Cilantro and dill growers gain an additional weed control tool

Cilantro and dill growers and researchers work together to expand registration of clomazone through IR-4 Project.

Author – David Kuack

Commercial growers of cilantro (shown) and dill worked with researchers to conduct efficacy trials with clomazone herbicide in efforts to expand its label registration through the IR-4 Project. Photos by Brandon Narron, Ratto Bros.

Growing multiple vegetable crops can be a blessing and a curse. Ratto Bros. Inc. in Modesto, Calif., produces 38 different crops, primarily leafy greens and herbs.

“We grow a broad spectrum of crops,” said Brandon Narron, ranch manager at Ratto Bros. “Our biggest crop acre-wise is cilantro. Other crops include different types of lettuce, kale, Swiss chard, basil, dill, fennel, bok choy and parsley. We plant very small plantings. For us a big planting is 5 acres. But at any one time we will be operating 650 small fields in production.

“Most California growers don’t have nearly the variability in crops that we have on our farm. At times I wish we had more monoculture crops because of the weeds, insects and diseases we have to keep up with. Other growers will offer the items that we produce in their list of products, but it doesn’t necessarily mean they grow the crops themselves. They are working with contract growers to produce the crops they don’t.”

Ratto Bros. grows on 1,100 acres of its own land as well as leasing 80 acres. The company has also started contracting with other growers. Ratto Bros.’ produce is shipped throughout the United States and Canada.

“Our customers include Walmart, Kroger, Sophie’s Kitchen and Save Mart Supermarkets,” Narron said. “We service the produce markets in Los Angeles, Oakland and San Francisco. We also sell to processors that make up salad blends. Most of our product is sold fresh.”

Looking for a few good herbicides

Eighty percent of the crops produced by Ratto Bros. are direct seeded with the remaining 20 percent grown from transplants.
“Because of the variability in the crops we grow, we are looking for overall weed control,” Narron said. “If there is an herbicide and it’s effective on a weed that we don’t have on the farm, we are still interested in trialing it. We never know which weeds we’re going to have trouble with in the future so the more tools we can help develop the better off we are.

Ratto Bros., whose biggest crop is cilantro, assisted in conducting efficacy trials with clomazone at its farm in Modesto, Calif. Photos by Brandon Narron, Ratto Bros.

“We are using whatever herbicides are registered in California. I used to spend hours searching data bases to find the herbicides that were registered so that I could trial them. As far as our herbicide rotation, it follows our crop rotation. We don’t have corn and soybeans following corn and soybeans. We have 38 different crops. We are not going to be using the same herbicides year after year. As we rotate crops we also rotate herbicides. Crop rotation has helped with preventing herbicide resistance. Currently we’re fallowing about 75 acres of land, which is unheard of for us. That is why we are having contract growers producing some crops for us.”

Narron, who has been with Ratto Bros. for six years, said the company has to deal with a wide spectrum of weeds.

“We are extremely tight on land and it can be tough to grow,” he said. “We get a lot of purslane, nut sedge, malva, shepherd’s purse, annual bluegrass and chickweed. One of my directives when I came to work here was when IR-4 Project or the University of California wants to put in a trial that I should assist them any way I can. In the long run we will benefit from the trials.

“Ray Ratto is a strong believer in IR-4. He decided that IR-4 was the way to go to try to get some products registered for the minor crops that we produce. I have boxes of studies that Ray and other people who were employed by the company did with IR-4 on the farm.”

Expanding the label for clomazone

Cilantro is Ratto Bros. biggest crop. It usually produces two crops annually on 200 acres. When IR-4 approached Ratto Bros. about conducting trials with clomazone herbicide on cilantro, Narron said the company provided the fields for both efficacy and residue studies.

“Even though clomazone isn’t currently labeled for use in California we were interested in looking at its effectiveness,” Barron said. “I am very concerned about herbicide resistance. Someday clomazone may receive registration for use here and we’ll be able to use it. The weeds that we have to control won’t be resistant to it because we haven’t used it. Then we will have a product that will last for some time.”

Bernard Zandstra, horticulture professor and weed scientist at Michigan State University, conducted efficacy and residue trials with clomazone on cilantro and dill with growers in his state.

“I have conducted field trials for weed control efficacy and crop safety of this pre-emergent herbicide for over 10 years on several crops, including cilantro and dill,” Zandstra said. “I found clomazone helps control several weeds. Field sandbur and large crabgrass are two serious weedy grasses that clomazone suppresses quite well. It also suppresses some serious broadleaf weeds, including common lambsquarters, common groundsel, common purslane, common ragweed and velvetleaf.

Because cilantro and dill (shown) have short production cycles, it is important that commercial growers have access to pre-emergent herbicides like clomazone. Photos by Brandon Narron, Ratto Bros.

“If clomazone is used together in a tank mix with other herbicides that are commonly applied, such as Lorox (Linuron) or Caporol (Prometryn), which are mainly broadleaf herbicides, it really does a great job of controlling nearly all of the weeds. Growers are never going to get 100 percent control, but they can achieve 90+ percent control for annual weeds.”

Zandstra said cilantro and dill are minor crops in Michigan with less than 20 growers producing a half acre or less of the crops.

“Visiting with cilantro and dill growers I could see the weed control problems they were having,” he said. “With so many of these minor crops there have been very few herbicides labeled. Essentially I have spent my career finding uses for these herbicides and then working with IR-4 to achieve the registrations and labels. Cilantro and dill are good examples of very minor crops.”

Zandstra initially did trials with clomazone on cilantro and dill at the university’s research farm.

“Once we find herbicides that looked like they would work with a crop then we reach out to commercial growers to conduct efficacy/safety trials with them,” he said. “It is easy to work with these growers because they have the crops growing in their fields. It is a lot easier to conduct the trials because we only have to make test plot applications. The growers take care of the crops during the season. It’s important that the growers participate in the trials and it doesn’t take a lot of effort on their part.”

Planting of cilantro and dill in narrow rows makes weed cultivation difficult. Photos by Brandon Narron, Ratto Bros.

Zandstra said because cilantro and dill are 45-60 day crops, it is important to have a pre-emergent herbicide like clomazone.

“Cilantro and dill are normally planted in narrow rows, so cultivation is difficult,” he said. “Both of these crops grow rapidly, so a good, effective pre-emergence treatment should provide sufficient weed control until close to harvest.

“Most cilantro and dill growers are small operations and these crops are rotated to different fields each year. Herbicide resistance really isn’t an issue because these crops are not going back into the same fields and the same herbicides are not being used year after year.”

For more: Brandon Narron, Ratto Bros. Inc.,;

Bernard Zandstra, Michigan State University, Department of Horticulture,

PR# 11092 Cilantro (Annual weeds)

PR# 11091 Dill (Annual weeds)

David Kuack is a freelance technical writer in Fort Worth, Texas;