Ash/Lilac borers overwinter as larvae in the stems of lilac and sometimes privet. The borers cause the stems to die. The borers also attack Ash trees by boring into the tree trunks and destroying the cambium layer causing the tree to die.
The adult moth emerges in mid to late April, peaks in May, dwindles by mid to late June and ends by the first week in July. The moth has clear wings and resembles a wasp in appearance. There is one generation per year.
It is best to use a pheromone trap to determine the presence of the adults. Initiate spray treatments seven to 10 days after the first moths are captured. If phermone traps are not used, make three applications of an insecticide at 14-day intervals. Chemicals that can be used are Dursban, Thiodan or Lindane. Treat the trunk and larger limbs of ash or the lower portions of the stems of lilac and privet.
As trees and shrubs begin to leaf out in the spring Eastern tent caterpillar larvae begin to hatch. The larvae produce a small ``silken tent'' in the crotch of a branch. Within the tent, the gregarious larvae rest as well as escape adverse elements.
Larvae leave the tent to forage on newly emerging and emerged foliage and return to the tent when not feeding. After the larvae have completed their feeding which is usually in mid-May some may remain in the tent where they spin a cocoon in which to pupate.
Most larvae spin their cocoon under debris on the ground. In two to four weeks, the adults emerge from the pupa stage, mate and deposit eggs for next year's generation. There is only one generation per year.
Tent caterpillars can be controlled by using a contact insecticide such as Orthene, Dursban, Malathion or Sevin. The chemical will not penetrate the web so break open the web before spraying the larvae. Also, spray the foliage on the tree. The insects will be destroyed by ingesting the chemical.
-- Dennis Bejot is director of K-State Research and Extension-Douglas County. For questions about gardening call Extension's Master Gardener Hotline, between 1 p.m. and 4 p.m. Monday through Friday, 843-7058.