Artistic Arborist, Inc. - Complete Tree Health Management
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Artistic Arborist, Inc. - Complete Tree Health Management |
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(602) 263-8889 |
Tree Alert! Carpenterworms Discovered In Phoenix Andrew Backhaus, Ph.D.
A new warning to Phoenix area homeowners with large trees is to be on the lookout for carpenterworms. These are among the most aggressive wood boring insects known in North America. Until now, Arizona has been relatively free of this pest but a small outbreak discovered in June 2004 in a neighborhood surrounding 34th St and Osborn should put us on guard to track the spread of these potentially devastating insects. The injury from carpenterworms occurs quickly; only a few larvae are needed to kill a full-grown tree in a single season. Unlike most wood boring insects, the feeding damage from carpenterworms is unique, resulting in deep fissures that run across the bark and easily girdle large trunks. Advanced wounds resemble damage caused by a chain saw (see Figures above) or the wounds caused by embedded tree stake wires. During our first encounter we actually asked our client if he had any angry neighbors. It wasn’t until we observed the same damage in limbs 20 ft. up that we realized there was no way even the angriest neighbor would have been able to carry a chainsaw to that height!
Carpenterworms are the larval stage of the moth, Prionoxystus robiniae, that attacks many deciduous tree species throughout North America. Fortunately, these insects produce no more than one generation per year and have a life cycle that lasts 2-4 years. The brown-gray adult moths (shown above) have a wing span of 2-3 inches and emerge from pupae (above center) in April through June. The adult moths are large and heavy and can only fly a few yards, surviving one week before mating. Carpenterworms favor deciduous trees such as elms, ash, cottonwoods and fruit trees. The females lay masses of small eggs in bark crevices that hatch after about two weeks. Hatching larvae bore through egg cases and into the wood where they survive for 2-4 years, depending on climate. During this time they burrow into the heartwood and cambium growing to 2 inches long. As the larvae enlarge, their tunnels increase in size forming pencil-diameter holes that cause severe tree damage. The wounds produce bark fissures that exude large quantities of sap and sawdust. Carpenterworms are attracted to native species that grow in moist, riparian soils. In urban settings, infestations occur in flood-irrigated landscapes and orchards. Because carpenterworms can not fly great distances they do not spread rapidly. Initial carpenterworm damage tends to go unnoticed because the borer holes are small. However, as larvae grow and wound size increases, the damage becomes more noticeable. By this time it may be too late to save the tree. Infested wood should be pruned judiciously to delay insect spread. In some cases a stiff wire can be plunged into borer holes to puncture the larvae. However, this is only effective with mild infestations. Controlling carpenterworms with conventional insecticide sprays is difficult. Soil applied, systemic insecticides are NOT effective. If detected early, trunk microinjections of bidrin between April and August can control the insect, however, this treatment requires a licensed applicator. A much safer and potentially more effective treatment is possible with commercial sprays of Beauvaria bassiana, a fungus that produces chitinase that dissolves the worms exoskeleton within 72 hours. The sprays can be directed at the trunk and branches (not leaves) and concentrated on the crevasses and borer holes where the larvae are likely to come in contact with the fungus. The beauty of this fungus is that it is a living organism that can regenerate itself and provide potential long-term control. Also, commercial formulations of an entomophagus nematode Steinernema feltiae (Neoaplectana carpocapsae), available as Scanmask, are known to control carpenterworms. Always follow supplier's directions for application when using such preparations. Carpenterworms are typically found in colder climates such as Nebraska, Colorado, and Utah and the infestation discovered in Phoenix during this past summer (2004) is quite unusual. The area where we first encountered them is confined to a 2-mile radius around 34th St. and Osborn Rd. We don't now if infested areas exist beyond this zone but are interested to know if others have encountered them. If you have any additional information about carpenterworms please let us know so we can pass it along to the public. |
