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Evaluation of Douglas-fir mortality from Douglas-fir beetle from 1982 through 1984 following MCH application Public Deposited
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A granular controlled release formulation of 2 percent MCH was applied at 4.48 kg/ha to 76.9 ha of uninfested, windthrown Douglas-fir by helicopter with a modified aerial spreader of 1.12 m capacity in May 1982. Douglas-fir beetle population reduction was 96.4 percent by late June. With one exception, treated plots had no successful attacks through 1984. Successfully attacked trees in stands surrounding treated plots declined sharply by the second season. This may indicate MCH dispersed beetles over a wide area preventing the development of many epicenters. Mortality remained high in check areas and surrounding stands. In all areas surrounding treated blocks and check areas, the number of pitchouts increased and average diameter of successfully attacked trees declined with successive years of infestation. This pattern is indicative to that experienced following a beetle population buildup in windthrow in other areas. We recommend MCH be registered at 2 percent controlled release formulation for application to inaccessible windthrown trees, and to protect adjacent high-value stands.
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