Grower Reports on Field Tests for Preplant Methyl Bromide Alternatives

For a year, Dave Murray, a strawberry grower in Oxnard, California, has participated in the field validation project initiated by the Agricultural Research Service in 1995. The mission of the project—which is also sponsored by the California Strawberry Commission and the University of California—is to validate in the field, on as large a scale as possible, preplant alternatives to methyl bromide fumigation. (See Methyl Bromide Alternatives, April 1996, pp. 1–2, "Update on Field Tests for Preplant Methyl Bromide Alternatives.")

Murray, who grows Camerosa strawberries, fumigates with methyl bromide to increase plant vigor and control weeds. "Without methyl bromide, my crop would be subjected to increased risk from soilborne and root diseases."

"I used four treatments for my experiments: methyl bromide, Basamid, Telone II with chloropicrin, and chloropicrin by itself," Murray says. "I must say that Basamid, by far, outperformed the other alternatives."

Murray used half-acre plots for each experiment. In the control plot, he fumigated with methyl bromide and chloropicrin (57:43) at 325 pounds per acre. Yield was 7,920 pounds per acre.

He applied Basamid to two replicated plots: one with 350 pounds per acre; the other, 450. "At the beginning of March, yields from both of these plots were significantly higher than those from the methyl bromide plots," he reports. "I'm still collecting data, but yields through March 6 are the most important since that is when the market price is highest."

Plots fumigated with 400 pounds per acre of Telone II/chloropicrin (65:35) yielded about the same as the methyl bromide plots. "But I started to see a change after March. Production in this plot started to drop off somewhat," Murray says.

The plot treated with only chloropicrin (at 200 pounds per acre) produced slightly higher yields than the control.

According to Murray, controlling weeds is just as important as increasing or maintaining yield. "Methyl bromide was the only treatment that completely controlled weeds. But Basamid did a fairly good job. It controlled weeds at an acceptable level, whereas Telone/chloropicrin didn't do well at all."

"As a production manager, I need to know about every viable alternative to methyl bromide. We are going to lose methyl bromide after January 1, 2001. I appreciate being included in this study because, to stay in business, growers must have alternatives and I want to know as much as I can about all the possible options."

At this time, Murray says, Basamid seems to be the choice alternative chemical. Although Basamid is not yet registered for use on food crops, the chemical company BASF is actively seeking registration from the U.S. Environmental Protection Agency.

"One problem I have with Basamid is that you really need ideal conditions for it to work effectively," Murray notes. "Ideally, soil temperature needs to be 70 degrees or greater. In granular form, Basamid must react with soil moisture to degrade to a gas. We fumigate in September and plant in October. Is this enough time to convert Basamid from granular to gas form and have the gas dissipate?"

He says that in tests this year, the soil was free of gas in 2 to 3 weeks after treatment.

To test soil readiness in this study, Murray planted a pepper plant. The plant survived, which meant that the soil was free of gas. Had the plant died or growth been stunted, more time would have been needed to clear the soil of the gas.

Basamid is currently registered by EPA for nonfood uses such as in horticultural nurseries, forest tree nurseries, turf grass production, and golf course green construction and renovation. It can also be used on nut and nonbearing fruit crops. EPA granted an experimental use permit for growers in the validation program to use the chemical for field tests.

"The bottom line is: Strawberry growers need an alternative. This project has shown that Basamid will work if conditions are favorable," Murray says.

According to Ken Vick, USDA methyl bromide coordinator, some alternatives may or may not work equally well under fluctuating conditions, and their limitations must be explored.

"Methyl bromide is a compound that takes care of variabilities in temperature, rainfall, soil moisture content, and pest pressure. And after decades of use, it continues to be a robust fumigant that works over a wide range of conditions," he says. "We've been testing methyl bromide alternatives at different locations over a period of years to determine the extent to which they can handle variabilities of these factors. We intend to continue our research on Basamid as well as on other alternatives to compare their effectiveness with methyl bromide under fluctuating conditions."

Last Updated: July 24, 1998