International Journal of Tropical Insect Science (2015) 35, 153-163

Ronnie Dotaona, Bree A.L. Wilson, Mark M. Stevens, Joanne Holloway and Gavin J. Ash (2015)
Screening of tropical isolates of Metarhizium anisopliae (Hypocreales: Clavicipitaceae) for virulence to the sweet potato weevil, Cylas formicarius (Coleoptera: Brentidae)
International Journal of Tropical Insect Science 35 (4), 153-163
Abstract: The sweet potato weevil (SPW), Cylas formicarius, is a serious pest of sweet potato in Australia and Papua New Guinea. Ten strains of Metarhizium sp. isolated from Australian soil samples were evaluated for their growth characteristics and screened for virulence to adult SPW under laboratory conditions. All isolates except QD62 (48.6%) had moderate to high germination (66–97%), and all took 2 to 4 days to sporulate at 25 °C. The optimal temperature for radial growth for the majority of isolates was 30 °C, and there was a significant interaction between isolate and temperature (P< 0.05). Isolate QS155 showed the fastest radial growth at 30 °C. The internal transcribed spacer sequences showed slight variations among the isolates; however, all isolates were shown to be Metarhizium anisopliae. Isolates varied greatly in their virulence. At 10 days after inoculation (DAI) by immersion in a suspension of 1 × 10⁷conidia/ml, 9 of the 10 isolates were virulent, causing 80–100% mortality of adult SPW. Only two isolates (QS001-6 and QS155) caused more than 50% mortality at 5 DAI. In dose-mortality bioassays, isolate QS155 had the lowest 20-day LC₅₀ and LC₉₀ values; however, there were no statistically significant differences in mortality among the three most promising isolates tested (QD66, QS001-6 and QS155). These results show that M. anisopliae isolate QS155 has potential as a microbial control agent for SPW, and that further evaluation under glasshouse and field conditions is warranted.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Mark M. Stevens, Jo Holloway, Gavin J. Ash

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
evaluation - screening - selection

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Cylas formicarius	Sweet potato (Ipomoea batatas)	Papua New Guinea
	Cylas formicarius	Sweet potato (Ipomoea batatas)	Australia (NT+QLD)
Metarhizium anisopliae (entomopathogen)	Cylas formicarius	Sweet potato (Ipomoea batatas)