The peach tree borer is the larva of a type of moth. The larvae are pink or light brown with a darker head and hatch from eggs laid by the female moth near the base of stone fruit trees, such as peaches and nectarines. The larvae hatch, then burrow into the crown and lower trunk of the tree. If the damage is significant enough, the peach tree borer can completely girdle a tree, killing it.
Remove 6 to 8 inches of soil around the base of the trunk of a tree. Peel back the bark where peach tree borers are suspected, using a pocket knife. Examine the underlying tissue for the burrows the larvae have made.
Follow each burrow found until the peach tree borer is located. Remove the larvae from the tree and destroy it.
Be careful not to do too much cutting on the tree, as excessive damage done by looking for borers may also threaten the tree.
Use a pheromone-type moth trap to identify when peach tree borer moths are active.
Treat trunks in late spring, using Carbaryl spray insecticide, which is commercially available as Sevin. Ensure the type of Carbaryl used is specifically formulated for use on trunks and branches. Timing is critical. The spray must kill the moths before they have a chance to lay eggs.
Remove extra soil, tree suckers, and weeds from around the base of the plant. Apply the spray to entire trunk and lower limbs of the tree, until it starts to puddle around the base of the tree.
Keep Carbaryl spray off foliage to avoid killing beneficial insects. Do not irrigate directly on trunks or lower branches to avoid washing the spray off the tree.
Use Parasitic Nematodes
Purchase Steinemema carpocapsae nematodes, which will actively attack and kill peach tree borer larvae, from a reputable resource. Mix the nematodes with distilled water at the rate of 1 million worms to to one ounce of water. Place the mixture into a squeeze bottle with a long piece of plastic tubing attached.
Inspect the trunk for peach tree borer activity. Look for holes that have sawdust-like frass at their entrances. Insert the tubing into these holes created by the borers. Inject the liquid mixture into each hole until it flows out of the hole. Mark the holes for future inspection.
Examine the holes one week later, to see if more frass is visible. If so, retreat with more nematodes.
Store the nematodes in a cool dry place. Ensure the nematodes are not exposed to sunlight, as this will kill them.