RESIDUES OF METHOMYL IN RAPE PLANT AND SEED FOLLOWING ITS APPLICATION FOR THE CONTROL OF BERTHA ARMYWORM, MAMESTRA CONFIGURATA (LEPIDOPTERA: NOCTUIDAE)

Abstract

Residues of methomyl in rape plants and seed were determined after its application for bertha armyworm control. In one experiment application of 3 oz of methomyl per acre left 17 p.p.m. residue on the rape plants immediately after application. This level rapidly declined to 1.5, 1.0, 0.4, and 0.2 p.p.m. 1, 2, 5, and 9 days later, respectively, and no residue was detected (less than 0.02 p.p.m.) in seed harvested 22 days after application of the toxicant. Rape plant samples collected from several farms immediately after the application of 3 to 4 oz of methomyl per acre had 2.5 to 16 p.p.m. residues, indicating inefficient application of the insecticide in some cases. Analysis of rape seed samples collected from 36 farms showed little residue in three samples (0.02 to 0.03 p.p.m.) and none in 33, indicating that the use of methomyl for bertha armyworm control is not likely to contaminate rape seed with undesirable levels of residues.

EVIDENCE FOR CIS-11-HEXADECEN-1-OL ACETATE AS A MAJOR COMPONENT OF THE SEX PHEROMONE OF THE BERTHA ARMYWORM, MAMESTRA CONFIGURATA (LEPIDOPTERA: NOCTUIDAE)

“…), is an indigenous pest that has inflicted major damage to economic crops of the Canadian prairie provinces. For example, 20% of the 5.5 million acre rapeseed crop was affected by an outbreak in 1971 (Lee et al 1972) with an estimated crop loss of $14 million, notwithstanding $3 million spent on insecticide and application (McDonald 1972). King (1929) reports the insect population density varies considerably from year to year and from area to area within the prairies.…”