Nursery, Greenhouse, and Landscape News

Use of Entomophagous Nematodes Against Dogwood and Peachtree Borers

Dogwood and peach tree borers are common pests of woody landscape plants. Dogwood borers feed on a wide range of plants including dogwood, while peachtree borers feed on plants in the genus Prunus. Adults of both moth species fly and lay eggs for several months during the summer. After egg hatch, the larvae of both species chew through the tree bark and feed in the cambial layers. Dogwood borer feeds in the main trunk and limbs. Peachtree borer feeds on the main trunk near the soil line. Because chemical controls target the young larvae as they chew through the bark, applications of residual pesticides are required for effective chemical control.

Two recent studies indicate that the entomophagous nematode Steinernema carpocapsae (All strain) can control both of these pests as well or better than currently recommended broad spectrum pesticides. In both studies, nematodes were applied at a rate of 500 per square inch of bark surface when borers were in the larval stage. In the dogwood borer study materials were applied in late August, towards the end of the adult flight period. Applications resulted in significantly fewer infested trees compared to untreated controls. In the peachtree borer studies, applications were made in late April, prior to the first male flight of the year, resulting in a 66% reduction in borers on treated trees compared to untreated controls.

These studies suggest that commercially available nematodes have great potential for use in the urban landscape when high volume applications can be made and when temperatures are 55-85F. The moist environment where the larvae feed enhances the ability of these nematodes to enter and kill both dogwood and peachtree borer larvae.

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