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Problem: Ash/lilac Borer - Podosesia syringae
Hosts: Lilac, ash, mountain ash, and occasionally privet.
Description: Lilac: Canes or stems wilt suddenly. The base of infested stems are swollen and the bark separates from the wood. A fine sawdust-like material is present around holes in the canes. Ash: Trunk and portions of the major branches show exit holes of insects. Sawdust may accumulate under the tree.
Ash/lilac borers overwinter as larvae in infested trees and shrubs. Pupation occurs in the spring. Moth emergence generally begins in mid- to late-April, peaks in May, dwindles by mid- to late-June and ends by the first week of July. The moth has clear wings and resembles a wasp in appearance. It is about 1" long and has a wing span of about 1½ inches. Moths deposit eggs in cracks and crevices of bark. They hatch in 10 to 14 days. Larvae immediately bore into wood. Frass accumulates around holes. Swelling and cracking of the bark are associated with repeated infestations and branches may be severely weakened at the feeding sites. During dry periods in late summer, terminal shoots of infested plants wilt. There is one generation per year.
Recommendations: It is best to use pheromone traps to
determine the presence of the adults, which are clearwing moths. Initiate spray treatments
seven to 10 days after the capture of the first moths in nearby pheromone traps. If you
don't have pheromone traps, make three applications at 14-day
intervals starting in mid-May. Thoroughly treat the trunk and larger limbs of ash
or the lower portion of the stems of lilac or privet. Heavily infested ash should be cut
and burned during the fall and winter periods. Infested stems of lilac or
privet should be removed as well. Homeowner products for control includes
permethrin. However, many permethrin products are not labeled for
ash/lilac borers. One that does is Hi-Yield Garden, Pet & Livestock
Insect Control.
References:
1. Insects and Mites Associated With Shade Trees and Woody Ornamentals, pg 17, K-State Research and Extension Pub S-85
2. Insects That Feed on Trees and Shrubs, Cornell University Press, pg 224
3. Life Histories of Common Insects, Mites and Nematodes Infesting Ornamental Plants in Missouri, Missouri Department of Agriculture, pg G-12
4. Lilac Borer, Virginia Cooperative Extension, Lilac Borer Factsheet
Last Update: 08/15/2003
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