First report of Metarhizium anisopliae s.l. action on gastrointestinal ruminant nematodes in the free-living stage and its persistence in soil

ABSTRACT The fungus Metarhizium anisopliae is one of the most studied biological control agents in parasite control programs, especially when aiming the control of arthropods. Yet, studies using this biological agent to control gastrointestinal nematodes in ruminants are scarce. The present study evaluated the efficacy of the entomopathogenic fungus Metarhizium anisopliae sensu lato (s.l.) formulated in water and mineral oil on the free-living stages of gastrointestinal nematodes (GINs) in goats, by means of in vitro tests and in semi-natural conditions. The study also evaluated the persistence of the fungus in the soil. The experiments were constituted of four groups: control water; control oil; aqueous formulation of M. anisopliae s.l.; oil formulation of M. anisopliae s.l., each group consisting of 10 pots with Urochloa brizantha cv. MG5 grass. In the in vitro test, the groups treated with the aqueous and mineral oil formulation showed efficacy in controlling gastrointestinal nematodes of goats, providing a reduction of 45.5% and 43%, respectively, and a reduction varying from 36% to 77.9% and 42.6% to 90.2%, respectively, in the experiment under semi-natural conditions. Isolate M. anisopliae s.l. proved to be effective against goat’s gastrointestinal nematodes in the free-living stage, in both in vitro and semi-natural conditions tests, by significantly reducing the number of larvae with the formulations tested and remaining active for a period up to 52 days in the pots’soil. This study suggests the potential use of M. anisopliae s.l. for the biological control of gastrointestinal nematodes in ruminants.