Combined efficacy of insecticides and entomopathogenic nematodes in the management of cotton leaf worm Spodoptera littoralis
Combined efficacy of insecticides and entomopathogenic nematodes in the management of cotton leaf worm Spodoptera littoralis
H. M. Hassan† and S. A. Ibrahim
ABSTRACT
Effects of certain insecticides viz., Coragen, Nomolt, Ekio and Magic smart with two species of entomopathogenic nematodes, Steinernema carpocapsae and Heterorhabditis bacteriophora were tested against cotton leaf worm Spodoptera littoralis. All tested insecticides caused less mortality to the tested entomopathogenic nematodes. Magic smart significantly surpassed other insecticides causing the mortality of 11.6 and 13.8 % to the entomopathogenic nematodes S. carpocapsae and H. bacteriophora, respectively as compared to Coragen that caused slight mortality, 2.5 and 4.4%, respectively and did not differ significantly than the check. Nomolt and Ekio caused 5.4 and 8.8 % mortality of S. carpocapsae as well as 8.8 and 12.0 % to H. bacteriophora, respectively. These results show that the tested insecticides have less effect on entomopathogenic nematodes especially S. carpocapsae. S. carpocapsae exposed to Coragen, Nomolt, Ekio and Magic smart resulted in 5th instar larval mortality of cotton leaf worm by 92.5, 85.0, 80.0 and 75.0 %, respectively whereas H. bacteriophora caused mortality by 83.4, 77.2, 71.0 and 60.6 %, respectively. The experimental findings showed that combined efficacy of S. carpocapsae or H. bacteriophora with either of the insecticides viz., Coragen, Nomolt, Ekio and Magic smart at the quarter lethal concentration (LC25) is effective in causing mortality of S. littoralis.
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