ESTIMATION OF EGG POPULATIONS OF THE ALFALFA WEEVIL, HYPERA POSTICA (COLEOPTERA: CURCULIONIDAE)

Abstract As part of a detailed study of the life system of the alfalfa weevil, Hypera postica (Gyll.), in southern Ontario, two methods were developed for estimating numbers of eggs in the spring growth of alfalfa. The first is based on direct counts of the eggs, which are laid in clusters and hence, aggregated in distribution; for moderate levels of infestation (ca. 8 eggs per bouquet), estimates with acceptable precision may be obtained by taking a single 3-stem bouquet of alfalfa from 80 randomly selected ft2 (.09 m2) quadrats within a field. The second is based on counts of the oviposition punctures which are randomly dispersed and consistent with the Poisson distribution. Although slightly less accurate, this method will provide a valid index of the number of eggs with less labour; acceptable precision may be obtained by taking a single bouquet from just 32 quadrats.