Methyl bromide alternatives must be found

With the phase-out of methyl bromide in sight, it’s time to start trying alternatives to the fumigant, say University of Georgia researchers.

Last year, University of Georgia Extension Weed Scientist Stanley Culpepper and University of Georgia Extension Plant Pathologist David Langston looked at six fumigant, two herbicide and two plastic mulch options on spring and fall crops of eggplant and pepper.

“Growers need to be trying something new for 2005,” Culpepper says.

Based on 2004 results, Culpepper and Langston found that a herbicide system and eventual adoption of virtually impermeable film (VIF) will likely be needed in fields with moderate to severe nutsedge infestations. VIF, however, is twice the cost of low-density polyethylene film.

“The work with VIF is exciting,” Culpepper says, “but there are great concerns dealing with the time interval necessary between applying fumigants under VIF and transplanting. The fumigant lasts much longer than what growers are used to with the commonly used LDPE. The potential for herbicide injury is greater with VIF than LDPE film. In addition, the plant-back interval could be three to four times longer with VIF than LDPE compared to methyl bromide under the low-density material.

“We found several effective methyl bromide alternatives to control nutsedge,” Culpepper said at the recent Southeast Regional Vegetable Conference held in Savannah, Ga. Culpepper suggests trying the alternatives on a small scale.

The researchers compared methyl bromide with Telone II followed by chloropicrin; Telone C35 followed by chloropicrin; Telone II followed by K-Pam; methyl iodide or MIDAS; and MIDAS followed by chloropicrin

In the spring trial, the researchers found success with only one of the six alternatives to methyl bromide: Telone II followed by K-Pam. Control with this option was more than 90 percent 62 days after fumigation. All of the spring treatments were without a herbicide program.

In the spring trial, at 37 days after fumigating, all six fumigant options controlled at least 90 percent of the nutsedge.

“The spring application was extremely effective when we got the rate right.

“Nutsedge control in the fall is more difficult than in the spring and poses greater challenges,” Culpepper says. “So, it is advised to learn application procedures of alternatives in the spring crop.”

In the fall crop, methyl bromide had only 67 percent control of purple nutsedge under the LDPE film without the herbicide program.

The researchers saw a trend toward control of nutsedge populations when Telone C35 and MIDAS were used with a herbicide program. Dual, Command and Devrinol were used in the trials. Dual and Command are only labeled for use in pepper and will cause severe injury to eggplant.

In the fall crop, the researchers used Telone C35 under VIF followed by chloropicrin with and without a herbicide program; MIDAS (98:2) under LDPE and VIF with and without a herbicide program; MIDAS (98:2) under LDPE film with a herbicide program; MIDAS (50:50) under VIF with and without a herbicide program; and methyl bromide under LDPE film with a herbicide program and under VIF with and without a herbicide program.

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