Experimental Prevention of Bark Beetle Transmission of Ceratocystis ulmi (Buis.) Moreau with the Systemic Insecticide Chipman R-61991

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Abstract
Trunk-implantation treatment of American elm trees with any of three dosages of the systemic insecticide Chipman R-6199 (O,O-diethyl S-(2-diethylamino)-ethyl phosphorothioate [hydrogen oxalate salt]) was effective in preventing bark beetle transmission of Ceratocystis ulmi (Buis.) Moreau. Successful bark beetle transmission of the fungus in control trees occurred only from beetle cagings during the interval from May '10 through .June 10. During this period, 30% of the control trees became infected with the fungus and showed symptoms of the disease, The mean length of beetle-feeding niches was always 1.5 mm. or less in treated trees, and 3.3 mm. or greater in control trees. In every diseased tree, the minimum-length niche that penetrated at least to the cambium was 3 mm. long. On the basis of this limited knowledge of niche-length requirements, a 96.3% reduction in the number of infectible niches resulted from insecticidal treatment. The insecticide, at '10grams per tree, was effective in reducing the length of feeding niches for the entire 80-day study perriod following treatment.

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