TWIG FEEDING BY SCOLYTUS MULTISTRIATUS (COLEOPTERA: SCOLYTIDAE): WITHIN-TREE DISTRIBUTION AND USE FOR ASSESSMENT OF MASS TRAPPING

Abstract

AbstractTwig-feeding injuries by S. multistriatus in juvenile white (or American) elms occurred primarily (61%) in the upper 1/3 of the crowns. Preferred feeding sites were crotches formed by the previous year's and current year's twig growth (both spring and summer) and by leaf petioles from current year's twig growth (summer only). An index of twig feeding appeared to reflect S. multistriatus population trends and was closely correlated with Dutch elm disease rates in Syracuse, N.Y., from 1978 to 1982. Twig-feeding indices and catches on sticky traps baited with S. multistriatus pheromone were generally correlated, but disparate when competing natural pheromone sources were abundant. Twig sampling indicated that S. multistriatus populations and disease rates were reduced by mass-trapping and trap-tree techniques. The twig-sampling method presented appears to be useful in predicting Dutch elm disease rates and assessing the effectiveness of measures to control its beetle vector.