DISTRIBUTION OF CONTARINIA OREGONENSIS FOOTE (DIPTERA: CECIDOMYIIDAE) EGGS IN DOUGLAS-FIR SEED ORCHARDS AND A METHOD OF ESTIMATING EGG DENSITY

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Abstract
Efficient sampling procedures for estimating densities of eggs of Douglas-fir cone gall midge (DFCGM), Contarinia oregonensis Foote, on individual trees as well as for orchards were developed from data collected in Douglas-fir seed orchards in 1978–1981. Egg distribution was contagious and generally fitted the negative binomial distribution on individual trees, but a common k could not be estimated. Tree and crown level affected density of midge eggs within orchards. Average density at the midpoint of the cone-bearing portion of the crown was not significantly different from the tree average. The optimum sampling pattern in an orchard, i.e. one conelet from the midpoint of the cone-bearing portion of each of 120 trees, would require 120 person-hours to process the samples when DFCGM egg densities are high (worst-case situation).