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

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 sub tropics. 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.