Safety of insecticidal sprays to spider and predatory coccinellids in varied rice cultivation system

Abstract

Insect pests and diseases impede the attainment of higher yields by conventional transplantation methods in rice crop. However, planting methods ence, different planting methods viz., broadcasting and drumsowing and plant protection methods viz., organic protection practises are gaining popularity in our country. However, the effect of such planting methods and plant protection practices on various predators in the field has to be assessed. Since literature on the effect of different planting methods and plant protection methods on Coccinellid predators is scant, the present study was undertaken to understand the impact of these methods on the abundance and diversity of Coccinellids. The experiment was laid out in College Farm, Rajendranagar during kharif 2014-15 and 2015-16 with three main treatments viz., Transplanted rice, broadcasted rice and drumsown rice. Under each module, three types of plant protection measures viz., organic protection, farmers’ practices and “no protection”. Six species of Coccinellids were recorded during the study, viz., Micraspis, Harmonia, Cheilomenes, Propylea dissecta, Coccinella and Scymnus. Population of Coccinellids was more in organic protection plots and ‘no protection’ plots compared to farmers’ practices plots. Similarly, broadcasted plots recorded higher populations of beetles than transplanted and drumsown plots in general, though interaction effects were also significant. Diversity study of Coccinellids revealed that species richness was 7 in all the varied cultivation methods and plant protection practices and it seemed to be least affected by the main treatment (cultivation type) or the sub-treatment (plant protection practises) followed. Shannon’s species diversity index however, varied among cultivation techniques and the plant protection practices and it ranged between 0.91 -1.14 indicating a fairly stable population, though not very stable