Title: Evaluation of Biological Activity of Bacillus thuringiensis Test Samples Using a Diet Incorporation Method with Diamondback Moth, Plutella xylostella(LINNAEUS)(Lepidoptera:Yponomeutidae)
Abstract: Bioactivity of 2 test samples (KM301 and KM202) in wettable powder form which contain δ-endotoxin of Bacillus thuringiensis was evaluated by a diet incorporation method with a laboratory colony of the diamondback moth larvae, Plutella xylostella. Time-mortality curves and time-LC50 curves for the 2 samples were differed from each other. KM301 showed relatively rapid lethal activity in 2-3 days and KM202 had slower lethal activity in 3-14 days. However, time-pupation curves and time-EC50, the relative potency of KM202 differed from KM301 depending on the day on which the mortality rates were determined. Compared with KM301, the bioactivity of the KM202 was lower at 2-3 days, similar to it at 4 days, and higher at 5-14 days. However, an evaluation based on EC50 showed that the KM202 was always superior to the KM301, regardless of reading days. The bioactivity of 2 samples evaluated by both diet incorporation and the leaf dip methods showed little difference between them, indicating that the relative potency was not changed by the bioassay methods.