Toxicity and efficacy of triazamate against turnip aphid (Homoptera : Aphididae) on cabbage

Toxicity of triazamate (Aphistar((R)), Rohm & Haas, Philadelphia, PA) to a laboratory and afield population of the turnip aphid, Lipaphis erysimi (Kal tenbach), was studied on cabbage in the laboratory, and the efficacy of tri azamate against the aphid was tested in the field in comparison to lambda-c yhalothrin (Warrior((R)), Zeneca, Wilmington, DE) and imidacloprid (Provado ((R)), Bayer, Kansas City, MO) in 1999 and 2000, Results from the laborator y bioassays indicated that field populations of L. erysimi apterous adults and nymphs were significantly less susceptible to triazamate than the labor atory population. The LC50 values for adults, early and late instars of the field population were 6.7-, 2.7-, and 1.4-fold greater than the correspond ing stages of the laboratory population, respectively. Similarly, the LC90 values for adults, early and late instars of the field population were 6.4- , 2.6-, and 1.7-fold greater than the corresponding stages of the laborator y population, respectively. Results from field trials in 1999 and 2000 show ed that triazamate and lambda-cyhalothrin reduced the aphid population fast er than imidacloprid after the first application. Triazamate was as effecti ve as lambda-cyhalothrin with low aphid population levels on the plants thr oughout the season except the last 2 wks in the 1999 trial. In the 2000 tri al, an extremely high aphid population was found on untreated plants, where as two applications of triazamate, as well as lambda-cyhalothrin and imidac loprid, kept aphid population levels suppressed for the entire season.