Environmental and Behavioral Constraints on the Infection of Wireworms by Metarhizium anisopliae

Abstract

Environmental and behavioral factors that affect the infection of wireworms [Agriotes obscurus L. (Coleoptera: Elateridae)] by a unique isolate of Metarhizium anisopliae Sorokin (Hypocreales: Clavicipitaceae) were studied. After wireworms were placed in soil containing 10(6) M. anisopliae conidia/g and incubated at 6, 12, or 18 degrees C, significant disease development and wireworm mortality occurred only in those wireworms incubated at 18 degrees C. At this temperature, mortality was found to be dependant on the time exposed to the contaminated soil, and a minimum exposure time of 48 h was required to cause significant levels of mortality. Despite the restrictive effect of cooler temperatures on disease development and mortality, infected wireworms did not choose temperatures that inhibited disease development when given the opportunity to do so in a separate experiment. Finally, wireworms were repelled by M. anisopliae-contaminated soil at a rate that increased with the soil conidia concentration, but the rate of emigration was reduced when a food source was present. The results of this study indicate that factors including temperature, time exposed to M. anisopliae, conidia soil concentration, and food availability will affect mortality rates of wireworms and are likely to affect field performance of M. anisopliae as a biological control.

New perspectives on insect pathogens

“…The genus Metarhizium contains biologically distinct subtypes with wide insect host ranges, e.g., Metarhizium robertsii [formerly known as Metarhizium ani- abilities to form associations with different plant species (Bidochka et al, 2001;Fisher et al, 2010). Overall, the effects of Metarhizium on plants are favorable as application of conidia to corn seeds significantly increased yields (Kabaluk and Ericsson, 2007), and the fertility of soils treated with some Metarhizium strains can be improved beyond insect control (unpublished data), but there is very little data as to the ecological consequences of these interactions. The fact that many genotypes of Metarhizium appear to be specialized to different plants (Fisher et al, 2010), suggests that the impact of rhizosphere competence by Metarhizium on plant ecology in general could be considerable with implicit co-evolutionary implications.…”

Preventive application of an entomopathogenic fungus in cover crops for wireworm control

“…It has been shown that lower temperatures slow down fungal infections of wireworms (Kabaluk and Ericsson 2007). Accordingly, an EPF application during summertime in the northern hemisphere, as performed in our experiment, should promote fungal growth and efficacy.…”

“…This stimulated research aimed at the development of ecologically acceptable control methods (Ester and Huiting 2007;Kabaluk et al 2005;Kleespies et al 2013;Kölliker et al 2011;Ladurner et al 2009). Among the natural enemies of wireworms, entomopathogenic fungi (EPF), especially those in the genus Metarhizium Sorokin (Hypocreales: Clavicipitaceae), are currently regarded as the most promising for wireworm control (Ansari et al 2009;Eckard et al 2014;Kabaluk 2007;Kabaluk and Ericsson 2007;Kölliker et al 2011). …”

Scientific support, literature review and data collection and analysis for risk assessment on microbial organisms used as active substance in plant protection products –Lot 1 Environmental Risk characterisation

“…There was neither correlation between soil type and efficiency nor between soil type and conidial viabilities. Similarly, Kabaluk et al (2007) observed that efficacy of M. anisopliae for wireworms differed significantly among sand, clay, and organic soils at the same moisture level. In another study, B. bassiana killed more ants in silt (70:15:15, silt: sand:clay) and in sandy soil (15:70:15) than in clay (15:15:70, as in the control) (Fuxa et al, 2004).…”