Biofumigation as an IPM Strategy

Biofumigation as an IPM Strategy

Summary

Managed decomposition of crop residue, biofumigation, is a biointensive strategy that has the potential to reduce the use of toxic biocides used to kill soilborne pathogens. Our study system is the early dying disease of potato (PED) caused by the fungus Verticillium dahliae and the root lesion nematode Pratylenchus spp. Potato early dying is a serious and chronic problem everywhere potatoes are grown and is currently managed using soil fumigation.

In 2007 we conducted an experiment to compare rapeseed, a standard biofumigant cover crop, and forage pearl millet, a cover crop with no known biofumigant properties, with and without solarization. for suppression of PED pathogens. Forage pearl millet was superior to rapeseed for nematode suppression, most likely due to the excellent host status of rapeseed for nematode reproduction. We worked with 12 growers to conduct their own experiments comparing forage pearl millet to commercial mixtures of Brassica spp. reported to have biofumigation properties successful in potato cropping systems. The crops were planted in replicated strips in August, 2007 and incorporated as a green manure in October, 2008. Other cover crops included in the trials were oat and various legumes. Despite above-normal temperatures in October and November, the millet was killed by frost, showing that this crop is not suitable as a late summer cover crop in Wisconsin. Four presentations about cover crops and soil health were presented to growers in 2007. We used audience response systems in a meeting of 125 growers to survey their attitudes and practices. Their responses indicated an understanding of biofumigation, but a reluctance to replace soil fumigation with synthetic pesticides.

Objectives/Performance Targets

Build a knowledge base among growers and agribusiness representatives about ecosystem services available in the soil and the organisms involved.

Increase the expertise of farmers about cover crop management and the practice of biofumigation.

Increase awareness of farmers, crop consultants, county agents and industry representatives of the value of biofumigation relative to soil fumigation with synthetic chemicals.

Accomplishments/Milestones

Conducted an experiment comparing forage pearl millet with rapeseed, with and without solarization, for suppression of root lesion nematodes and Verticillium.

Provided seed of forage pearl millet to 12 growers for on-farm tests comparing millet to other cover crops, including commercial biofumigant mixtures.

Conducted assays of nematodes and Verticillium dahliae for the on-farm trials to establish pretreatment baseline values.

Conducted two meetings to present information to growers (attendance = 20 for each meeting).
Used audience response systems at Wisconsin’s Annual Potato Meeting (125 attendees) to engage growers in a discussion about the potato early dying disease and fumigation alternatives.

Impacts and Contributions/Outcomes

We increased awareness and knowledge about cover crops and biofumigation for the management of potato early dying. Wisconsin growers were not familiar with forage pearl millet, a crop that is gaining attention nationally for suppression of root lesion nematodes. Forage pearl millet has the potential for relatively high biomass, but is a poor host for the root lesion nematode species involved in the potato early dying disease. Our on-farm trials revealed that this cover crop will have to be planted early in the summer in Wisconsin.

In a meeting with over one hundred potato growers, biofumigation was presented as a measure to reduce or delay soil fumigation with synthetic pesticides. Information about when biofumigation is appropriate was presented. Questions about cover crops and biofumigation indicated that we were successful in drawing attention to this biologically based strategy for disease management.

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