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Epiphytotics of the Columbian timber beetle, Corthylus columbianus Hopkins, and the conditions leading to them can be defined through examination of egg cradle densities for individual trees, attack densities for individual trees average attack densities for all hosts. and the percentage of hosts attacked. The most valid expression of Columbian timber beetle populations through time is the number of cradles (egg chambers) per square foot of bark surface at the ring where the attacks were initiated. On this basis an outbreak is defined as densities greater than long-term averages. A general equilibrium position of 3.36 was established for the beetle; epiphytotics occurred in 1948-51,. 1956. and 1959-61. Outbreak conditions always existed when the number of attacks per square foot on the lower 3 feet of the hole exceeded 0.7 or when 59% or more of the trees were attacked. Conditions prior to outbreaks were defined as 26% or more of the trees attacked for 2 successive years, and 0.3 or more attacks per square foot for 3 successive years preceding the outbreak. Future surveys may employ frequency-density relationships to predict magnitude of field populations.
Document Type: Research Article
Publication date: February 1, 1967
More about this publication?
Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.