The peach tree borer is an insect pest that attacks peaches (Prunus persica) as well all other members of the Prunus genus, including cherries, plums, nectarines and apricots. Although trees can live through a borer attack, the insects can be fatal if they girdle the trunk of the tree. There is no specific peach tree variety known to be resistant to the peach tree borer, although trees grown on "Siberian C” and “Lovell” root stocks may be less hospitable to borers than others. Whenever possible, combine these root stocks with disease resistant varieties such as "Loring," "Veteran" and "Autumn Gold," all of which thrive in U.S. Department of Agriculture plant hardiness zones 8 through 11. It is important to prevent peach tree borer whenever possible and take action to treat any trees that are infected. When a tree cannot be saved, it should be promptly removed and destroyed to prevent further spread of the problem.
Borer Life Cycle
Adult peach tree borers are moths with clear wings frequently mistaken for wasps. Female borers lay their eggs at the base of the tree’s trunk in the spring, placing the eggs where the tree’s trunk and the soil meet. The larva hatch and tunnel into the trunk, climbing about 10 inches up to feed on the trunk’s sapwood. In the fall, the larva makes its way back down the tree’s trunk to overwinter in the tree, below the soil line. The next spring, the larva climbs back up the trunk where it again feeds before climbing back down the trunk to create a cocoon. About 2 weeks later, an adult peach tree borer emerges from the cocoon, ready to mate and start the cycle again.
If your tree has dying branches, drooping leaves and looks to be in overall poor health, check it for signs of peach tree borers. Look at the soil around the base of the tree for signs of larval activity. You may see the larva themselves, which are white, caterpillar-like creatures with brown heads that are about 1 inch long. Empty cocoons covered in a reddish-brown larva fecal material known as frass should also be present in the area where the trunk and soil meet. Dark, wet spots on the trunk of the tree that are oozing clear sap. Dig up some of the soil and check for signs in of infection just below the soil line as well as checking just above it. You may also notice the adult insects flying around the tree.
The first line of defense against peach tree borer is to grow healthy trees. The more healthy and vigorous the tree is, the more likely it is to survive a borer attack. Avoid using lawnmowers and motorized weed trimmers near the trunk of the tree, since they may cause damage to the bark, creating easy entry points for borers. Exiting damage is the most common reason for borer activity in established trees. Apply pesticide, such as permethrin, to the trunks of trees annually, thoroughly wetting the trunk during application. Avoid applying the pesticide close to harvest: many pesticides recommend discontinuing use 14 to 21 days before harvest. Pheromone traps can be used to indicate the proper timing of insecticide application. Pesticide should be applied when male borers are attracted to and caught in the traps. Synthetic hormones can also be used to control borers by over-stimulating the males, desensitizing them to the female pheromones and making it more difficult to find females.
It can be difficult to evict borers from your peach tree once established because many pesticide sprays do not reach insects below the bark. One option for infected trees is to purchase the Steinemema carpocapsae parasitic nematodes from your garden center. These nematodes are small roundworms and are parasites of peach tree borers. The nematodes are injected into the tree along with distilled water and will kill the larva living in the tree. It is also possible to carefully remove 4 or 5 inches of soil from around the tree and look for larva and their tunnels. Once the larva has been located, pierce it with a sharp wire or knife. Although this method does kill the borers, it may also cause more damage to the tree and should be used only with caution.
- Clemson University Cooperative Extension Service: Peach Insect Pests
- Arizona Cooperative Extension: Peach Tree Borers
- Texas AgriLife Extension Service: Lesser Peachtree Borer
- Colorado State University Extension: Peach Tree Borer
- ArborCare/ArbborScape: (Peach Tree Borers)
- Utah State University Cooperative Extension: Greater Peachtree Borer
- The University of Kentucky: Peachtree Borer
- Home Orchard Society, Inc.: The Practice of Grafting
- University of California Cooperative Extension: Varieties for Planting in the Home Garden
- Comstock/Comstock/Getty Images