Toxicological Studies on Cutworms. IX. Laboratory and Microplot Field Studies on Effectiveness and Persistence of some Experimental Insecticides Used for Control of the Darksided Cutworm12
Laboratory and field microplot studies were conducted to assess the effectiveness of 20 insecticides against Euxoamessoria (Harris) attacking flue-cured tobacco, Primary screening tests in the laboratory indicated that 6 of 19 insecticides were equally or more effective by direct contact titan DDT, hut all were less effective than chlorpyrifos. Secondary screening tests conducted in the laboratory on 3 of these insecticides, Bay 77049 ( O, O -diethyl O -(2-chinoxalyl) phosphorothioate), Biothion® ( O, O' -thiodi- p -phenylene) O, O, O', O' -tetramethyl phosphorothioate), and leptophos, indicated that all were effective as soil and or stomach poisons. Microplot field trials showed that leptophos and Bay 77049 were more effective than chlorpyrifos as rye cover-crop treatments. Biothion was less effective than chlorpyrifos but more effective than Stauffer N-2596 ( S-(p -chlorophenyl) O -ethyl ethylphosphonodithioate). Residue studies indicated that N-2596 and chlorpyrifos dissipated quickly from the rye cover crop. Leptophos and Biothion were more persistent. In soil Biothion was most persistent > leptophos > N-2596 > chlorpyrifos. No detectable residues of any of the insecticides were found on the fresh tobacco leaves at harvest.