An indigenous Metarhizium sp. strain amended in compost enhances sweetpotato growing system and management of Cylas formicarius (Coleoptera: Curculionidae)
摘要
Two commercial products, Botanigard® (active agent Beauveria bassiana Vuillemin [Hypocreales: Cordycipitaceae]) and Met Master® (active agent Metarhizium anisopliae [Metchnikoff] Sorokin [Hypocreales: Clavicipitaceae]), and a Hawaiian isolate of Metarhizium anisopliae Ko-002 were evaluated for managing sweetpotato weevil, Cylas formicarius Fabricus (Coleoptera: Brentidae). Choice arena tests indicated M. anisopliae Ko-002 neither attracted nor repelled C. formicarius but did suppress the insect’s feeding. In the greenhouse, inoculation with M. anisopliae Ko-002 enhanced sweetpotato growth. Virulence of commercial products against C. formicarius larvae were tested in the laboratory. Met Master® did not result in any C. formicarius larvae mortality while Botanigard® resulted in 30% mortality of the insects. Field plots treated with Botanigard® resulted in lower sweetpotato yield, no change in C. formicarius damage, and did not lower sweetpotato weevil population density compared to the untreated control. The Botanigard® may have had unintended effects on natural predators of C. formicarius. Met Master® had no effect on sweetpotato yield, C. formicarius damage, nor sweetpotato population density as compared to the untreated control. Metarhizium anisopliae Ko-002, applied as a compost amendment at planting, did not affect sweetpotato yield, but reduced C. formicarius damage, and lowered sweetpotato weevil population density. Field plots amended with Metarhizium anisopliae Ko-002 had higher plant vigor ratings and were taller than plants in unamended plots. Entomopathogenic fungi, especially the locally isolated M. anisopliae, can improve management of the C. formicarius and enhance plant growth when incorporated as a compost amendment.