Susceptibility of Seed Maggot Flies, Hylemya spp., to Contact Applications of Aldrin, DDT, and Diazinon1

Abstract

In southwestern Ontario, two closely related species of seed maggots are present, the seed-corn maggot, Hylemya cilicrura (Rondani), and the bean seed fly, Hylemya liturata (Meigen). Because of their marked similarity, the two species are often referred to as the cilicrura-liturata complex. Prior to the development of aldrin resistance the ratio of cilicrura:liturata was 9: 1; subsequently, liturata became the predominant species. Tests with DDT and diazinon on adults of two strains of liturata collected in the tobacco belt and in the field crop belt of southwestern Ontario and on a susceptible laboratory strain of cilicrura indicated that the insecticides were equitoxic to both species. However, the strain from the tobacco belt was 255 times as resistant to aldlrin, and the strain from the field crop belt was 7 times as resistant to aldrin as the susceptible laboratory strain. Seed maggot resistance to the cyclodiene-type insecticides became a problem of economic importance in the tobacco belt in 1958 after 4 consecutive years of broadcast applications of aldrin and heptachlor. After 4 years of seed treatment utilizing aldrin, dieldrin, or heptachlor, seed maggot resistance is slowly developing in the field crop belt. Approximately 50% of the population in the field crop belt was resistant to aldrin, but the problem is not yet of economic importance. It is possible that adverse weather conditions, and a high incidence of disease in the spring of 1962 may have successfully controlled the resistant individuals in the population.