Balsam Woolly Adelgid in Western North America: Can We Manage It?
Invasive species represent a serious threat to the health of natural systems throughout North America. Balsam woolly adelgid, Adelges piceae (Ratzeburg) (Hemiptera: Adelgidae) (BWA), was introduced to the United States around 1900 and is considered a severe pest of native true firs. In western North America, the balsam woolly adelgid was discovered in California in the 1930s on grand fir (A. grandis), noble fir (A. procera) and European silver fir (A. alba). During the 1950s and 1960s infestations were observed in Oregon, Washington and British Columbia on grand fir, pacific silver fir (A. amabalis) and subalpine fir (A. lasiocarpa). Today the insect continues to disperse eastward across Idaho into Wyoming, northward into western Montana and British Columbia and southward into Utah. BWA causes degradation in tree quality due to swelling of nodes, branch dieback, and cessation in terminal growth, and frequently kills trees. In managed settings such as Christmas tree farms, insecticides continue to be the only successful way of dealing with BWA. In wildland forests, biological control has been employed with mixed success. The literature indicates there are not many effective measures of prevention through forest management practices. In 1957 after three years of study, 26 species of arthropods were found associated with the balsam woolly aphid in the Pacific Northwest. In the 9 years from 1957 through 1965, 23 species of insect predators from 7 countries were introduced. Five species became established; a 6th produced progeny, then disappeared. Presented by Robert Progar, USDA Forest Service, at the 2018 SAF National Convention, Portland, OR