Got nematode troubles? Fungi? Too many weeds in a field? Spread some mustard on them.
The Agricultural Research Service at the United States Department of Agriculture has teamed up with university scientists to study mustards as an alternative to chemical pest control.
But scientists aren’t smearing pests with mustard that comes in a jar.
Rather, they’re biofumigating pests with stands of white mustard, brown mustard, and rapeseed-members of the Brassica plant family.
Biofumigation refers to natural substances plants release while decomposing that make surrounding soils toxic to some weeds, nematodes and fungi.
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Experiments performed in Washington state dovetail with increasing grower interest in mustard crops for pest control and as green manure, meaning it can be disked into soil to improve tilth, organic matter, aeration and water filtration.
Despite such benefits, there’s still much to learn about how mustards control pests and under what conditions they work best, notes ARS agronomist Rick Boydston, study co-ordinator since 2000.
Much credit for mustard’s biofumigant effect against soilborne pests is given to isothiocyanates, or ITCs, chemical byproducts of the plants’ decomposition. But scientists suspect ITCs are only one piece of the pest-control puzzle.
“There’s a lot going on there that we don’t know about,” said Boydston at ARS’s Vegetable and Forage Research Unit in Prosser, Washington.
A chief question is whether nematodes, weed seeds or fungi die from direct contact with ITCs or as a result of other chemical or biological changes in soil.
To find out, Boydston is collaborating with a multidisciplinary team that includes a soil scientist, microbiologist, chemist and agricultural systems educator.
With such wide-ranging expertise, the team can examine many facets of mustard cover crops that growers have neither the time nor resources for.
“Growers are probably more focused on nematode suppression and wind erosion control. But our group can measure disease incidence, nematodes, weeds and soil micro-organisms,” he said. “We’re looking at multiple problems and benefits.”
The resulting information could lead to new cropping systems that use mustards better-or pinpoint their limitations. Another possible spinoff could be development of new mustard cultivars custom-bred for specific uses, such as anchoring soil or biofumigating it.
