Ecotoxicological hazards of herbicides on biological attributes of Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae).

Ecotoxic effects of commonly used herbicides i.e. glyphosate, atrazine, metribuzin, alachlor and 2, 4-D were evaluated on the biological and demographic parameters of Zygogramma bicolorata Pallister on parthenium in laboratory. The herbicides used in the bioassay were within a minimum range of their recommended field dose. In direct toxicity experiment, 2,4-D and alachlor caused the highest mortality of 3rd instars and prolonged the development time. Fecundity and eggs viability were also significantly reduced in all treatments. Indirect toxicity (carryover effect) was evaluated through life table analysis of F1 progenies developed from surviving 3rd instars treated for direct toxicity experiment. Incubation period and overall development time was considerably prolonged in all treatments especially in 2, 4-D treated group. Daily fecundity and population growth parameters were significantly lowest in 2, 4-D treated groups compared to other tested herbicides. A significantly greater number of females were produced in glyphosate treatment than other treatments. Based on the present study, none of the tested herbicide can be classified as safe to Zygogramma bicolorata, while glyphosate was found to be least toxic. Therefore, it can be concluded that application of field recommended dose of glyphosate might be used in integration with Z. bicolorata for effective management of parthenium, however this needs to be conducted under natural field conditions.