Effects of different formulations on viability and medium-term storage of Metarhizium anisopliae conidia

Abstract

The aim of this work was to evaluate the effects of different formulations on the viability of Metarhizium anisopliae conidia. In a first experiment, the viability of conidia mixed with eight emulsifiable adjuvant oils (EAO), seven wetter/spreaders, three vegetable oils and four mineral oils was evaluated 24h and 48h after spreading over SDA medium surface. Some formulations, which did not present any adverse effect on conidial viability in the first 24h of incubation, were recommended for the medium-term storage experiment. In a second experiment, the effects of different formulations on medium-term storage (40 weeks) of M. anisopliae var. acridum conidia were evaluated at 10oC and 27oC. Five EAO, one vegetable oil, a mixture of mineral oils and pure dry conidia were tested. In the experiment 1, the oil formulations did not cause any negative effect on conidial germination. The treatments with the adjuvant oils Actipronâ, Ashladeâ and Codacideâ gave germination levels equal to mineral and vegetable oils after 24h of incubation. The wetter/spreader Ethokenâ C12 was lethal to conidia. All tested emulsifiable adjuvant oil-based formulations were compatible to the conidia as the oil-based formulations after 48h of incubation. In the experiment 2, conidial viability within the same formulation declined over time. Conidial viability was maintained above 90% at 10oC in all tested formulants. The conidial suspension with Ashladeâ gave equal germination levels to Shellsol plus Ondina, when stored at 10oC and 27oC for 40 weeks. Thus EAO can be used to formulate M. anisopliae conidia without adverse effects on viability.