Risk assessment of neonicotinoids applied to coffee ecosystem

Laboratory derived toxicity data was used to predict the toxicity of neonicotinoids, viz., thiamethoxam and imidacloprid to beneficial arthropods in a coffee ecosystem. The beneficial insects included the Indian honey bee, Apis indica (Fb.), the Italian bee, Apis mellifera (Linn.), the little bee, Apis florea (Fb.) and the dammer bee, Trigona irridipenis (Smith). Two commonly occurring sucking pests of coffee, viz., coffee green scale, Coccus viridis (Green) and the black citrus aphid, Toxoptera aurantii (Boyer de Fonscolombe) were also included in the study to compute the selectivity ratio to these beneficial organisms. The toxicity of the chemicals to all the insects ranged from 0.00000076 to 0.0061 micrograms per insect for thiamethoxam and 0.00000122 to 0.0026 micrograms per insect for imidacloprid respectively. Though, the probit substitution method predicted the recommendation of thiamethoxam preferably, both thiamethoxam and imidacloprid could be used as one of the IPM components based on the values for selectivity ratio. Considering the sequential testing scheme and hazard ratios, appropriate timing and selective method of application like stem application is suggested to safeguard honey bees.