Some Biological Investigations of the Smaller European Elm Bark Beetle in Missouri with Reference to Systemic Insecticidal Control12

Abstract

The recent use of short-lived systemic insecticides for control of the twig-feeding activities of Scolytus multistriatus (Marsham) has emphasized the need for more knowledge of the biology of this species at southern latitudes. Field-rearing studies were conducted in 1965, 1966, and 1967 in Boone County, Missouri, to provide such information. The life history of S. multistriatus was found to include 2 complete and a partial 3rd generation each year. The 1st generation initial emergence varied from mid-April to early May. Peak 1st-generation emergence dates occurred 2-3 weeks after initial emergence. Secondgeneration emergence began the 1st or 2nd week of July, with a peak occurring the 3rd or 4th week of July. Thirdgeneration emergence began the last week of September and continued to November. Peak 3rd-generation emergence dates are indefinite. The 1st-generation emergence constituted about 86% of the total seasonal emergence. Spathius Greatest Ashmead was the most common insect parasite. Greatest parasitization by S. canadensis appeared to occur in partial shade locations of brood material of the 2nd generation of beetles. Enoclerus nigripes var. dubius Spinard was the most common insect predator. Greatest predation appeared to occur with the 2nd generation of bark beetles.