Evaluation of a granular formulation containing Metarhizium brunneum F52 (Hypocreales: Clavicipitaceae) microsclerotia in controlling eggs of Aedes aegypti (Diptera: Culicidae)

We evaluated the potential of a granular formulation of Metarhizium brunneum F52 containing microsclerotia (MbMSc granules) for control of Aedes aegypti by targeting eggs. MbMSc granules produced infective conidia within 14 days after application to 2.5 g moist potting soil, producing 5.9 x 10(5), 2.08 x 10(6) and 6.85 x 10(6) conidia from 1, 5 and 25 mg MbMSc granules, respectively. Application of MbMSc triggered premature eclosion of eggs (EC50 = 12 mg) with percentages as high as 31 +/- 2.9% and 67 +/- 4.3% of the eggs treated with 5 and 25 mg MbMSc granules, respectively, after 14 days on moist filter paper. Premature eclosion of eggs started at 3 days subsequent to MbMSc granule application and survival of larvae was significantly reduced for granule treated eggs (74 +/- 2.2%, 39 +/- 2.0% and 23 +/- 4.9% larvae survived for 1, 5 and 25 mg granule treatments, respectively, EC50 = 4.9 mg). When MbMSc granules were applied in moist potting soil with mosquito eggs, rates of 1, 5 and 25 mg of MbMSc granules significantly reduced adult emergence with only 81 +/- 2.1%, 47 +/- 1.9%, and 34 +/- 2.1% emergence, respectively (EC50 = 7 mg). Eggs treated with increasing concentrations of fungal conidia enhanced premature eclosion of eggs with an EC50 = 1.6 x 10(6) conidia/mL. Our results demonstrate that MbMSc granules are a promising candidate for control of A. aegypti and that fermentative production of Mb F52 microsclerotia as the active propagule has the potential for use for mosquito control.