Source:  Roy Roberson, SOUTHEAST FARM PRESS, 2/5/10

Southeast fruit and vegetable growers have a number of alternatives to methyl bromide, which is being rapidly phased out. Finding the right alternative is critical to the future success production in the region.

Methyl bromide use has steadily declined since it was identified as an ozone depleting chemical back in the 1990s. In the past few years fruit and vegetable growers in particular have struggled to find suitable replacements for the highly effective soil sterilant.

Methyl bromide in soil fumigation combats a host of devastating organisms and diseases. These include nematodes, soilborne fungi, phytophtora, weeds and diseases which attack roots and thus, destroy and kill the plants.

While methyl bromide wasn’t 100 percent perfect, it proved to be a highly flexible, highly effective and cost effective method of weed and disease control in fruit and vegetables. It was used extensively in fruit and vegetable production from Florida to Virginia for a wide range of disease and weed problems.

Frank Louws, a plant pathologist and fruit and vegetable researcher at North Carolina State University says the loss of methyl bromide presents some disease management challenges for fruit and vegetable growers in the Southeast.

By 2015 methyl bromide use is expected to be eliminated worldwide. The decrease in agricultural use of methyl bromide has already slowed the rate of ozone degradation, By 2040, the ozone layer is expected be fully regenerated, hence farmers aren’t giving it up for nothing, Louws explains.

Rob Welker, heads a regional methyl bromide replacement program headquartered at North Carolina State University. He works with Louws and other researchers at North Carolina State, Clemson and Virginia Tech universities to find cost effective, effective replacement products and production systems to replace methyl bromide.

Speaking at the recent North Carolina-South Carolina Fruit and Vegetable Growers Association Annual Meeting, Welker said, “Growers are not likely to have a single product to replace methyl bromide, but there are a number of systems that will work in specific crops and specific cropping conditions.”

For Southeast fruit producers, Welker says on-farm tests in the Carolinas and Virginia have been highly successful using Telone C-35, PiClor 60, Midas, Inline and Paladin. All but Paladin are registered for use on fruit. Paladin has been used under an experimental use label for several years in the Southeast and is expected to get a full label for 2010.

Telone C-35 soil fungicide and nematicide controls all major species of nematodes, including root knot, lesion, stubby root, dagger, ring, pin and cyst nematodes.

The addition of chloropicrin allows Telone C-35 to have significant activity on soil diseases, such as fusarium, verticillium, pink root, phytophthora and pythium.

Telone C-35 is injected into the soil as a liquid and immediately converts to a gas, creating a zone of protection around developing roots. As a fumigant, Telone moves throughout the soil profile on its own, rather than requiring water or incorporation for movement.

PiClor 60 is one of many products containing picloram and is widely used in tree fruit production. Picloram is in the pyridine family of compounds and is a systemic herbicide used for general woody plant control.

Midas is a broad-spectrum soil fumigant that effectively controls a broad range of soil-borne diseases, nematodes, weed seeds and insects that threaten high-value crops, like fruit and vegetables in the Southeast.

Since it was introduced to the U.S. market, Midas has come under consistent attacks by environmental and labor groups because of its toxic affect on workers. The active ingredient, methyl iodide, has been linked to a number of human health problems, especially among migrant farm workers in California.

Though unquestionably a suitable methyl bromide alternative in many fruit and vegetable crop production systems, the big question is safety.

InLine is a soil fungicide and nematicide. It is a multi-purpose liquid fumigant for the preplant treatment of soil to control nematodes and symphylans, and to manage certain soilborne diseases in cropland using drip irrigation systems only.

Though highly effective in systems equipped for legal application, InLine use is restricted. Welker emphasizes that all these materials have a place as methyl bromide alternatives, but none so far have the total package for crop protection as did methyl bromide.

“All of these alternatives have issues. In general they are not as forgiving as methyl bromide, environmental conditions have to be optimum for optimum results and these materials don’t move throughout the soil as freely as did methyl bromide,” Welker says.

Paladin contains the active ingredients dimethyl disulfide plus chloropicrin. In extensive testing in Georgia, UGA Researcher Stanley Culpepper says, “Paladin has proven to be effective in managing many pests and has the potential to be adopted depending on the price structure and our ability to manage its odor.”

“We test these materials in on-farm situations that are as close to how they would be used in a commercial operation as possible. Using these materials alone or in combination with each other, we have had good results,” Welker says.

“In addition to mixing and matching products to a particular farming operation, we have applied these materials under different plastic mulches, both shank-applied and drip-applied. How well one works versus the other really depends on the farm and how these materials are applied,” he adds.

None of these alternatives to methyl bromide work well under wet, cool conditions. Wet conditions, especially creates problems to control. Vegetable producers in the mountains of western North Carolina have had some failures with these methyl bromide alternatives.

Welker urges growers to attend regional strawberry and vegetable field days that highlight his multi-state methyl bromide alternative program. Growers can see these materials in different combinations and different application methods, the North Carolina State researcher says.