Abstract
AbstractDamage at cone harvest by the Douglas-fir cone gall midge, Contarinia oregonensis Foote, was positively correlated with the number of egg-infested scales per conelet in the spring. Reducing the average number of galled seeds per cone by 1.5 increased the average number of filled seeds per cone by 1.0 in insecticide trials. Optimum sample sizes for estimating average densities of egg-infested scales were calculated to be one conelet per tree and 150 trees per orchard. The mean crowding variable was linearly related to average density so a sequential sampling technique relative to a critical density, using Iwao’s procedure, was developed for determining the need of control actions.
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