Common name: Lilac borer
Scientific name: Podosesia syringae
Hosts: Lilac borer (Podosesia syringae) is also known as ash borer. This native insect attacks lilac (Syringa) and ash (Fraxinus), as well as privet (Ligustrum) and fringetree (Chionanthus)—all members of the olive family. Older plants and those under stress are particularly susceptible. The lilac borer, which is native to much of North America, can do extensive damage to host trees.
Damage
Lilac borer is damaging in the larval stage. The larvae bore into the stems and trunks of the host plant and produce long tunnels. They feed in the sapwood.
This damage can girdle branches, leading to dieback.
Areas where larvae have made holes and tunnels are swollen, with bark that is cracked and broken. Sap mixed with sawdust and excrement will ooze from the cracks.
Branches are often severely weakened and may break.
Life Cycle
Lilac borer overwinters as half-grown larvae in tunnels under the bark. The larvae pupate in spring. Adults begin to emerge in very late spring and continue through early summer.
The adult borer is a clear-winged moth that resembles a wasp. It is one inch long with a metallic, dark brown body. Yellow bands may be found across the abdomen.
Each female can lay between 300 and 400 eggs. The eggs are laid in the crevices of the bark.
They hatch into larvae with cream colored bodies and light brown heads. The newly hatched larvae enter the bark near the areas where they hatched out of the egg and begin to make tunnels.
The larvae begin feeding in the phloem (tissues that conduct food) and later move into the sapwood (which conducts water). As they mature, the larvae bore deeper into the sapwood of the tree.
There is one generation per year.
Management
Cultural Management
Trees and shrubs of low vigor, or in a weakened state of health, are especially susceptible to borer attack.
Prevention is the key in controlling wood-boring insect pests. Grow only trees and shrubs that are adapted to the area and site. Keep plants healthy and vigorous through proper planting, mulching, watering, fertilizing, pruning, and winter protection practices. Protect trees from injuries. Remove dead limbs or trees promptly to avoid infestations. Remove bark from felled trees if stored for firewood.
Biological Management
There are naturally occurring enemies of this native pest, primarily woodpeckers. They can help reduce borer populations, but will not always give complete protection.
Chemical Management
Systemic insecticides and trunk sprays are available to manage this pest.
The pesticide information presented in this publication is current with federal and state regulations. The user is responsible for determining that the intended use is consistent with the label of the product being used. The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement made by The Morton Arboretum.
For more information, contact The Morton Arboretum Plant Clinic at 630-719-2424 or plantclinic@mortonarb.org.