The Varietal Reactions of Cucumbers to DDT and Methoxychlor Dusts

Abstract

Although DDT gives excellent control of the striped cucumber beetle, Acalymma vittata (F.), the most serious insect pest of cucumbers in Canada, the technical grade of DDT is generally considered too toxic to cucumbers to he used on that crop with safety. Recently, two related materials that are said to be less toxic to cucurbits in general have been on the market: high-setting-point DDT, and methoxychlor. Carruth and Howe (1948) showed that DDT approaching aerosol grade in setting-point was less injurious to squashes than DDT of technical grade. Several entomologists have reported that cucumbers, like melons and squashes, show definite varietal responses to DDT. Hervey and Schroeder (1946) found the variety Ohio 31 to be more severely injured by DDT than China or Chicago Pickling. Wilson and Sleesman (1947) reported that plants of Ohio 31 were stunted much more by DDT than those of National. This paper is a report on three seasons' investigations of the toxicity of three per cent technical-grade DDT dust to 12 varieties of cucumbers, and one season's investigations of the toxicity of three per cent high-setting-point DDT and methoxychlor dusts to the same 12 varieties.