Spinosad Interacts Synergistically with the Insect Pathogen Metarhizium anisopliae Against the Exotic Wireworms Agriotes lineatus and Agriotes obscurus (Coleoptera: Elateridae)

Abstract

We determined that spinosad interacts synergistically with the biocontrol agent Metarhizium anisopliae (Metch) Sorokin to increase the mortality of two wild-collected wireworm species, Agriotes lineatus (L.), and Agriotes obscurus (L.). Bioassays were performed using a M. anisopliae isolate originally acquired from a local wireworm cadaver. M. anisopliae was applied as a soil drench at 3.3 x 10(2) and 10(4) conidia per gram sand, respectively. Soil drenches also were prepared using a commercial formulation of the actinomycete toxins spinosyn-A and spinosyn-D (common name spinosad) at sublethal doses of 1.5, 3, and 6 ppm active ingredient per gram sand. Combined treatments of spinosad and M. anisopliae were synergistic in causing mortality for all spinosad concentrations. Wireworm feeding activity was reduced after exposure to both spinosad and M. anisopliae and was found to be concentration dependent. The high mortality and reduced rate of wireworm feeding suggest that spinosad and M. anisopliae treatment combinations should be tested in the field.

Natural and released inoculum levels of entomopathogenic fungal biocontrol agents in soil in relation to risk assessment and in accordance with EU regulations

“…Chemicals can make insects more susceptible to EPF even when used at relatively low doses (Quintela and McCoy 1998;Ericsson, Kabaluk, Goettel, and Myers 2007;Shah et al 2007a). Chemical insecticides may influence insect behaviour such as reduced preening which prevents removal of spores and increased movement, which increases acquisition of inoculum (Shah et al 2007a;Butt et al unpublished observations).…”

Fungal infection counters insecticide resistance in African malaria mosquitoes

“…Studies on insect hosts other than mosquitoes have indicated that fungal infection can act synergistically with insecticides, increasing the impact of otherwise sublethal insecticide doses (24)(25)(26). Mixtures of M. anisopliae and deltamethrin were shown to enhance virulence of both components when tested against ticks, indicating synergistic effects that would enhance the effectiveness of low fungi and insecticide concentrations (27).…”

Interaction between pesticides and other factors in effects on bees

“…Asian long-horned beetles treated with imidacloprid produced significantly fewer Metarhizium conidia compared to beetles not treated with imidacloprid (Russell et al, 2010). Similar synergism was observed in wireworms (Ericsson et al, 2007). Cockroaches (Blatella germanica) were killed significantly faster when fed on imidacloprid or propetamphos after a topical application of M anisopliae whereas chlorpyrifos and cyfluthrin were additive (Neves et al, 2002).…”