   Forest Health - May 8, 2002 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Current drought conditions have really brought out the forest pests and unfortunately, these pests don't know the difference between small private ownerships and the larger Federal and State Trust lands. Yavapai County Cooperative Extension has been fielding many calls about bark beetles: especially in the Prescott and Sedona areas. In the Prescott area, Ips species are attacking Ponderosa pines. In the Sedona area, cypress bark beetles are affecting Arizona and Leyland cypresses. Drought years like this keep a County Agent busy. Cypress bark beetles (Phloeosinus spp.) are native to Arizona across the natural range of Arizona cypress. Cypress bark beetles seem to have expanded their range since this Arizona and Leyland cypress have become important landscape/windbreak plants across the state. The first signs of infestation are dead branch tips caused by the beetle boring into the small twigs. The dead tips often remain hanging on the tree (this is referred to as "flagging"). The dead branch tips eventually fall off and this level of beetle activity can be viewed as natural pruning of an otherwise healthy plant. Healthy trees can tolerate flagging. However, the real problem arises when a tree is stressed (usually brought about by spring drought). Here, rather than branch tips, bark beetles attack the trunk of the tree. Here, beetles bore under the bark and lay eggs in a vertical line 1 to 3 inches in length. When the eggs hatch, the larvae eat the inner bark radiating outward from the central egg-laying gallery creating a "centipede-like" gallery pattern. The larval feeding activity girdles the tree, interrupting the flow of nutrients, and usually kills it. The infestation occurs during spring and summer and there is usually one generation per year. Pruning and disposal of infested twigs and branches can help reduce populations, but maintaining a healthy tree will reduce the chances of infestation. Slow, deep, infrequent watering of cypress trees is critical to preventing significant losses. In years like this, irrigation should have been started in January/February. In wetter years, irrigation is critical during May and June until monsoon rains begin. A properly designed drip irrigation system or soaker hose placed at the drip line of the tree will do the job. There is no practical control for cypress bark beetles once they have attacked the trunk of a tree. Some merchants are suggesting that injection type insecticides (such as Acecaps) will kill bark beetles. There is no research-based information to support this claim and even the manufacturers do not label these products for bark beetle control. During severe outbreak years, cypress bark beetles have been known to attack seemingly healthy, well-cared-for trees. Populations can also build up in piled slash and unseasoned firewood. It is critical that this material be removed from sites where there is risk to nearby landscape trees. Firewood can be tarped with clear plastic in a sunny location as long as utmost care is taken to completely seal off the plastic to prevent escape of adult beetles. Using this method, the clear plastic will allow light to enter and the heat will kill any beetles that remain in the wood. Forest health issues are becoming increasingly important to Cooperative Extension. Historically, the Arizona State Land Department (ASLD) responded to calls regarding forest insects and diseases on private and state lands. Recently, these responsibilities were transferred to the University of Arizona Cooperative Extension. Previously, Bob Celaya, ASLD Forest Health Specialist, handled forest pests and diseases. Bob knows his forest pests and did a great job helping people with these issues over the years. For now, you can call me (928-445-6590) to assist you with forest pest and disease problems in Yavapai County. The University of Arizona is in the process of hiring a new U of A Forest Health Specialist that will have statewide responsibilities. 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 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/. |