   Peach Tree Borers - October 22, 2003 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Fruit trees require year-round care to keep them healthy. During fall, you should pick up the mummies (rotten fruit carcasses), start planning your fall application of dormant oil sprays, and get out and check peach, plum, apricot, cherry, and almond trees for peach tree borers. Peach tree borers are common in our area and can weaken and even kill stone fruit trees. Adult peach tree borers (Synanthedon exitiosa) are steel blue to black moths with transparent wings that emerge in the late spring and early summer. Females lay their eggs during summer on the bark at the base of tree trunks. After hatching, the larvae tunnel into the tree at or slightly below ground level. The larvae are light brown or pinkish with a slightly darker head. They feed just under the bark in the root crown area and may burrow up into the tree. This 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 also appear weakened (droopy leaves and dying branches). In some cases, you may need to excavate some soil at the base of the tree to find the entry points. I dig around and feel for hardened clods of soil held together by exuded sap. Backyard orchards can be treated by manually "worming" the trees. Simply find the entry point and use a pocket knife to dig the larva out. Use some discretion here. You can seriously injure the tree if too much wood and bark is removed. A major advantage of this approach is that you always know that the pest is dead. For large orchards, insecticide applications can be effective at controlling the early larval stages of peach tree borer. Here, timing is critical and the manager should explicitly follow label directions. In the old days, treatments called for the use of naphthalene crystals (mothballs or moth crystals). This is no longer a recommended practice. Another method of peach tree borer control uses an insect parasitic nematode, Steinernema carpocapsae. Nematodes are tiny, eel-like roundworms. This species parasitizes peach tree borer (and other soil borne insect larvae) 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 suspension of distilled water. To apply, clear the tunnel entrance of frass, then insert the nozzle applicator as far as possible into the gallery (tunnel). Inject the suspension until the gallery is filled, then plug the tunnel entrance with rope putty or grafting wax. You must agitate the applicator to keep the nematodes suspended in the solution. One week after application, check that each gallery is still plugged. Retreat any that are unplugged and cover the opening again. The best 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. An integrated pest management approach promotes beneficial organisms and has a little or no effect on non-target species. So, go out and look at the base of your fruit trees, treat them if necessary, and enjoy the fall season. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at mgardener@verdeonline.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://ag.arizona.edu/yavapai/anr/hort/byg/. |