Tri-Cal: Industry Research on Impermeable Films

Tri-Cal, a company in Hollister, California, has been experimenting with less permeable films for chemical fumigants for about a decade. For nearly 40 years, California farmers have depended on Tri-Cal to apply fumigants like methyl bromide, chloropicrin, and telone to soil where trees, vines, and tomato, strawberry and pepper crops are grown.

Dean Storkan, Tri-Cal's president, says that historically their research efforts have been aimed at decreasing the dosage of methyl bromide. "When we first began using these films about 10 years ago, we reduced the amount of methyl bromide needed for some uses by about 10 to 25 percent. As commercial films became even better, we got lower emission rates," he reports.

But, according to Storkan, part of the reduced emission rates came as a result of buffer zones instituted by the state of California's Department of Pesticide Regulation (DPR). (See "California Monitors Methyl Bromide Applications for 6 months,"Methyl Bromide Alternatives, Oct. 1997, pp. 5–6.) In 1993, DPR and California county agricultural commissioners set up parameters for buffer zones to better protect workers and others who may be exposed if methyl bromide escapes fumigation sites.

For its trials with the new impermeable films, Tri-Cal has the capability to measure methyl bromide concentrations under the tarp, but expects that California's DPR will monitor the applications on the periphery to ensure emissions are in line with mandated buffer zones.

"We, like Scott Yates of ARS, are now working with virtually impermeable films (VIF)," Storkan says. "These films are not yet commercially available, but we're testing their permeability and strength under true commercial crop production conditions. In fact, we have cooperative growers who are now trying these films. We hope the films will be commercially available in the fall of 1998."

In addition to permeability and strength, he says that Tri-Cal is also studying the glue used to hold VIFs together. "Growers now glue tarps together to cover fields. We're looking at how this glue works in sealing methyl bromide gas in the soil instead of allowing it to escape into the atmosphere. Durability of the plastic is also vitally important. Impermeability is what we're after, but if the sheet of plastic becomes full of holes, we've defeated our purpose in reducing emissions."

Storkan says that Tri-Cal is also looking at other chemicals as possible alternatives to methyl bromide. "We're investigating the use of chloropicrin, telone, basamid, metam sodium, and methyl bromide. And, we're experimenting with combinations of these chemicals," he reports. "We feel that through our own research and our cooperative research with scientists from federal and state governments and universities, we may find a viable alternative for methyl bromide for some uses on some crops. But, some of the potential alternatives will create new environmental issues."

Tri-Cal is also working cooperatively with Plastopil Hazorea, a company in Israel, on a project to produce a new soil fumigant package that will improve environmental quality as well as help U.S. and Israeli farmers.

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Last Updated: April 22, 1998