The peach tree crown borer (Synanthedon exitiosa) threatens a wide variety of fruit trees. The insect pest occurs on plum, cherry, apricot and other stone fruit trees. Native to the United States, the peach tree crown borer occurs also in Canada. The adult moths have a wasp-like appearance with a metallic blue coloration on their fore and hind wings. The abdomen has a yellow banding. The male peach tree crown borer is slightly more slender than the female.
Beginning in mid-June and continuing until September, the adult peach tree crown borer lays eggs. Each female has the capability of laying 500 to 1,200 eggs, according to Oklahoma State University. The eggs are laid on the lower 6 inches of the fruit tree's trunk or in the soil surrounding the trunk. The eggs hatch 10 days after being laid. Only one generation of the insects occurs per year.
The larvae begin to feed on the fruit tree wood. They bore into the trunk of the tree at the base and along the larger roots. The larvae grow to approximately 1/4 inch in diameter. Small trees can easily be completely girdled by the feeding frenzy of the larvae and quickly die if control is not gained. In areas of the tree that are affected by the larvae, the tree begins to ooze a gummy substance as it tries to get rid of the larvae naturally but is unsuccessful.
Seasons of the Larvae
The larvae will continue to feed throughout the warm summer weather. When winter arrives, they will leave the tree and burrow into the soil surrounding the tree's root system. When the soil begins to warm up in the spring, the larvae return again to the tree to consume more sapwood. From May to June the larvae finally finish feeding on the tree and pupate They weave a cocoon of silk and wood fibers around themselves below the soil surface, according to Colorado State University. The larvae will remain in a pupal stage for one month before emerging as adults.
Insecticidal sprays do not kill the larvae once they are safely in the sapwood of the tree, which makes control difficult. Insecticides that contain permethrin, esfenvalerate or carbaryl can offer hope of control if applied during the egg-laying stage of the insect's life cycle. Laying down paradichlorobenzene moth crystals around the base of the tree can help control a few of the larvae but will not kill them all. The crystals should not touch the trunk of the tree and they can damage surrounding plant life. The crystals work best in warm weather--above 60 degrees F--because they release gas that can kill the larvae, according to Colorado State University.
Tree Care Considerations
Older fruit trees can often survive a peach tree borer infestation if it is good health. Maintaining a regular fertilizing and watering schedule can help the tree stay healthy. Avoid wounding the base of the tree's trunk where the borers often attack. The borer larvae will often utilize wounds sustained through overcultivation to gain easy access to a healthy tree's sapwood.