Evaluation of Metarhizium anisopliae as a Biological Control for Wireworms

Todd Kabaluk, Mark Goettel, Bob Vernon and Christine Noronha

Pacific Agri-Food Research Centre
Lethbridge Research Centre

January 2001

Introduction
This report summarizes the results of experiments carried out in the year 2000 by Agriculture and Agri-Food Canada (AAFC) at the Pacific Agri-Food Research Centre (PARC; Agassiz) and the Lethbridge Research Centre (LRC). The purpose of the experiments was to assess the potential of the insect fungal pathogen Metarhizium anisopliae as a biological control agent for wireworms, particularly for Agriotes obscurus from British Columbia, although bioassays were also performed using an unidentified species of Limonius from Ontario. The research was prompted by the serendipitous discovery of M. anisopliae-infected wireworms during routine work associated with wireworm research at PARC in Agassiz in the summer, 1999. The research work summarized in this report involved both field and laboratory studies; the former carried out at PARC and the latter carried out at LRC.

M. anisopliae is well known for its ability to control pest insects. It has been developed into commercial products for use in several countries. A few examples include: Bio-Green and Bio-Cane granules for control of soil grubs of pasture and sugar cane in Australia, Green Muscle for control of locusts in Africa, Ago Biocontrol for control of various pests of ornamental crops in South America, and BioPath for control of cockroaches in the United States. In general, different strains of M. anisopliae are species specific, meaning that M. anisopliae found to infect one insect species will not necessarily infect other insect species. While this limits its use as a general pest control, it makes the fungus safer by limiting its effects on non-target organisms.

Immediately following the initial discovery of the fungus, preliminary experiments confirmed that the fungus could be isolated from- and reinfect wireworms so activities were carried out to further explore its potential as a biocontrol agent through research. During the winter 1999/2000, research plans were drafted, collaborating experts were identified, financial supporters were solicited, and a research permit was acquired from the Pest Management Regulatory Agency (PMRA). The Agassiz isolate was also mass-produced by Bio-Care Technology Ltd., Australia, into formulations and quantities suitable for field application. Field research work commenced in April 2000 and concluded September 2000. Laboratory research work commenced in the spring 2000 and concluded in October 2000.

The discovery of M. anisopliae on wireworms in 1999 was significant because reports on the occurrence of this fungus on wireworms are rare. There are a few reports from the early 1900's noting it's occurrence, however it is not known where or if the noted strains were preserved. In general, the research history of M. anisopliae as a wireworm control is sparse. Because of the discovery of the novel 'Agassiz' strain on wireworms, the reproducibility of infection, and the fact that the development of M. anisopliae control products for other insect pests has been successful, it was considered worthy to explore the Agassiz strain as a potential biological control for wireworms.

Figure 1. The Agassiz strain of M. anisopliae on wireworm cadavers. Shown is the progression from infection causing death (first worm) to mycelial growth (second worm) progressing to heavy sporulation.

Conclusions and Recommendations
The Agassiz strain of M. anisopliae to date is the strain most pathogenic to wireworms compared to two other stratins tested and will infect and kill wireworms under field conditions. M. anisopliae also has the potential to cause high (90% or greater) mortality to both A. obscurus and the unidentified species of Limonius under laboratory conditions. Wireworm mortality is enhanced when used in combination with Vitavax (lindane). Efficacy of M. anisopliae as measured by wireworm feeding damage to potato and corn was inconclusive in these studies.

Because high doses were required to kill a high proportion of wireworms in the laboratory, future experiments should be designed to mirror this effect. This would likely be achieved using either a wireworm attractant, such as wheat, to lure wireworms to areas of high spore concentrations, or position M. anisopliae granules or spores in the soil so that wireworms would pass through them in their normal patterns of movement (e.g. from lower soil layers to upper layers in the spring).

Because long periods were required for mortality to occur, other methods of using M. anisopliae for wireworm control should be considered. Perhaps a season long control effort throughout the summer or winter months would result in acceptable efficacy the following year.

Little is know about the environmental conditions under which the Agassiz isolate is most pathogenic. This should be studied in the laboratory as the information gained would ultimately translate into recommendations for its optimal performance in the field.

In developing M. anisopliae as a commercial control product, screening different isolates available from gene banks and evaluating the host range of M. anisopliae using other wireworm species and non-target organism should be pursued at all times.

In general, the ability of M. anisopliae to infect wireworms in the field, and the high potential for causing mortality as shown by incubated wireworms from the field and laboratory studies give sufficient reason to research the full potential of M. anisopliae as a biological control for wireworms.

Contact Information
Contact the following Agriculture and Agri-Food Canada researchers for information regarding this project.

• Todd Kabaluk, Project Leader Pacific Agri-Food Research Centre Box 1000 Agassiz, B.C.V0M 1A0ph. 604-796-2221 ext. 215fx. 604-796-0359 email: kabalukt@agr.gc.ca
• Dr. Mark Goettel Lethbridge Research Centre Box 3000 Lethbridge, ABT1J 4B1 ph. 403-317-2264 fx. 403-382-3156 email: goettel@agr.gc.ca
• Dr. Bob Vernon Pacific Agri-Food Research Centre Box 1000 Agassiz, B.C.V0M 1A0 ph. 604-796-2221 ext. 212fx. 604-796-0359 email: vernonbs@agr.gc.ca