Submitted to: Journal of the American Mosquito Control Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2017
Publication Date: 8/31/2017
Publication URL: http://handle.nal.usda.gov/10113/5922778
Citation: Weiler, L., Rooney, A.P., Behle, R.W., Muturi, E.J. 2017. Characterization of Tolypocladium cylindrosporum (Hypocreales: Ophiocordycipitacea) and its impact against Aedes aegypti and Aedes albopictus eggs at low temperature. Journal of the American Mosquito Control Association. 33(3):184-192.
Interpretive Summary: Control strategies employed for mosquitoes mostly target larvae and adult stages using insecticides. Beneficial microbial agents like fungi are explored and utilized to control mosquitoes. The purpose of this study was to characterize the fungus Tolypocladium cylindrosporum IBT 41712 strain and studied its potential to infect eggs of container inhabiting mosquitoes Ae. aegypti and Ae. albopictus at low temperature. Eggs of these mosquitoes are capable of surviving for long period of time and can undergo diapause allowing them to overwinter in temperate climates. Tolypocladium cylindrosporum is a potential mosquito control agent for eggs that overwinter or undergo long diapause.
Technical Abstract: We examined the growth characteristics of Tolypocladium cylindrosporum IBT 41712 and its potential to infect eggs of Aedes aegypti Linnaeus and Aedes albopictus (Skuse) mosquitoes at low temperature (15 deg C). When grown on sabouraud dextrose agar supplemented with yeast extract, IBT 41712 formed white colonies turning creamy white when mature. The mycelia bore swollen conidiophores producing smooth-walled, oblong to cylindrical conidia with varying size, ranging from 1.5µm to 3.5µm long. The optimum temperature for growth was 28 deg C with a maximum diametric growth rate of 2.1 ± 0.05 mm/day and sporulation occurred 8-10 days. There was no fungal growth observed above 33 deg C, but growth was observed down to 4 deg C. Fungus treated mosquito eggs hatched early even when eggs were on solid media and this effect was more pronounced in Ae. aegypti compared to Ae. albopictus. At 21 days post treatment, survival of both Ae. aegypti (control = 91%, 1 × 107 conidia/mL fungal treatment = 0%) and Ae. albopictus (control = 85%, fungal treatment = 28%) larvae were significantly lower in fungal treatment compared to the controls. IBT 41712 successfully infected mosquito eggs at 15 deg C. Premature hatching of fungus-treated eggs increased the vulnerability of newly hatched larvae to infection by the fungus. The ability of the strain to grow in a wide temperature range and effectively infect mosquito eggs at low temperature warrants further investigation for its potential as mosquito control agent targeting eggs that overwinter or undergo long diapause.