Spotting pesky pests

In Kansas we have two races of the fall webworm, each associated with different tree species. The blackheaded webworms are often seen in elm, mulberry, and osage orange trees; while walnut, pecan, flowering crab and sweetgums are often infested with the redheaded species. But either species will feed on almost any tree that isn't an evergreen. They particularly like isolated shade rather than trees surrounded by other trees.

Both races overwinter in woven silk cocoons mixed in soil and leaf debris. The blackheaded moths appear in May, about a month before the redheads. Eggs are deposited on the underside of leaves and began constructing their web immediately after hatching. They remain in this web through their entire feeding phase. As the food supply in the web is depleted, they expand their web to include more leaves and foliage.

Typically, in July, we start to notice the white webs on the end of the branches during the rapid growth and development. Once the larvae mature, they crawl to the ground to pupate in the litter on the ground.

Even though their timing is different, control is the same. SEQ CHAPTER \h \r 1 It would be best to control the first generation to reduce the second generation. However, the damage is normally insignificant during invasion of the first generation. Thereby, people go unconcerned at that time.

Begin scouting for the second generation fall webworm about mid July. Once the small worm hatches, they began to feed and enclose themselves in a web. Insecticides are only effective before the larva is enclosed in the web by most homeowner equipment. You must have enough pressure to penetrate the web after it is enclosed. That normally takes a high pressure sprayer or a commercial applicator.

Fortunately, webs from fall webworms are more of an aesthetic concern than a detriment or hindrance to the tree. Masses can also be removed by hand or by using a stick or broom handle or left alone if you don't mind the unsightly tree for awhile. Pruning or removing webbed branches is not recommended.

When black walnut, pecan or hickory tree leaves become "skeletons" and then disappear, walnut caterpillars were on the attack. Apple, birch, crabapple, elm, honeylocust, peach, maple, oak and willow trees can suffer the same fate, due to walnut caterpillars or their near look-alike relative, the yellow-necked caterpillar.

The parent moths of these hairy leaf eaters emerge in late spring and deposit egg clusters on tree leaves. The caterpillars that hatch may go unnoticed until they grow large enough that their eating starts to skeletonize leaves.

Walnut and yellow-necked caterpillars are gregarious; both species tend to congregate on the lower part of the tree -- sometimes gathering so closely that they create a mound or "knot" of wormy-looking wigglers. They molt there, leaving an ugly patch of hairy skins behind. After their final molt, the caterpillars crawl or drop to the ground, enter the soil, and pupate, like the webworms.

The caterpillars may reduce nut production, but will not damage the tree permanently unless it is already under tremendous amounts of stress. And like most insect pests, the earlier they are identified the easier they are to control, and the less damage they cause.

Editor's Note: Delta George is a K-State Research and Extension agriculture and 4-H extension agent assigned to Bourbon County. She may be reached at (620) 223-3720.