Toxicity and Efficacy of Triazamate Against Turnip Aphid (Homoptera: Aphididae) on Cabbage

Abstract

Toxicity of triazamate (Aphistar®, Rohm & Haas, Philadelphia, PA) to a laboratory and a field population of the turnip aphid, Lipaphis erysimi (Kaltenbach), was studied on cabbage in the laboratory, and the efficacy of triazamate against the aphid was tested in the field in comparison to lambda-cyhalothrin (Warrior®, Zeneca, Wilmington, DE) and imidacloprid (Provado®, Bayer, Kansas City, MO) in 1999 and 2000. Results from the laboratory bioassays indicated that field populations of L. erysimi apterous adults and nymphs were significantly less susceptible to triazamate than the laboratory 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 corresponding 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 laboratory population, respectively. Results from field trials in 1999 and 2000 showed that triazamate and lambda-cyhalothrin reduced the aphid population faster than imidacloprid after the first application. Triazamate was as effective as lambda-cyhalothrin with low aphid population levels on the plants throughout the season except the last 2 wks in the 1999 trial. In the 2000 trial, an extremely high aphid population was found on untreated plants, whereas two applications of triazamate, as well as lambda-cyhalothrin and imidacloprid, kept aphid population levels suppressed for the entire season.