Further Field Experiments on the Use of Bacillus thuringiensis and Chemical Insecticides for the Control of the European Corn Borer, Ostrinia nubilalis, on Sweet Corn in Southwestern Quebec

Abstract

In 1961, two preparations of Bacillus thuringiensis Berliner, one, Thuricide® (30✕109 spores per g.) and the other Bakthane® L-69 (75✕109 spores per g.), both used at 2 Ib of wettable powder per acre were compared with: DDT, 1½ lb; Sevin® (1-naphthyl N -methylcarbamate), l lb; Sevin 4 flowable, l lb; Kepone® (decachlorooctahydro-1,3,4-metheno-2 H -cyclobuta [cd] pentalen-2-one), 1 lb; Dylox® ( O,O -dimethyl 2,2,2-trichloro-1-hydroxyethyl phosphonate), 1½ lb; EPN ( O -ethyl O-p -nitrophenyl phenylphosphonothioate), 1 lb; Zectran® (4-dimethylamino-3,5,-xylyl methylcarbamate), 1 lb; Bakthane L-69 2 lb plus half dosage of DDT. In 1962, two preparations of B. thuringiensis at 2 lb per acre, 2 lb plus half dosage of DDT, were compared with DDT at 1 and 1.5 lb, Sevin, Dylox, Kepone, EPN, Zectran at the 1961 dosages, Bayer 44646 (4-dimethylamino- m -tolyl methylcarbamate), l lb and Thiodan® II (hexachlorohexahydro-6,9-methano benzodioxathiepin-3-oxide), 1 lb per acre for the control of the European corn borer, Ostrinia nubilalis (Hubner), on sweet corn in southwestern Quebec. Each year, in mid-July, two applications were made at a week interval with a conventional tractor-pulled sprayer. Percent infested plants and ears and numbers of borers in the plants were obtained by dissecting at harvest 25 corn plants per replicate per treatment. In general, results were similar for the two years and none of the materials tested were phytotoxic at the doses used in these experiments. In 1961, all treatments gave more than 94% marketable ears. DDT, EPN, Sevin and Dylox reduced the number of larvae in the plants by 72% or more; the Bakthane L-69-DDT mixture and Thurieide, 69%; Sevin flowable, Zectran, Kepone and Bakthane L-69, from 54.7% to 64.3%. In 1962, all treatments gave more than 96% marketable ears. EPN reduced the number of larvae in the plants by 97.9%; Thuricide, DDT, Dylox, Bak-thane L-69, Bayer 44646, from 80.9% to 89.3%; Kepone, Zectran, the Bakthane L-69-DDT mixture, from 72.4% to 78.6%; Sevin, 68.1%. Thiodan II, 53.3%. In 1961, 77.9% of the ears in the untreated plots were marketable; in 1962, 86.7%. The percentage of untreated plants damaged in 1961 was 52; in 1962, 25.3. B. thuringiensis at 2 lb per acre under low or moderate corn borer infestations gave good control. The results of this 2-year study indicate that B. thuringiensis is reasonably effective in controlling corn borer, but not so significantly superior to several chemical insecticides to be considered as more than a promising microbial control measure against this insect.