EVALUATION OF BIOLOGICAL-ACTIVITY OF BACILLUS-THURINGIENSIS TEST SAMPLES USING A DIET INCORPORATION METHOD WITH DIAMONDBACK MOTH, PLUTELLA-XYLOSTELLA (LINNAEUS) (LEPIDOPTERA, YPONOMEUTIDAE)

Bioactivity of 2 test samples (KM301 and KM202) in wettable powder for m which contain delta-endotoxin of Bacillus thuringiensis was evaluate d by a diet incorporation method with a laboratory colony of the diamo ndback moth larvae, Plutella xylostella. Time-mortality curves and tim e-LC50 curves for the 2 samples were differed from each other. KM301 s howed relatively rapid lethal activity in 2-3 days and KM202 had slowe r lethal activity in 3-14 days. However, time-pupation curves and time -EC50 (based on pupation inhibition) curves were not different from ea ch other except in applied dose levels. When the bioactivity of the 2 samples was compared based on LC50, the relative potency of KM202 diff ered from KM301 depending on the day on which the mortality rates were determined. Compared with KM301, the bioactivity of the KM202 was low er at 2-3 days, similar to it at 4 days, and higher at 5-14 days. Howe ver, an evaluation based on EC50 showed that the KM202 was always supe rior to the KM301, regardless of reading days. The bioactivity of 2 sa mples evaluated by both diet incorporation and the leaf dip methods sh owed little difference between them, indicating that the relative pote ncy was not changed by the bioassay methods.