Some Effects of Certain “Inert” and Toxic Substances Upon the Twelve-Spotted Cucumber Beetle, Diabrotica Duodecimpunctata (Fab.)

Abstract

Adult twelve-spotted cucumber beetles, Diabrotica Duodecimpunctata (Fab.) were heavily dusted with a number of pulverized substances. The effectiveness of the materials, based upon the time to kill 50 per cent of the beetles, followed in the order: Sodium fluosilicate = calcium arsenate > acid lead arsenate > commercial calcium hydroxide = kaolin > gypsum > bentonite. Beyond the points of 50 per cent mortality, the survival curves of calcium hydroxide and of kaolin diverge widely, indicating a greater effectiveness, under these conditions, for the former substance. Examinations of the digestive tracts of dusted beetles before or after death showed that in most instances the ingested bentonite, gypsum, kaolin or calcium hydroxide had passed into the posterior half of the digestive tract. The presence of the more active arsenicals and sodium fluosilicate was not detected in the gross examinations of the digestive tract.