Phenological Events Associated with the Spring Emergence of the Smaller European Elm Bark Beetle in Dubuque, Iowa

Abstract

Spring emergence of the smaller European elm bark beetle, Scolytus multistriatus (Marsham), was studied in 1964, 1965, and 1966 in Dubuque, Iowa, in relation to other spring phenomena influenced by weather. The time of blooming of common trees and shrubs was observed and beetle emergence was determined by observing both standing elm trees within the city and caged infested elm material. From this, a flowering sequence of 4 plants which bloom prior to S. multistriatus emergence was established. In 1964 and 1966 S. multistriatus emergence began between the time of initial full bloom of the purple lilac, Syringa vulgaris L., and bridal wreath, Spiraea Vanhouttei (Briot) Zab., and in 1965 it coincided with the first day of full bloom of bridal wreath. Emergence of S. multistriatus began 10 days later in 1966 than in 1964, but the sequence of events remained unchanged.