M. KASHKOULI; N. POORJAVAD; J. KHAJEHALI
Abstract
Entomopathogenic nematode (EPN) combinations with other control agents are applied to obtain more desirable control of a pest by additive or synergistic effects on the pest mortality. ...
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Entomopathogenic nematode (EPN) combinations with other control agents are applied to obtain more desirable control of a pest by additive or synergistic effects on the pest mortality. In this study, the potential of EPNs (Steinernema carpocapsae, and Heterorhabditis bacteriophora) alone, chemical insecticides (imidacloprid, deltamethrin, and abamectin) alone, and EPN-insecticide combinations, against the onion thrips, Thrips tabaci (Thysanoptera: Thripidae) was investigated. In the first experiments, the effects of different concentrations of insecticides and EPNs on the thrips larvae were tested and the LC10 and LC30 values of insecticides were calculated. Then using a pre-treatment bioassay, the thrips larvae were treated with the EPNs at two concentrations, 400 or 1000 infective juveniles (IJs) per cm2, after they had been exposed to LC30 of abamectin (5.16 mg per litre (l), LC10 of imidacloprid (50.16 mg/l), or LC10 of deltamethrin (10.28 mg/l). Mortality percentages were recorded at different time intervals, 24, 48 and 72 hours after the EPNs utilization. Results showed that the sole application of EPNs caused less than 30% thrips mortality. The combination of H. bacteriophora and all insecticides interacted additively on the thrips mortality whereas imidacloprid treatment showed adverse effects on the efficacy of H. bacteriophora at 1000 IJs/cm2. Additive and synergistic interactions resulted in combining insecticides with S. carpocapsae. These combinations gave mostly higher thrips mortality than with EPN alone and synergistic interactions were observed in S. carpocapsae application at 400 IJs/cm2 with imidacloprid and deltamethrin and also at 1000 IJs/cm2 with abamectin.
