By Michelle Burns, CAHNRS MNEC intern, with additional reporting by Brian Clark and Nella Letizia
PULLMAN, Wash. Safe, cheap and effective alternatives for methyl bromide, long sought by nursery seedling growers and other farmers, may be on the horizon.
Ongoing research at Washington State University into antifungal plant species and a diagnostic test could help growers phase out their use of methyl bromide, a soil fumigant that kills fungal pathogens.
Methyl bromide the standard
Without methyl bromide or a viable alternative, some industries face extreme economic consequences. Conifer seedling growers, for example, will incur economically crippling losses to the pathogens methyl bromide helps control.
The Montreal Protocol, a treaty signed into law by the United States and 182 other countries in 1997, called for methyl bromide to be phased out by 2005. However, special use exemptions are still being given for agricultural sectors with no viable alternatives. The United States has obtained special use permits for various industries since 2005.
Brassica mustard alternative
Catherine Crosby, a doctoral student working with soil scientist Lynne Carpenter-Boggs of the WSU Center for Sustaining Agriculture and Natural Resources, is investigating the effectiveness of certain kinds of mustard as a methyl bromide alternative. The plants, members of the Brassica genus, are used in the production of biodiesel and as a green manure cover crop.
“Brassica seed meal and cover crops have antifungal properties that either kill or inhibit the growth of many organisms,” Crosby said. “The goal is to reduce or eliminate the need for methyl bromide and to avoid economic loss when special use permits stop being issued.” The application process for Brassica seed meal would be similar to that currently used to apply methyl bromide.
Detecting molecular damage
Another research component has just begun at the molecular level to detect the actual amount of harmful fungi in soil. Anna Leon, a plant pathology doctoral student, is working with WSU conifer expert and plant pathologist Gary Chastagner to develop a quick diagnostic test that can determine the level of a specific soil pathogen, Fusarium commune, in nursery soil.
A second part of this research includes pathogenicity trials to establish a threshold level at which F. commune causes disease. If growers can test for the number of fungal spores in soil, they can potentially reduce or eliminate fumigant applications.
“Giving growers a tool they can use to specifically test for one of the most detrimental pathogens they encounter will allow them to make more informed management decisions with regard to fumigation,” said Leon. “The goal of our research is to provide seedling growers with a realistic technology that will help them protect their bottom line while also moving away from the use of toxic chemicals.”
Will it work?
Will Brassica plantings coupled with a reliable and affordable method for the detection of harmful pathogens work as well as methyl bromide application? Chastagner sees this as the challenge of developing the new alternatives.
“Methyl bromide has been a valuable and highly effective soil fumigant used to kill soil-borne nematodes, fungal pathogens and weed seeds,” Chastagner explained. “While progress is being made to find economically viable and environmentally acceptable alternatives to this soil fumigant, the fact of the matter is that considerable work still needs to be done to insure that these alternatives are able to provide the control of soil-borne plant pathogens necessary for the production of high-value crops.”