June 26, 2010

1 - Peach tree borers can injure any of the stone fruit trees.

Yard and Garden - June 26, 2010


My apricot tree is dying. This is a wonderful tree that grew from a pit to provide shade for my patio and home. I do not want this tree to die. What can I do?

- Ms. Y.

Telephone conversation


When we hear that an apricot tree, peach tree, cherry tree, or any of the other stone fruit trees is struggling, we begin to consider the peach tree borer as a causal agent. Of course, we have to rule out insufficient irrigation. The peach tree borers are the larvae (caterpillars) of a day-flying moth that looks somewhat like a wasp. The moth lays eggs on the bark near the base of a stone fruit tree. These larvae then bore under the bark and can girdle the tree. Young trees with a slender trunk are more quickly injured while older, larger trees can tolerate the borers more readily.

A symptom of the peach tree borer is the presence of a jelly-like mass of sap at the base of the tree. This sap may have sawdust (boring dust) mixed into it and, if it is dry, can be very hard. Ms. Y agreed that the jelly-like sap had accumulated around the base of the tree, confirming that the peach tree borer was the likely culprit.

Treatment is difficult because the hardened sap protects the larvae as it is feeding under the bark. Some writers recommend removing the sap from the base of the tree (moisten it first so that it can be easily removed), finding the tunnels made by the boring larva and inserting a flexible piece of wire into the tunnel with the intention of impaling the larva. If you can reach the larva with the wire, this can be effective, but it is not always possible. Do not dig into the bark with a knife or other implement looking for the larva. You can do more harm to the tree than the borer.

Research has shown some effectiveness of parasitic nematodes (extremely small round worms that feed on larvae). The most effective parasitic nematode was determined to be Steinernema carpocapsae. This biological control agent is available by mail from some insectaries.

Spinosad insecticide has also shown to be effective. This toxin is produced by a bacterium and is a natural toxin that can kill the borers.

When using parasitic nematodes or spinosad, moisten the base of the tree and remove the sap nodules so that the treatment can have closer contact with the borers.

To confirm peach tree borer and determine the best treatment method in your circumstances, contact your local NMSU Cooperative Extension Service office or Extension Service Master Gardeners.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.


For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook page.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!