Biopotency and toxicity of diverse group of insecticides under laboratory condition against sunflower defoliator Spilarctia obliqua (Walker)

The biopotency and toxicity of two groups, conventional and newer insecticides [eight commercial insecticides] were determined against Bihar or Common hairy caterpillar (BHC) Spilarctia obliqua (Walker). Experiment carried out in the laboratory by exposing BHC larvae to insecticides. Biopotency was measured at different time intervals from 12-72 h after insecticidal application showed that all of the insecticides outperformed the control. At 48 h after imposing, the highest mortality percentage (100) was observed on spinetoram 11.7 SC and chlorfenapyr 10 SC, which are comparable to cyantranaliprole 10.26 OD, followed by chlorantraniliprole 18.5 SC, ?-cyhalothrin 5 EC and chlorpyriphos 20 EC, with the lowest mortality percentage observed on tolfenpyrad 15 EC (66.67 %). In chlorantraniliprole, cyantranaliprole, spinetoram, tolfenpyrad, fipronil, chlorfenapyr, ?-cyhalothrin and chlorpyriphos, respectively, the toxicity level of insecticides was calculated based on median lethal concentration (LC50) values of 0.36, 0.48, 0.52, 0.50, 0.69, 0.98, 1.43 and 3.82 ppm. The overall conclusion of this trial was that spinetoram 11.7 SC and chlorfenapyr10 SC are the best chemicals for controlling the early stages of BHC larvae. In comparison to traditional insecticides, new insecticides have the highest level of toxicity

Assessment of Bt trait purity in different generations of transgenic cottons.

Adequate expression of Bt (Bacillus thuringiensis) toxins and purity of seeds of Bt-transgenic cottons are important for controlling bollworms, and thereby increasing the cotton productivity. Therefore, we examined the variability in expression of Bt toxin proteins in the seeds and in leaves of different cotton (Gossypium hirsutum (L.) hybrids (JKCH 226, JKCH 1947, JKCH Durga, JKCH Ishwar, JKCH Varun KDCHH 441 and KDCHH 621) expressing Bt toxins in F1 and F2 generations, using bioassays against the cotton bollworm, Helicoverpa armigera (Hübner), and the lateral flow strip (LFS) test. Toxicity of Bt toxin proteins in the seeds of Bt-transgenic cottons to H. armigera correlated with their toxicity in the leaves in one-toxin Bt cotton hybrids. The Bt-F1 and Bt-F2 seeds of JKCH 1947 were more toxic to H. armigera than those of JKCH Varun seeds. The seeds and leaves of F1s showed greater toxicity than the F2 seeds or leaves of one-toxin (cry1Ac) Bt cotton hybrids. However, no significant differences were observed for the two-toxin (cry1Ac and cry2Ab) hybrid, KDCHH 621. Toxicity of leaves to H. armigera increased with crop age, until 112 days after seedling emergence. The Bt trait purity in F1 seeds of four two-toxin Bt cotton hybrids ranged from 86.7 to 100%. The present study emphasizes the necessity of 95% Bt trait purity in seeds of transgenic cotton for sustainable crop production.

Evaluation of selected insecticides as seed protectants against the maize weevil (Sitophilus zeamais M.).

An investigation was carried out to evaluate the relative toxicity of selected newer insecticides viz., deltamethrin, spinosad, abamectin and emamectin benzoate in comparision with the organophosporus insecticide malathion to the maize weevil, Sitophilus zeamais Motschulsky, in an attempt to find out a safer and effective seed protectant. The LC50 values based on bioassay studies indicated that among the test insecticides, deltamethrin exhibited greater toxicity both at 24 and 48 hours of exposure. The relative toxicity of deltamethrin, abamectin, spinosad, and emamectin benzoate were 1.06, 1.005, 0.07 and 0.01 at 24 hours and 1.18, 1.08, 0.11 and 0.02 at 48 hours of exposure compared to check malathion.