Seasonal Development of the Smaller European Elm Bark Beetle in Southern California

Abstract

Since its initial California find in San Jose in March 1951, the smaller European elm bark beetle, Scolytus multistriatus (Marsham), has spread rapidly to most of the elm-growing areas of this State. Owing to the many drought-weakened elm trees, it has become a particularly serious pest in southern California on both native and imported elms. To be able to suggest to spray-operators appropriate times to spray for the beetles, it was essential to learn something of its development under southern California conditions. It was reasoned that the number of generations of beetles might be more here, and consequently spraying dates might vary considerably, as our winters are mild and the growing season longer, compared with the Northeastern United States, where this well-known insect has been studied thoroughly.