Effects of Entomopathogenic fungi and Bacillus thuringiensis‐based biopesticides on Spoladea recurvalis (Lepidoptera: Crambidae)
Du Plessis, H.
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Spoladea recurvalis (Fabricius) is one of the most devastating pests of amaranths caus- ing severe yield losses of 60%–100% to the crop. Unfortunately use of chemical pes- ticides is the most common control strategy that vegetable farmers rely on to control the pest. However, it is not effective and harmful to environmental and human health. Aiming to provide more environmentally friendly alternatives, this study evaluated the effects of various entomopathogenic fungal isolates and commercial based Bacillus thuringiensis Subsp. kurstaki product Halt ® , on the pest. Twenty- four en- tomopathogenic fungal (EPF) isolates from three genera (14 Metarhizium anisopliae, 9 Beauveria bassiana and 1 lsaria fumosorosea) were screened in the laboratory to as- sess their pathogenicity against second instar larvae of S. recurvalis. Only M. an- isopliae ICIPE 30 reached a moderate threshold, causing 58.3% larval mortality. All the 11 isolates (8 M. anisopliae, 2 B. bassiana and 1 l. fumosorosea) tested against adult S. recurvalis were pathogenic, with M. anisopliae ICIPE 30 and B. bassiana ICIPE 725 causing the highest mortality of 92% and 83%, respectively. Metarhizium anisopliae ICIPE 30 had the shortest LT 50 value of 4.8 days. Bacillus thuringiensis Subsp. kurstaki product Halt ® caused <50% mortality on S. recurvalis larvae. A consecutive applica- tion of M. anisopliae ICIPE 30 and Bt did not cause a significant increase in larval mortality compared to separate applications of both products. Results of this study suggest that M. anisopliae ICIPE 30 was the most potent candidate and could be used in an autodissemination approach for management of adult S. recurvalis