With this year’s hot dry summer, you can expect insect and disease problems to increase. It is common for insects to attack stressed plants. For trees, the webworm problems are more of an issue in hot, dry summers. In addition, over the past few days we have seen an increase in webworm activity in many landscapes.
Webworms form a webbed nest on tree limbs starting in mid-summer. An adult worm lays eggs on the underneath side of leaves. The eggs hatch within 7-10 days and a progressively enlarging web forms over limbs within 14 days. Typically, there are 2 or 3 generations of webworm per year with the heaviest population in the fall. Webworm will infest over 100 species of trees with the most common in Oklahoma being Pecan, Walnut, Elm, fruit trees, Maples, Sweet Gum, Cottonwood, and Willow.
Webworm is mostly an aesthetic problem since most trees usually survive and recover without permanent injury. However, heavy and persistent infestations may cause limb and branch dieback.
Early mechanical control by pruning out the small nest is the best management practice. The nest should be removed from the site or completely crushed. During early stages of the web development, bacillus thurngiensis (BT) is a safe and effective control. Stronger insecticides are required for control as the webs mature. When spraying for webworm, it is important that the spray is applied with sufficient pressure to penetrate the web.
Control during the first generation of webworm is important, as it will limit second and third populations and damage. The old practice of burning the webs should not be used as this causes more permanent damage to the tree than the insect itself.
Remember, one of the best defenses for disease and insects is to have healthy, vibrant, and growing plant material regardless of the current environmental conditions. Therefore, during the heat and drought, make sure your landscape is receiving at least 1 1/2 “of water each week.
Take time to inspect your trees frequently for webworm and if you see an outbreak, contact WesternLawns at 405.943.4242.