Laboratory Tests of Insecticides Against Eggs and Larvae of the Cabbage Looper1

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Abstract
Laboratory tests were conducted on laboratory-reared cabbage loopers ( Trichoplusia ni (Hbn.)) to determine the toxicity of six insecticides applied at three rates to eggs and various larval instars. Phosdrin® (1-methoxycarbonyl-1-propen-2-yl dimethyl phosphate) was the most effective ovicide. All doses of Sevin® (1-naphthyl methylcarbumate) and 2 pounds of DDT per acre were moderately effective on eggs. First instar larvae were relatively susceptible to all of the insecticides but endrin and Thiodan® (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin-3-oxide) produced extremely high mortality, while Phosdrin and Sevin were the least effective. Larvae in the second and the third instars were progressively less susceptible to the insecticides tested. Endrin and Thiodan were the most effective materials used for control of larvae through the third instars. None of the insecticides was effective against larvae in the fourth and fifth instars. For effective control of the cabbage looper it will he necessary to apply insecticides before the larvae attain the fourth instars.