A SAMPLING DESIGN FOR THE EGG AND FIRST INSTAR LARVAL POPULATIONS OF THE WESTERN PINE BEETLE, DENDROCTONUS BREVICOMIS (COLEOPTERA: SCOLYTIDAE)

Abstract

The distributions of attack, gallery length, eggs, and first instar larvae of an endemic population of the western pine beetle in ponderosa pine are described. Mean gallery length (GL) and larval (L) densities of mature populations are significantly correlated with attack (A) density. The associations are adequately described by the simple linear regressions The ratios E/GL and L/GL are stable over a wide range of gallery length densities and consequently egg-gallery length and larval-gallery length correlations are highly significant. The regression equations are All four equations predict values within 10% of observed values.An 88 cm2 sampling unit is satisfactory for sampling either egg or first instar larval populations. Taking four paired sampling units, evenly spaced along the infested bole, from each of four trees per generation, provided a sampling precision of 15%. Increasing the number of paired units to 10 and the number of trees sampled per generation to 9 improved the precision to 10%. If the trees are sampled before oviposition is complete, the number of sampled trees per generation should be increased by 1 for each level of precision.