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Methyl bromide replacement iodomethane moves toward registration

It will likely be later than that before the California Department of Pesticide Regulation makes a decision on whether to allow producers in California to use the compound.

Both of those time lines are later than Arvesta Corp. hoped for in getting its Midas brand of iodomethane on the market.

While going through the state and regulatory mazes, Arvesta is conducting extensive field trials to refine application technology to learn how best to apply the product on a wide array of crops as well as to mitigate its high cost. It is expected to be cost 20-50 percent more than methyl bromide.

That is a major issue for strawberry growers like Pedro Casailles of Salinas, Calif., who now spends $1,300 per acre to fumigate with methyl bromide before planting his strawberry crop. Arvesta conducted trials on Casailles farm.

Farmers expect to lose methyl bromide within two years as a long-effective tool to control diseases and weeds because if its ozone depleting properties. However, EPA is currently accepting applications for exemptions from the phase-out rules for methyl bromide. In situations in which the loss of methyl bromide would create undue hardships (large-scale commodity market disruptions, lack of suitable alternatives) critical use exemptions (CUE's) may be granted. The exemption is for a period of three years, 2005-2007. If granted, the exemption amounts to a three-year extension of the Jan. 1, 2005 deadline when methyl bromide must be phased out in the United States.

Alternatives search

An army of private and public scientists have been scrambling to find methyl bromide alternatives or replacements. A myriad of tactics have been investigated to find something or a combination of techniques that will control the same pathogens and weeds that methyl bromide has for decades. This involves a wide array of chemicals applied in a variety of ways over many soil types and crops using a rainbow of bed mulches.

It is a daunting task, and time is running out. As one group of researchers looking at methyl bromide alternatives in strawberries said, "We need time — there is very little time to redo decades of work before methyl bromide is no longer available."

While alternatives have been identified, no silver bullets have been found as yet. However, methyl iodide may come as close to it as any so far, according to Michael Allan, Arvesta product manager for fumigants.

He calls the Arvesta product Midas a "replacement" product rather than an "alternative" because it has proven to be at least as effective as methyl bromide. "Unlike some alternatives, Midas can control both diseases and weeds," he said.

Researchers at the University of California, Riverside discovered methyl iodide was as effective as methyl bromide and safer for the ozone layer. UCR researchers found that methyl iodide remains in the atmosphere for four to eight days while methyl bromide may remain for two years.

Same kill spectrum

Methyl bromide has the same spectrum of kill as methyl bromide, according to researchers. In addition, the UCR scientists found that liquid methyl iodide is safer for workers to apply than methyl bromide, a gas when it hits the air.

Arvesta has bought licensing rights from UCR and is ferrying its product Midas through the registration process.

Hylon Kaufman, marketing communications manager for Arvesta, said the company had hoped federal registration would be awarded by last September, but that did not prove possible.

However, the submission of the registration packet did not "expose any issues with the registration process and data package. Everything remains on track and is processing quite well with EPA," she said.

EPA and DPR are sharing evaluation responsibilities for the compound, but California requires more data for registration than EPA. Specifically, this involves long-term chronic health toxicity studies.

According to Arvesta, DPR could issue conditional registrations of iodomethane products provided that DPR is given interim reports that ongoing long-term studies and that these studies support registration of the products.

"Arvesta is actively and diligently fulfilling these studies. We hope this will streamline and thus expedite the review of the Midas registration package," said Kaufman.

More effective

Hussein Ajwa, associate specialist, vegetable crops, University of California Cooperative Extension, has tested iodomethane for use on strawberries for three years and says "pound for pound is it more effective than methyl bromide

"It is a true fumigant" that moves through the soil at 10 times higher pressure than methyl bromide. Iodomethane would be used much like methyl bromide to propel chloropicrin, another fumigant, through the soil to control diseases.

"I think strawberry growers can get by with much less methyl iodide than with methyl bromide," he added, suggesting the rate for methyl iodide could be 150 pounds per acre vs. 250 to 270 pounds for methyl bromide. Almost half of the methyl bromide now used in California is applied to strawberry acreage.

Along with the search for chemical alternatives have been efforts to change application techniques, focusing on applying fumigants via drip systems rather than injecting and tarping. This not only reduces the amount of chemical needed, but also reduces emissions, said Ajwa.

Most of the strawberries in the state are now irrigated with drip irrigation and the percentage fumigated using the drip irrigation system is growing.

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