Evaluation of non-target safety of a native fungal biocontrol agent under development for control of grasshoppers in pulses and other crops

Project Code BPI07-190

Project Lead

Dan Johnson  University of Lethbridge

Objective

To evaluate the environmental safety of a strain of Metarhizium anisopliae isolated from Canadian soil and developed for grasshopper control, determine impacts on selected non-pest insects, complete data requirements for registration submission to PMRA, and to develop a commercialization strategy for the product

Summary of Results

Background

Grasshopper outbreaks are a serious threat to many food and forage crops in Canada. To manage grasshoppers, growers continue to rely on chemical insecticides, primarily organophosphates, carbamates, and pyrethroids. However, some of the organophosphate and carbamate products are under regulatory re-evaluation. Alternative tools are needed to diversify the control methods and allow for an integrated pest management strategy that will reduce risks to human health and environment.

An indigenous fungus, Metarhizium anisopliae, discovered in Canadian Prairie (Alberta) soil is being developed as a microbial control agent for grasshoppers. This fungus is related to other Metarhizium strains that have been registered for biological control of grasshoppers and locusts in Africa and Australia. The native organism Metarhizium anisopliae strain S54 can be distinguished from other Metarhizium species or variants by molecular-based methods. This allows monitoring the fungus in a variety of environmental substrates such as soil, crops, water or even in pest and beneficial insects present in the treated vegetation.

This single year project aimed to experimentally determine the safety of the native isolate Metarhizium anisopliae strain S54 to beneficial and non-pest insects, as well as fulfill some key requirements in support of registration of the fungus as a microbial pest control agent in Canada.

Approach

The study was carried out in 2007/2008 at the University of Lethbridge in Alberta. Sensitivity of nineteen selected non-target/beneficial terrestrial and aquatic arthropod species (and some new potential target pest species) to the native fungus S54 was tested under laboratory conditions. Included among the terrestrial arthropods tested were: Coccinella septempunctata, Trichomalopsis sarcophagae, Tenebrio molitor, Harpalus funerarius and Amara littoralis; included among aquatic arthropods tested were: Gammarus pulex, Notonecta undulate and Chaoborus americanus.

Fungal pathogenicity to these species was evaluated by testing infectivity and virulence levels following certain time intervals from treatments with various concentrations of fungal spore suspensions (e.g. ranging from 0, 1.5x104, 3.0x104, or 1.2x105 per ml) of Metarhizium anisopliae var. anisopliae isolate S54. Mortality rates and incidence of fungal sporulation on insect cadavers was monitored.

Results

Possible sensitivity of some of the tested non-target arthropods to S54 was detected in the laboratory, whereas no concern was identified for others.

Terrestrial arthropods

High mortality of the non-target coccinellid species, C. septempunctata at moderate to high doses, but upon further examination, it was found that the test insects may have been weakened by parasitoids and other fungal pathogens. This suggests that the observed high mortality may not have been caused by M. anisopliae alone.

A further tested non-target arthropod species, T. molitor is not likely to be susceptible to the fungal isolate based in data from this project. Similarly, no infection was observed in two treated carabid species, H. funerarius and A. littoralis. Slightly elevated but not significantly different mortality was observed in treated E. pennsylvanica.

Aquatic arthropod

Preliminary results suggest that the aquatic amphipod, G. pulex, and dipteran, C. americanus would not be expected to be significantly affected by exposure to S54 spores accidentally introduced in bodies of water. In contrast, results with non-target aquatic beetles in the families Notonectidae and Dytiscidae suggest that aquatic backswimmers and diving beetles may be susceptible to infection by this fungal agent.

Other potential pest targets

The potential to control other insect pest species including cabbage seedpod weevil, pea leaf weevil, cabbage root fly and a blister beetle with S54 was also demonstrated based on in vitro tests, but dose-response relationships were not established to determine if this could be transferred to the field.

Regulatory implications

A pre-submission consultation was held with the PMRA in 2011 based on data from this project. It was suggested that any remaining environmental toxicology data requirements can be addressed with existing information and scientific rationales, and that there is sufficient evidence on the efficacy of the product to proceed with a submission.

This project, therefore, contributed to the completion of an important portion of the regulatory data package for this highly promising organism for the sustainable control of grasshoppers. Efforts to commercialize the product are on-going, and it is anticipated that marketing of this product would significantly contribute to reducing pesticide risk to human and environmental health.

For more information please contact Dr. Dan Johnson.

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