   Peach Tree Borers - April 6, 2011 Jeff Schalau, Associate Agent, Agriculture & Natural Resources University of Arizona Cooperative Extension, Yavapai County While pruning my peach tree last week, I found some trunk damage at the soil level. After inspecting it more closely, I saw evidence of last summer’s peach tree borer activity. This tree has been colonized by peach tree borers for the last several years. Unfortunately, once they start on a tree, it becomes weakened and is often re-colonized in subsequent years. Peach tree borers are native insects that would normally colonize native Prunus species. Commercial and backyard orchards having peach, nectarine, plum, cherry, apricot and almond trees are susceptible. Now is the time to inspect your trees for damage and apply one of the treatments outlined below. Adult peach tree borers (Synanthedon exitiosa) are steel blue to black moths with transparent wings that emerge in the late spring and early summer. They often have an orange band on their abdomen and this causes them to resemble a wasp. Females lay their eggs during summer, usually starting in June through August, on the bark at the base of tree trunks. After hatching, the larvae tunnel into the sapwood of the tree at or slightly below ground level. The larvae (caterpillars) are light brown or pinkish with a slightly darker head. Larvae feed under the bark through the summer, and move down the trunk as cold weather approaches. The partially grown larvae resume feeding in the spring. Pupation takes place under the bark, and lasts about two weeks. Moths begin to emerge in late spring, at which time mating takes place and the cycle repeats. Their feeding girdles the tree, disrupting the flow of water and nutrients in the xylem and organic compounds in the phloem. To inspect your fruit trees for peach tree borers, begin by looking for reddish-brown frass (larva fecal material) around the base of the trees. You may also see globs of sap exuding from the base of the tree. These signs indicate a larval entry point. Infested trees may also appear to be stressed (droopy leaves and dying branches). In some cases, you may need to excavate some soil at the base of the tree to see the entry points. Egg laying on older trees is usually concentrated around existing wounds. Control of existing peach tree borer infestations can help reduce future problems. Avoid damaging the bark when cultivating around trees. White paint applied to the bark around the base of the trees can help seal cracks in the bark which the female moth uses for egg laying. Individual larvae may be dug out of trees with a clean knife and wire (a paper clip). Inserting the wire into a gallery may be sufficient to kill larvae. Be careful to not injure the tree, as the damage may be as severe as that inflicted by a borer larva. This treatment is an appropriate control strategy for backyard trees. Insecticide applications can be effective at controlling the early larval stages. Peach tree borers can be controlled by insecticides that contain carbaryl, permethrin or esfenvalerate. These insecticides are available in some garden centers and on-line (read the label to ensure the product is labeled for edible fruit). In older references, naphthalene crystals (mothballs or moth crystals) are often listed as a chemical control. Since naphthalene crystals are not labeled for this use, it is no longer a recommended practice due to environmental concerns. An environmentally-friendly method of peach tree borer control uses the insect parasitic nematode Steinernema carpocapsae. Nematodes are tiny roundworms. This species parasitizes the peach tree borer larvae. Nematode applications are most effective when larvae are feeding actively and tunnel openings are largest in late summer. The nematodes are applied with a squeeze bottle in suspension with water. The best preventative treatment for any pest species is proper care. You simply maintain the highest level of thrift and vigor in your orchard. Fertilize, water, avoid sunscald, prune, control weeds, and lastly, observe the trees for early signs of pest infestations. Follow the Backyard Gardener on Twitter – use the link on the BYG website (see link below). If you have other gardening questions, call the Master Gardener line in the Camp Verde office at 554-8999 Ext. 3 or e-mail us at cottonwoodmg@yahoo.com and be sure to include your name, address and phone number. Find past Backyard Gardener columns or provide feedback at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/.  |