Borers are the larvae of certain moths and beetles that feed on the wood in trees instead of the leaves or fruits. Borers tunnel into the woody parts of trees, including the trunk, twigs, branches and even the roots. Borer infestations in fruit trees are difficult to control, and insecticidal sprays are only effective during limited times of the borer's life cycle. Several other methods exist, however, to control borer infestations in fruit trees.
Look for signs and symptoms of a borer infestation. Study the fruit trees for tunnels that larvae have made in the trunk and limbs. Also look for dying branches.
Apply an insecticidal spray to the fruit trees once per month in the summer, following the application directions on the label. Use the insecticide only when the adult borers are active and laying eggs. The timing of insecticide use is crucial, because the insecticides won't work on borer larvae, only on the adults and eggs.
Introduce biological controls to eradicate the borers. Trichogramma are small wasps that are parasites to more than 200 moth species, including borers. The wasps lay their eggs inside the borer eggs, and the developing Trichogramma feeds on the borer larvae.
Wrap the tree trunks with burlap or three layers of old newspapers. Wrap the fruit trees before the adult borers begin to emerge in the springtime. Make sure that you cover the tree from the ground to the lower branches and leave it on the tree for the first one or two seasons. Wrap any nearby young trees, even if they're not infested, to prevent the adult borers from laying eggs on the bark.
Hand-worm the trees by digging the larvae out of their holes in the tree trunk and branches using a wire or knife. Look for the larvae in August and September. The larvae will be easier to find during this time, because the newly hatched larvae will cause sap to flow when they begin to feed. Seal the holes with tree paint immediately after removing the larvae.
Keep the fruit trees healthy and injury-free. Fertilize the fruit trees with an appropriate all-purpose granular fertilizer once per month to boost the trees' strength. Water the trees once per week. If the tree is weakened by any other diseases, be sure to treat those as well.