Systemic insecticides, whether applied as injections or as soil treatments, generally have not given reliable control of clearwing borers. The trunk and main scaffold limbs should be sprayed to runoff but the foliage need not be sprayed. All of those products are contact insecticides that require proper timing in order to intercept newly hatched clearwing borer as they crawl over or tunnel into the bark. Chlorpyrifos (Dursban® 50W) can still be used in commercial nurseries. Chlorantraniliprole (Acelepryn), is an effective, bee-friendly option. Pyrethroids including bifenthrin (Onyx®, (Talstar®) and permethrin (Astro®) work well. Properly-timed bark sprays with contact insecticides can prevent infestation of susceptible trees and shrubs. Coarse, sawdust-like frass exuding from cracks in the bark from clearwing borer. Symptoms of clearwing borer infestation include crown diebackįigure 1b. Feeding holes left by woodpeckers or other birds may indicate that a tree is infested.įigure 1a. When the adult moth emerges, it leaves an empty, tan shell (pupal skin) that protrudes from the bark. In some hosts, especially Prunus species, the frass may be mixed with oozing sap or gum. Established trees may persist in poor condition and be re-infested year after year.Ĭlearwing borers expel coarse, brown frass (sawdust-like fecal material) from cracks in the bark. Large limbs may die or become so weakened that they are easily broken in the wind. Infestation sites often are marked by cankers, calluses, or cracked bark. Detecting Clearwing BorersĮarly signs of clearwing borer infestation are wilting of terminal shoots, and branch and crown dieback. The most damaging clearwing borers are associated with dogwood, lilac, ash, oak, rhododendron, and ornamental Prunus species, including flowering peach, plums, and cherries. The larvae are whitish, hairless caterpillars with brown heads. The moths feed only on nectar or not at all so they do not cause damage. Clearwing BorersĪdult clearwing borers are delicate, day-flying moths that resemble small wasps. It is important to know when the adults of each species are active and which plants are vulnerable in order for treatment to be effective. While some are attracted to a range of hosts, most attack only certain kinds of trees and shrubs. Several species of clearwing and flatheaded borers can infest landscape plants. Once inside the tree, borer larvae are no longer vulnerable to insecticide sprays and are seldom detected until serious damage has been done. The young larvae quickly tunnel beneath the bark where they feed and grow. Hatching occurs about 10 days to 2 weeks later. After mating, the females fly to a suitable host and lay eggs on the bark, often in crevices or around wounds. Adults may locate suitable egg-laying sites by responding to volatile chemicals that emanate from stressed trees.Īdult borers emerge from infested trees in the spring or summer. However, when trees or shrubs are transplanted into the landscape, stresses such as drought, soil compaction, sun scald, or injuries can weaken them and make them more susceptible to attack. Infestation and Damageīorers rarely infest healthy plants growing in their natural environments. The keys to controlling these pests are to keep plants healthy and, if necessary, to treat during those times of the year when the insects are vulnerable to insecticides. The groups differ somewhat in their habits and host preferences, which can affect the approach for controlling them with insecticides. ![]() Infestation sites also provide entry points for plant pathogens.Ĭlearwing and flatheaded borers are the main types that attack woody ornamentals. This causes girdling, branch dieback, structural weakness, and decline and eventual death of susceptible plants. They tunnel and feed under the bark in living wood, destroying water- and sap-conducting tissues. Most borers are the larvae (immature stages) of certain moths and beetles. ![]() Wood-boring insects are among the most destructive pests of ornamental trees and shrubs. University of Kentucky College of Agriculture ENT-43: Insect Borers of Trees and Shrubs | Download PDF by Daniel A.
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