Integrated Pest Management: A Seattle Street Tree Case Study
Public concern about pesticide safety and environmental contamination requires that urban foresters move from reacting to apparent pest problems to a proactive mode of examining all aspects of a problem. A study of oystershell scale (Lepidosaphes ulmi Linne) which was “causing the decline of ash (Fraxinus sp.) cultivars along Seattle’s streets” serves as a case study. Had we reacted to the oystershell scale without examining the site, trees, and scales, we would have developed a control program that would have missed the “target” altogether. The majority (59.7%) of the declining trees examined had only light or no scale infestation. Also, there were many trees with heavy scale infestations which looked quite healthy. In Seattle, the scale hatched 2 to 8 weeks later than any of the dates reported in the literature. In checking the original research reports, conflicting results of the effectiveness of dormant “sprays” were found. And finally, there was good evidence that this insect would be a good candidate for parasite or predator augmentation.