Intensity of Attacks by Scolytus multistriatus at Distances from Dispersion and Convergence Points1

Abstract

Twig-crotch injuries by the smaller European elm bark beetle, S. multi-striatus, a vector of the Dutch elm disease fungus, were found more frequently around a dispersion point than around points where the beetles came for breeding. The average rates of crotch-injury decrease with distance increases from the dispersion point for 1940 and 1941 were similar. The incidence of twig-crotch injury around the dispersion-convergence point was similar to that around the dispersion point and dissimilar to the much lower rates around the convergence points. Brood galleries may be found as far as 4 miles from the place where the beetles that constructed them emerged.