What If . . . ? The Strawberry Industry Without MeBr

Methyl bromide has been the cornerstone of many growers' pest management practices. But in January 2001, the amount of the soil fumigant available to them will be 50 percent of 1991 production levels—a decrease that could reduce yields.

Taken a step further, what if methyl bromide were suddenly unavailable? This scenario was presented recently to a select group of extension agents, growers, and researchers in the strawberry industry. A synopsis of their responses follows.

Two themes emerged: the efficacy of other chemicals compared with methyl bromide, and the lack of EPA registration for alternatives.

Soil Fumigation Alternatives

Soil fumigation accounts for 80 percent of methyl bromide usage. The main alternatives are combinations of chemicals: primarily Telone mixed with chloropicrin, Vapam with chloropicrin, or metam sodium with chloropicrin. Telone is most likely the front-runner, but it has drawbacks.

"In Florida, Telone is the most effective soil treatment, but farmers are squeezed by regulated buffer zones," explains Joseph Noling, an extension nematologist with the University of Florida's Institute of Food and Agricultural Services at Lake Alfred. In order to apply Telone in Florida, 300-foot buffer zones are required on agricultural lands abutted by occupied structures.

So, on a 22-acre rectangular farm surrounded by occupied structures, the farmer could grow only on the center 8 acres, according to Noling, adding pressure to an already tense situation.

Growers are keenly aware of the status of methyl bromide alternatives. "Right now, it looks like Telone/chloropicrin with an herbicide is the best alternative, but still not a very good one," says Marvin Brown, a strawberry grower in Florida. "And, unfortunately, many growers have no experience with Telone."

According to Florida extension agent Charles Hinton, "Cultural practices, such as cover crops and solarization, work only under ideal conditions. One hurricane can undo all the preparation work done during the summer."

In California, Vapam, Telone, and chloropicrin are the weapons of choice. But, Telone, a very good nematicide, can be used there only on an extremely limited basis due to regulatory restrictions. Caps limit Telone use in a township to 5,000 to 9,000 gallons per year and require 300-foot buffer zones. Once the cap is reached, no more Telone can be applied within the township borders, which means the chemical is not available to the remaining growers there. Vapam, identified as a carcinogen by California, is on the state's Proposition 65 list. (Proposition 65, also called the Safe Drinking Water and Toxic Enforcement Act of 1986, was a voter initiative passed to address citizen concerns about carcinogens and teratogens. The law prohibits businesses from discharging these chemicals into sources of drinking water and requires that warnings be given to individuals exposed to them.) Growers must have buffer zones and notify nearby landowners before they apply Vapam. Steve Fennimore, extension vegetable weed control specialist, University of California, Davis, says, "growers can administer chloropicrin followed by Vapam in drip lines in order to provide weed and disease control."

Another demerit for Telone is explained by Tommy Brock, a strawberry grower, of Plant City, Florida. "I've been treating with Telone for 3 years and find it has no residual effects, while methyl bromide leaves some residual effects for 3 to 5 years," he says.

In California, several materials are considered as possible alternatives, but they are not registered for pesticide use by EPA. These include Basamid, Vorlex (methylisothiocyanate plus 1,3—D), propargyl bromide, and methyl iodide. According to Frank Westerlund of the California Strawberry Commission, two materials stand out: "Efficacy studies to date show propargyl bromide and methyl iodide have the required spectrum of activity, and registration is needed as soon as possible."

Before it registers new active ingredients California requires EPA registration and specific toxicological tests. EPA takes several years to register a new chemical, provided toxicological and environmental data are acceptable; any tests California might require add additional time.

Herbicide Alternatives

Very few herbicide alternatives to methyl bromide are available for strawberries in Florida. Growers primarily spray Roundup between rows, since Devrinol doesn't seem to be very effective, according to Hinton. Some growers apply paraquat between rows to control weeds, while others use Vapam in drip irrigation. But these treatments add a step to field preparation and sometimes require new equipment.

Herbicides can also be added to Telone. "You can add an herbicide to Telone to get some weed control, although it is not as good as methyl bromide," contends Brock, who double-crops his strawberries with cherry tomatoes. This less effective weed control adds to his costs because workers must pull emerging weeds.

In California, Devrinol is the only material registered for application on strawberries. According to Westerlund, phytotoxicity problems and yield loss limit use of this chemical. Some farmers successfully use Devrinol for weed control in furrows but not in the crop. Other herbicides are either under evaluation or were eliminated as alternatives because of toxicology issues.

Fungicide Alternatives

Chloropicrin is relied on as a soil fungicide in both California and Florida. If this all-purpose fungicide fails to do the job, growers apply a species-specific fungicide. No other fungicides are on the horizon for future registration.

Economic Impact

Potentially, the strawberry industry could sustain the largest economic hit from the loss of methyl bromide. The industry will feel significant impacts in California and Florida, according to an economic model developed by John VanSickle, Charlene Brewster, and Thomas H. Spreen of the Cooperative Extension Service at the University of Florida, Gainesville.

Application of the model to Florida assumed use of a combination of Telone C17 (Telone with 17 percent chloropicrin) and Devrinol as a replacement for methyl bromide. This alternative anticipated a $71-per-acre decrease from preharvest costs and a 15-percent decrease in yields. This translates into preharvest costs increasing from $3.75 to $4.37 per flat. The low end of the economic impact estimated a 10-percent reduction in yields and the high impact, a 20-percent reduction in yields.

In the California scenario, the model used chloropicrin as the methyl bromide replacement, along with hand weeding. The expected impact of this alternative would be a $654-per-acre increase in preharvest costs and a 20-percent decline in yields, meaning per-unit preharvest costs would increase from $3.59 to $4.73. The lowest estimate is a 10-percent reduction in yields and the highest is a 30-percent reduction in yields. VanSickle theorizes, "The use of labor instead of chemicals for weeding equals higher production costs, which would deem California growers noncompetitive."

The model predicts that strawberry production in California would be particularly at risk, given the current state of knowledge about methyl bromide alternatives. Developing better alternatives is of paramount concern to strawberry growers. "We're relying on the university system and researchers to come up with a viable option," concedes strawberry grower Marvin Brown.

Last Updated: July 24, 2000