NCSU Transition Team for Methyl Bromide helps growers maintain yields while improving the ozone layer

A group of extension specialists at NC State University have helped growers use integrated pest management to transition away from a toxic fumigant while maintaining their yields. Decreased use of the fumigant has had positive environmental consequences as well: the decreased use has led to lower bromine levels in the atmosphere, accounting for one-third of the measured decrease in ozone depleting halogens above the Antarctica.

The transition away from the pesticide methyl bromide began in 2005, in response to scientific data linking it to decreasing ozone levels in the atmosphere. Developed countries banned methyl bromide under the Montreal Protocol, an international treaty signed in 1987 to protect the stratospheric ozone layer. In the United States, the USDA National Institute for Food and Agriculture devised a funding mechanism to help scientists gradually wean farmers away from methyl bromide use. Each year, scientists would apply for “critical use exemptions” to specify how much methyl bromide they felt farmers in their state would need while they searched for alternatives. The funding mechanism was called the “Methyl Bromide Alternatives Program.”

NC State Personnel install an on-farm-research tomato trial in western NC in May 2017

NC State Personnel install an on-farm-research tomato trial in western NC in May 2017

Methyl bromide is a fumigant used in strawberry and vegetable production that prevents plant pathogens and controls weeds. It was an inexpensive and effective way to take care of pest management issues in general, and research revealed that nothing existed to take its place on a one to one basis. Solutions involved taking an integrated approach to pest management and addressing insect, disease and weed problems separately rather than using the uniform approach that methyl bromide afforded.

From 2005 to 2012, extension personnel submitted critical use exemption requests to the EPA to prevent growers from being left with no options for pest and disease control. Each year, the amount of methyl bromide available for use would decrease, forcing growers to look into alternatives. Surveys done by extension personnel early in the process revealed that growers were reluctant to try different methods because of the perceived risk.

The NC State working group, comprised of entomologists, plant pathologists, agricultural economists and weed scientists experimented with several combinations of drip and fumigant pesticides, combined with tactics to improve soil health before planting and materials to cover the ground after planting and while fumigating. Specialists focused on pest management in strawberry, tomatoes and peppers.

Multiple research trials with all three crops revealed specific management recommendations for each. For strawberries, for instance, individual fungicide applications applied through drip irrigation was not as effective as fumigated treatment, which increased yields up to 50 percent as opposed to 8 percent with irrigation, compared to no soil treatments. Drip irrigation for herbicides was effective in tomato and pepper, however.

A report on impacts of the multi-year research and extension project showed that the research was vital to the extension portion of the project.

NC State Personnel discuss management of soilborne pests with local growers at an on-farm-research trial in the Piedmont of NC

NC State Personnel discuss management of soilborne pests with local growers at an on-farm-research trial in the Piedmont of NC

“The experiments were complimented with extensive evaluation of the pathogen and microbial communities on roots,” explained Frank Louws, director of the NC State University Center for Integrated Pest Management and member of the working group. “These data advanced scientific understanding about the ecology, biology, dynamics and management of targeted plant pathogens and beneficial microbes.”

Plant breeders developed various breeds of resistant plants, increasing the likelihood of the crop’s success. Soil scientists found that mustard meal applied before planting helped strawberry yield but was less effective for tomatoes.

“Vigorous rootstocks using grafted tomatoes suppressed bacterial wilt, southern stem blight and root knot nematodes and increased yield similar to or better than fumigants in multiple field trials,   ” said Louws.

Once research results were in, specialists began training extension agents and consultants working with farmers. The specialists took extra care to inform growers of results and include them in trainings. Most strawberry growers in the Southeast are small to medium size, between 5 and 70 acres. Vegetable acreage is larger, from about 50 acres to over 1,500 acres, with some tomato growers managing over 6,000 acres.

According to Stephen Montzka, project leader of the Chlorofluorocarbons Alternative Monitoring Project at the National Oceanic and Atmospheric Administration (NOAA), atmospheric methyl bromide levels have declined substantially with decreased use of the fumigant, resulting in lower bromine levels in the atmosphere. Montzka reported the data during the 2017 Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions in San Diego November 12-15.

Dr Frank Louws discusses the process of grafting tomatoes, as one option to manage soilborne diseases with extension agents and growers at a Myrtle Beach Conference

Dr Frank Louws discusses the process of grafting tomatoes, as one option to manage soilborne diseases with extension agents and growers at a Myrtle Beach Conference (11-2016)

This decline accounts for one-third of the measured decrease in ozone depleting halogens above the Antarctica. The encouraging outcome is that the ozone hole above the Antarctic appears to be decreasing in severity, although this measurable change varies year-to-year depending on temperature and global volcanic activity, Montzka stated.

“A multifaceted extension and outreach program, in close cooperation with stakeholders, equipped most growers and agents with knowledge about the MBT program and was an instrumental component of the successful transition away from critical use nominations using methyl bromide,” said Louws.

“Much of the research and extension engaged stakeholders as key partners through on-farm-research trials,” he added. “Technical and economic barriers remain, and those will be best addressed through continued cooperation with growers, supporting industries, university programs and policy makers.”

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