Elsevier

Acta Tropica

Volume 193, May 2019, Pages 192-198
Acta Tropica

Activity of additives and their effect in formulations of Metarhizium anisopliae s.l. IP 46 against Aedes aegypti adults and on post mortem conidiogenesis

https://doi.org/10.1016/j.actatropica.2019.03.002Get rights and content
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Highlights

  • Metarhizium anisopliae s.l. IP 46 highly active against Aedes aegypti adults.

  • activity improved by diatomaceous earth combined with oil.

  • shorter exposure times did not reduce efficacy of formulates.

  • IP 46 conidia formulated with mineral oil and diatomaceous earth most promising.

  • additives tested without clear effect on quantitative conidiogenesis on cadavers.

Abstract

Background

Oil formulations of entomopathogenic fungi have interest for biological mosquito control.

Objectives

The activities of M. anisopliae s.l. IP 46 conidia were tested in Aedes aegypti adults either without any formulation or formulated with vegetable or mineral oil and in combination with diatomaceous earth.

Findings

IP 46 was highly active against adults, the vector of important arboviruses in the tropics and subtropics. At an exposure of adults to 3.3 × 107 conidia/cm2, values of lethal times TL50 and TL90 reached minimal 3.8 and 4.6 days, respectively, and lethal concentrations LC50 and LC90 were 2.7 × 105 and 2.4 × 106 conidia/cm2, respectively, after 10 days of exposure. Activity against adults was improved by diatomaceous earth (KeepDry® KD) combined with mineral oil (Naturol® N) or vegetable oil (Graxol® G). Additives KD or N separately (and G to a lesser extent) or in combination, KD + N and KD + G without conidia had also a clear adulticidal effect. Efficacy of conidia formulated or not with KD + N decreased somewhat at shorter exposure periods. Time of exposure (0.017, 12, 48, 72 or 120 h) of adults to KD and N or IP 46 or conidia and KD and N had no significant effect on mortality. M. anisopliae s.l. recycled on fungus-killed mosquitoes producing high quantities of new conidia regardless of the conidial concentrations or formulations tested. Additives tested had no clear effect on quantitative conidiogenesis on cadavers.

Main conclusions

Formulations of IP 46 conidia with mineral oil and diatomaceous earth represent a promising tool for the development of potent strategies of focal control of this important vector with entomopathogenic fungi.

Keywords

Entomopathogenic fungus
Mosquito
Mineral oil
Vegetable oil
Diatomaceous earth

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