Effect of chemical vis-a-vis non-chemical pest management on predatory spiders in paddy-ecosystem

Abstract

Spiders act as one of the most important defenders in paddy ecosystem and there are several families of those with different habits. The question on the effect of chemical application in comparison to the non chemical option on different spider families in the zone under study was attempted for getting answer. For that purpose, the field experiment was conducted during kharif, 2014 for studying spider abundance in chemical versus non-chemical treatments. Chemical based treatment consisted of the application of Phorate 10G at 10 days after transplanting (DAT), followed by spraying with Imidacloprid 17.8 SL at 45 DAT, and dusting of Methyl Parathion 2D at 80 DAT. Transplanting of rice following skip row technique, sowing of okra, cowpea, sesame & balsam on the surrounding bunds, retention of weeds on the bunds, single inoculative release of Trichogramma chilonis @ 1,00,000 at 35 DAT, and use of pheromone (Scirpophaga incertulus lure)-cum -light trap @ 10 traps ha^-1 were integrated together in nonchemical based treatment. The results revealed that the population of wolf spiders and long jawed spiders were statistically higher during all the seven dates of observation in non-chemical based approach. Amongst Araneid spiders, non-chemical based approach recorded significantly higher population at 60, 75 and 90 DAT. On the basis of overall mean, the non-chemical treatment had significantly higher population of spiders belonging to most of the families except Thomisidae. The mean population of spiders across the families varied from 1.06 to 12.0 and 0.54 to 6.66 per double sweep per sub plot in non-chemical based and chemical based treatment, respectively. Thus, the study confirms the safety of the non-chemical based approach in maintaining significantly higher level of spider population.