Grain protectants for the control of malathion‐resistant insects in stored sorghum

Abstract

Abstract Duplicate experiments were carried out on bulk sorghum stored in South Queensland and in Central Queensland. Bioassays of treated grain, conducted during 6 months' storage, established that fenitrothion (12 mg kg −1 )+ bioresmethrin (1 mg kg −1 ), and pirimiphos‐methyl (4 mg kg −1 )+ carbaryl (8 mg kg −1 ), controlled typical malathionresistant strains of Sitophilus oryzae (L.), Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), and Ephestia cautella (Walker). Chlorpyrifos‐methyl (10 mg kg −1 )+ pyrethrins (1.5 mg kg −1 )+ piperonyl butoxide (12 mg kg −1 ), and fenitrothion (12 mg kg −1 )+ (1 R )‐phenothrin (1 mg kg −1 ), also controlled the strains of S. oryzae, T. castaneum and E. cautella , but were only partly effective against R. dominica. Methacrifos (15 mg kg −1 ) controlled all the tested species except E. cautella. Chemical assays established that the residues and rates of breakdown of these grain protectants on sorghum conformed to the general pattern for other cereal grains; residues from the above treatments were below the individual Maximum Residue Limits recommended by the Codex Alimentarius Commission.