Monday, August 19, 2013

Prevent and Manage Wood Boring Insects

To complete my series on wood-boring insects, I'd like to conclude with the management of these bugs. Managing wood-boring insects can be a difficult task and one that is best left to a professional tree service and/or a certified arborist. For the readers that are from the Chicagoland area, you can trust that Trees "R" Us, Inc. will give you honest, accurate and professional advice for all your tree care needs, not just those about wood boring insects.  Now on to the management and prevention of wood borers.

Prevention

Since most wood-boring insects are considered secondary invaders, the first line of defense against infestation is to keep plants healthy. Proper care of trees and shrubs discourages many borer pests and helps infested plants survive. Good sap flow from healthy, vigorously growing trees, for example, defends the plant from damage by many borer pests. Good horticultural practices include: Selecting well adapted species of trees and shrubs that are not commonly attacked by wood borers in your area. Arizona ash, birch, cottonwood, locust, soft maple, flowering stone fruits (such as peaches and plums), slash pines (in west Texas), willow and poplar are especially prone to borer attack. Choosing and preparing a good planting site to avoid plant stress, freeze damage, sun scald and wind burn. Minimizing plant stress and stimulating growth by using proper watering and fertilization practices. Avoiding injury to tree trunks from lawn mowers, weed trimmers or construction.

Promptly caring for wounded or broken plant parts using pruning or wound paint during all but the coldest months of the year. Properly thinning and pruning during colder months. Removing and destroying infested, dying or dead plants or plant parts, including fallen limbs. Wrapping tree trunks and limbs with quarter inch hardware cloth spaced about 1 1/2 inches from the tree’s surface where woodpecker damage is likely. Wrapping trunks to prevent borer attack is ineffective and may, under certain conditions, increase the rate of infestation. Using plastic trunk protectors to help prevent injury from lawn mowers and weed trimmers is a good idea. Non-chemical control for infested plants. Once trees and shrubs are infested, non chemical options for borer control are limited. One option is to remove and destroy heavily infested or injured plants. Also, inspect damage sites closely to determine if the larvae can be extracted from the plant with a pocket knife, wire or other suitable tool.

Chemical control

It is important to remember that stressed, unhealthy trees can be attacked repeatedly and will need repeated applications of insecticide indefinitely. In most cases this is neither economically nor environmentally justified. When chemical treatments are used, efforts always should be made to improve overall tree health. Most of these products are applied as sprays to the trunks and branches, and are non-systemic, residual insecticides (e.g., bendiocarb, carbaryl, chlorpyrifos, endosulfan, esfenvalerate, fluvalinate, lindane, methoxychlor, cyfluthrin, bifenthrin, permethrin, sumithion). While these products do not kill larvae that have already penetrated the sapwood or heartwood, they will kill adults and larvae tunneling through the treated bark layer. This is primarily a preventive treatment. Some products (those containing paradichlorobenzene and ethylene dichloride) act as fumigants to repel egg-laying adults or kill accessible larvae.

Systemic insecticides applied to the soil are ineffective for borer control and few are registered for this purpose. Trunk injection products (containing abamectin, acephate, dicrotophos, imidaclaprid and oxydemeton-methyl) are registered for treatment of some borers. These products are reported to work by delivering insecticides into the cambium and phloem tissues where borers feed. Several factors should be considered when using insecticides to control insect borers:

1. Time your treatments to match adult activity. Knowing when adults lay their eggs is critical, as insecticides are most effective if applied when adults are emerging and eggs are hatching. For the peachtree borer, a single surface application of a contact insecticide in late August or early September can prevent infestations on Prunus species. For most beetles, the adult egg-laying period is either very long or unknown. Surface treatments are effective for only a 3- to 10-week period. Therefore, regular re-treatment of susceptible plant parts is needed for effective control.

2. Be sure coverage is complete and minimize drift. Effective treatment for borers requires that all surfaces of trunks and branches be covered. Only in a few instances (such as for peachtree borer) is treatment of only the base of the tree trunk sufficient to protect the tree. Complete coverage may be difficult on large trees and may result in drift to non-target areas. To minimize drift, spray only on days when wind is less than 6 to 7 miles per hour. When making Sapsucker damage appears as square holes in a tree trunk. 


Treat susceptible plants. Treatment of highly valued landscape trees or vulnerable plants may be justified. Newly transplanted trees and shrubs are naturally stressed and may need treatment, especially when borers are known to attack newly planted trees in the area.

Firewood
Adult wood borers sometimes emerge from firewood stored indoors. While most of these insects are not considered harmful, old house borer and powderpost beetles will attack seasoned, dry wood inside the home. Treating firewood with insecticide is both ineffective  and potentially dangerous to the homeowner. Wood should be stored outdoors away from the house until just before use. If firewood is infested with borers it can be treated by wrapping it in a tarp and allowing sunlight to heat it. Stacking wood layers in alternate directions will help it dry and reduce areas that can harbor insects.


Remember to take care when using pesticides and attempting to treat infestations of insects. When in doubt, call upon a professional.

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