New groundwater protection rules affecting herbicide choices in almonds

As almond growers made plans for herbicide programs this fall, many had an additional issue to face. On top of air quality standards and food safety, growers now have California's new Ground Water Protection Program to contend with.

Ground Water Protection Areas (GWPA) have replaced Pest Management Zones. With that change are new rules requiring growers to obtain special permits for herbicide use in GWPAs. While the old PMZs covered 313,000 acres statewide, the new GWPAs include “about 2.4 million acres across the state where groundwater is most vulnerable to pesticide contamination from leaching and runoff,” according to a California Department of Pesticide Regulation bulletin.

GWPAs are divided into two categories: runoff and leaching. Fields in either category cannot be treated with any of the state-designated 6800(a) list of herbicides (atrazine simazine, bromacil, diuron, prometon, bentazon and norflurazon) without going through a permit process with the county agricultural commissioner. The permit requires growers to agree to implement a management practice designated by CDPR to prevent additional groundwater contamination.

Growers choose from a list of management practices for either runoff or leaching GWPAs.

“If growers are operating in a GWPA, then the regulations require them to use mitigation practices — either runoff or leaching, depending on the GWPA — or to adopt alternatives, which could be other chemicals or other cultural practices,” said Glenn Brank, a CDPR spokesperson.

Difficult regulation

According to Kurt Hembree, University of California Cooperative Extension weed control farm adviser for Fresno County, this new regulation will be particularly difficult for certain tree, vine, and citrus growers. “The management practices required for using the herbicides on the list are not clearly defined, they are ‘one size fits all’ where they should be more clearly defined by crop. It is not practical for growers in certain situations to use some of these practices,” he said. For example, he points out, citrus growers cannot use physical incorporation, one of the mitigating practices, because citrus trees have shallow roots and may be damaged.

“The three main herbicides used on pistachios are Devrinol, Goal, and Surflan, and for nonbearing, Prowl, so the GWPA may not affect them as much,” Hembree said. “Of these herbicides, Surflan is a strong candidate for almond growers. For nonbearing trees, they can use Prowl or Treflan with a burndown herbicide, and for bearing, growers can use a tankmix of Surflan with Goal and a burndown. By using fairly high rates — 5-8 pints of Goal and 1 gallon of Surflan in late winter — growers can get long residual control that will get them through the season with only one or two additional burndown sprays.”

Surflan A.S., formerly a Dow AgroSciences product, is now sold by United Phosphorus Inc.

Grower's decision

With 40 percent of his almonds in a GWPA, grower Garrett Bowman, Salida, Calif., made the decision to stay with non-6800(a) herbicides rather than implement a management practice under the new rules. Bowman, who graduated from UC-Davis in 1999 with a major in Agricultural Systems and Environment, and his father Art Bowman, farm 450 acres of Nonpareils with Aldrich and Carmel as pollinators. Nonbearing replants account for 170 of their almond acres.

The Bowmans had been using Prowl applied in the fall and early winter on nonbearing trees, but Garrett reported they are using more Surflan because it is more effective.

“Surflan does a better job than Prowl,” he reported. “As the operation grows, I want to make one trip instead of two. I can get Surflan to hold on longer than Prowl.”

Bowman puts Surflan out with Roundup in the fall or early winter on nonbearing trees, unless the weeds are too high, in which case he uses the burndown first, then comes back with Surflan. “I like Surflan because of the tree safety,” Bowman said. “I will use it for the first three years of tree growth.”

Bowman treats nonbearing trees on the strips only, and plants rye or beans for a cover crop in the middles.

“Our No. 1 issue right now is GWPA, and No. 2 is air quality,” Bowman said. “At harvest, we try to keep a bare, flat floor to mitigate dust and we'll also have to get new harvest machinery to comply with PM10 requirements.” To keep weeds down, Roundup is sprayed before harvest, around mid-July, and grass in the middles is mowed. This program lasts through Nonpareil harvest.

“Before we shake the pollinators, we will come back with Gramoxone, sometimes making two applications,” he said.

To meet air quality standards, the Bowmans are also chipping and spreading prunings instead of burning. “With the microsprinklers, chips break down well by harvest and are not a problem,” Garrett said.

New grower

Grower Jerry Goubert, who farms 1,700 acres of tomatoes, alfalfa, walnuts, spinach and beans in the Patterson area, planted his first almond orchard in February 2004. Looking for a way to diversify into a profitable permanent crop, he put in 90 acres of Aldrich, Fritz, Nonpareils, Buttes and Padres, and will plant an additional 68 acres this January.

After planting the trees, Goubert treated twice with Gramoxone, followed by Prowl. “This holds until the fall, when I use Roundup,” he said. “When trees start to bear, I'll switch to Surflan, applying in a tank mix with Roundup and Goal. This program will not be a problem in my GWPA field and two applications will give me a full year of control. At harvest, I may have to come back with Roundup, then apply Surflan one month before shaking to have a clean surface,” he said.

From Brank, comes this reminder about the new GWPA program:

“Groundwater regulations are like any other pesticide regulations — they are the law, and pesticide users bear responsibility for compliance, and we expect full compliance. DPR and the ag commissioners are always ready to work with growers who make good-faith efforts to obey the law.” He adds that county ag commissioners, with their knowledge of local conditions, can help growers apply the regulations correctly.

“For about 20 years, groundwater contamination was a continuing problem,” Brank said. “DPR's regulations offer a pro-active approach to prevent groundwater contamination while providing growers with reasonable options for effective pest management. By avoiding contamination before it occurs, we can give growers more flexibility and meet our legal responsibility to protect the environment.”

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