Assessment of insecticidal top-down effects of new insecticides formulations on numerical tritrophic interaction of Bt-cotton cultivars, sucking insec pests and natural enemies in field and mortality rates of dusky and red cotton bugs in laboratory

Present research involved two experiments including a field experiment to assess insecticidal top-down impact of some new insecticides formulations on tritrophic association of bt-cotton cultivars, sucking insect pest complex and natural enemies and a laboratory bioassay to determine if the field dose rates recommended for other sucking insect pests have contact toxicity for red and dusky cotton bugs. Treatments consisted of six insecticides including Confidor 20% / SL (Imidacloprid), Pouch 35% / SC (Pyriproxyfen + Etafenpron), Senator 41.6% / EC (Imidacloprid + Pyriproxyfen), Blaster 72.5% / WP (Imidacloprid + Acephate), Bugatti 56% / SC (Imidacloprid + Diafenthrion) and Jozer 20.2 % / SL (Imidacloprid + Acetameprid). All the treatments (insecticides) imparted significant variation in the population reduction of all the target insects in field trails. The reduction in population of all the insect pests increased with increase in post treatment interval, being significantly higher at 7 DPT and lower at 3 DPT. After maximum exposure (7 days), Confidor and Jozer demonstrated a population reduction ranging between 85-90% for A. gossypii and 70-80% for A. devastans; however Bugatti, Blaster, Senator and Pouch explained less than 70% reduction in the population of these two insects. Almost all the evaluated insecticides described less than, 70% reduction in population of B. tabaci, T. tabaci, D. koenigii and O. hyalinipennis and proved less effective against these insects. The results of present study also indicated that Confidor and Jozer proved comparatively more effective against sucking insect pests. The results regarding the top-down effect of insecticides on beneficial insect revealed that Confidor, Jozer, Bugatti, Blaster and Senator demonstrated greater than or equal to 50% (50-90%) reduction in the population of ant, wasps, and coccinellid species and proved toxic while Pouch administrated less than 50% reduction in these beneficial insect and proved safe. Unlikely, all the evaluated insecticides demonstrated greater than or equal to 50 reduction in the population of C. carnea and proved toxic and harmful for this beneficial insect. Average of parasitism at 3 DPT and 7 DPT for all insecticides indicate that Confidor and Jozer demonstrated parasitism very close to that recorded in control at both post-treatment interval and proved comparatively safe for whitefly parasitism. The results of LC50 values indicate that Confidor was highly toxic for males, females and nymphs of D. koengii and O. hyalinipennis (LC50 ranged between 0.16-0.26%) followed by Jozer (LC50 ranged between 0.19-0.49%) and Pouch] (LC50 ranged between 0.46-0.92%). However, Bugatti demonstrated least toxicity for males, females and nymphs of D. koengii and O. hyalinipennis (LC50 ranged between 0.581.38%) followed by Blaster (LC50 ranged between 0.39-1.20%) and Senator (LC50 ranged between 0.47-1.17%).