Control of the weevil (Amnemus quadrituberculatus) in tropical legume pastures with dieldrin and heptachlor pre-sowing soil treatments

Abstract

Three experiments on chocolate alluvium, chocolate basaltic, and prairie meadow soils, respectively, tested the long term effectiveness of dieldrin and heptachlor pre-sowing treatments in controlling Amnemus quadrituberculatus (amnemus weevil) in tropical legume pastures. The legume species used were Desmodium uncinatum, D. intortum, Glycine wightii and Macroptilium atropurpureum. Both chemicals at rates from 0.56-2.24 kg ha-1 gave high levels of control of the weevil for two years after pasture establishment. Control declined in the third and subsequent years, but in all experiments insecticide treated plots retained the legume components longer than did untreated plots. Heptachlor at 1.12 kg ha-1 proved the best treatment but a general decline in legume density was observed in all experiments.