Control of the Apple Sucker, Psylla mali Schmidb., by the Fungus Entomophthora sphaerosperma (Fresenius)

Abstract

The apple sucker, Psylla mali Schmidb., was first noticed in large numbers in Nova Scotia in 1919 and within a few years populations were dense in apple orchards throughout the Annapolis Valley (Dustan, 1924a). Dustan (1924b) and Gilliatt (1924) reported that a disease caused by Entomophthora sphaerosperma (Fresenius) was prevalent among adult apple suckers during this infestation. A decline in numbers followed this early infestation due, it was thought, to the fungus. However, about the time that this early infestation declined sulphur was introduced as a fungicide. General use of sulphur continued until about 1950 and the insect was not a serious pest during this period. This association of low density of the apple sucker with the use of sulphur and the general increase in numbers of the apple sucker after the organic fungicides, ferbam, captan, glyodin, etc. became common in Nova Scotia, led to the belief that sulphur rather than E. sphaerosperma had been largely responsible for the decline of the early infestation in the 1920's.