Emergence of Pissodes strobi (Coleoptera: Curculionidae) from Previously Attacked Sitka Spruce1

Abstract

Preliminary studies in southwestern Washington indicated that more Sitka spruce weevils, Pissodes strobi (Peck), emerged from previously unweeviled Sitka spruces, Picea sitchensis (Bong.) Carr, than from previously attacked trees. Weevil emergence was sampled at a plot 7 miles south of Humptulips composed of one hundred and fifty 12-year-old trees; half of the trees had been attacked that spring (1971). Stem cages (Gara et al. 1971) were placed over leaders of trees which contained egg punctures. Later in the fall, emerging adults were collected from the cages and counted daily. The study revealed that 70% of the weevils, emerging between August and September, originated from trees attacked for the 1st time. The mean number of weevils emerging per tree also was considerably higher from terminals showing no indication of previous infestation than from stems weeviled 2—3 years previously.