winter, we apply natural dormant oil to trees. Dormant oil suffocates the insects that overwinter in the cracks and crevices of your trees, keeping them from hatching in spring, only to reproduce through the year, and causing an even bigger infestation. If you missed out on your application of dormant oil last December or January, scheduling a time for this winter would treat not only webworms, but also aphids, leafhoppers, leafrollers, mealybugs, mites and scale shrubs and trees such as Hollies, Red Oak, Live Oak, Pecan or Maples.
Didn’t apply dormant oil? No problem! We can also treat for webworms now using natural biological controls. If you have webworms in trees, we suggest treating trees quickly. Trees that are already stressed from drought, heat, disease or nutrient deficiencies will experience more damage from a caterpillar infestation and can have a harder time recovering.