Abstract: Bioassay of JDS-CPV was conducted on the 3rd instar and 5th instar larvae of pine caterpillar D. punctatus. The regression equations between concentration and mortality for 3rd instar and 5th instar were Y=2.44+0.49x and Y=1.83+0.57x, LC₍₅₀₎ value were 1.6×10⁵PIB/mL and 3.3×10⁵PIB/ml respectively. The regression equation between the count of PIB and mortality for 3rd instar larvae is Y=1.72×0.98x, LD₍₅₀₎ value is 2.1×10³PIB/larvae. For example as 1×10⁸PIB/ml, the LT₍₅₀₎ value for 3rd instar and 5th instar larvae were 8.5 days and 13 days respectively. The results showed that the JDS-CPV has higher virulence to pine caterpillar.

Key words: Pine caterpillar, Cytoplasmic Polyhedrasis Virus, Bioassay