Higher volumes of conventional and novel chemical insecticides are applied by farmers to control resistant strains of armyworm ( Spodoperta litura ) in Pakistan without knowing their risks to the… Click to show full abstract
Higher volumes of conventional and novel chemical insecticides are applied by farmers to control resistant strains of armyworm ( Spodoperta litura ) in Pakistan without knowing their risks to the environment and to public health. Ten reduced-risk insecticides were tested for their compatibility with two entomopathogenic nematodes (EPNs); Heterorhabditis indica and Steinernema carpocapsae against S. litura . The insecticide emamectin benzoate was highly toxic (LC 50 = 2.97 mg/l) against 3 rd instar S. litura larvae when applied alone whereas, novaluron and methoxyfenozide were the least toxic (LC 50 = 29.56 mg/l and 21.06 mg/l), respectively. All the insecticides proved harmless against the two EPNs even 96 h after treatment. Indoxacarb, flubendiamide and spinetoram produced the greatest mortalities (72–76%) of S. litura larvae after 72 h when applied in mixtures with H. indica . Lowest mortalities (44.00 ± 3.74% and 48.00 ± 2.89) were observed for mixtures of H. indica with methoxyfenozide and chlorfenapyr, respectively. The positive control treatments with both EPNs ( S. carpocapsae and H. indica ) produced > 50% mortality 96 h after treatment. For insecticide mixtures with S. carpocapsae , only indoxacarb produced 90% mortality of larvae, whereas, indoxacarb, flubendiamide, emamectin benzoate, and spinetoram produced 90–92% mortality of larvae when applied in mixtures with H. indica . Additive interactions (Chi-square < 3.84) of EPN mixtures with reduced volumes of reduced-risk insecticides suggest opportunities to develop more environmentally favorable pest management programs for S. litura .
               
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