Efficacy of jackfruit protease inhibitor and Bt protein against yellow and pink stem borers of rice

An investigation was conducted during 2009–10 and 2010–11 to evaluate the biological activities of jackfruit protease inhibitor and Bt toxins against Scirpophaga incertulas (yellow stem borer) and Sesamia inferens (pink stem borer). Lethal dose (LD50) was estimated against the II^nd instar larvae in laboratory condition. The LD50 of jackfruit cysteine protease inhibitor (CPI) was 25.6±0.14 μg g⁻¹ and 22.5±0.42 μg g⁻¹ against the yellow stem borer (YSB) and pink stem borer (PSB), respectively. However, the LD50 of Bt toxin was 4±0.32 μg g⁻¹ in case of YSB and 2.5±0.38 μg g⁻¹ for PSB. The inhibitory activity of jackfruit protease inhibitor against YSB and PSB can be considered for the management of YSB and PSB either as single protease inhibitor or fused with Bt toxin in rice.