Several species of borers attack apple trees. Borers may affect other fruit-bearing plants aside from apple trees such as pear and peach trees. Home fruit growers should be aware of the types of apple fruit borers in order to identify if their apple trees are suffering from infestations and to control or eradicate these pests.
Flatheaded Apple Tree Borer
Adult flatheaded apple tree borers measure about a 1/2 inch long and are dark brown color with a metallic luster. These sun-loving insects are active in June and July. You may find adults as early as May on the sunny sides of trees where females lay eggs inside the bark's crevices. The egg-laying continues from June to September. The larvae have broad, flattened head ends and cylindrical bodies; they bore into the wood, leaving tunnels that appear oval in cross-section. A powdery frass (excrement) fills the tunnel as the larva feeds. In the fall, the larvae bore deeper into the wood, where they shelter during the winter and pupate the following spring. There is only one generation of flathead apple tree borers per year.
Wrapping newly planted trees' trunks with burlap or old newspapers before the adults start to emerge in the spring can help prevent egg-laying. Removing larvae with a sharp knife may also help, especially when there are heavy infestations. Promptly paint the wound after removing the larvae. Applying insecticides such as carbaryl, permethrin and imidacloprid monthly over the course of summer is necessary because of adult emergence and egg laying that can occur over a long period.
Roundheaded Apple Tree Borer
The roundheaded apple tree borer attacks apple, pear, quince, mountain-ash, hawthorn and serviceberry. It emerges in the fall measuring up to 1 inch long. The body is white with three broad, brown, longitudinal stripes that extend the entire length of the body. Most egg-laying occurs from late June to early August. When eggs turn into larvae, tunneling occurs about 4 inches below ground up to 1 to 2 feet above the ground.
Suspect roundheaded apple tree borers to be present when pigtail-shaped frass and wood cuttings on the bark or at the base of the tree appear. Brushing paint or wrapping a loose-fitting barrier around the lower trunk will prevent egg-laying or damage. Dig larvae from bark with a sharp knife. Spray insecticide such carbaryl, permethrin and imidacloprid to help control infestation.
The codling moth is a notorious apple pest that feeds on apples, pear, quince, peach, plum and cherry. In the fall, male and female adults appear, measuring about a 1/2 inch long. They are grayish and striped with chocolate brown patches at the base of their wings and copper-colored scales inside the wing tip. The female codling moth lays white, flattened, pancake-shaped eggs singly on leaves.
The larva has a brown head and a 3/4-inch pinkish white body. Larvae cause wormy apples and apple stings. They burrow into fruit at the calyx or through the side of the apple. They feed on the flesh just beneath the skin's surface, then burrow directly to the center of the fruit and feed on the seeds.
Apply insecticide when eggs begin to hatch. Removal of unsprayed host trees within 50 meters of the orchard will reduce codling moth immigration.