Growing Strawberries Without Fumigants

UC Explores Alternatives to Fumigants for Strawberries

By Pam Kan-Rice, UCANR Assistant Director, News and Information Outreach

Strawberries, which generated $2.2 billion for California growers mainly on the coast in 2019, are sensitive to soilborne diseases. Strawberry plant roots infected by fungi are unable to take in nutrients and water, causing the leaves and stems to wilt. The diseases reduce fruit yields and eventually kill infected plants.

To protect the delicate plants from pathogens, strawberry growers fumigate the soil with pesticides such as chloropicrin and 1,3-dichloropropene before planting transplants. Due to the potential negative effects on the environment and human health, however, use of fumigants are highly regulated and developing non-fumigant alternatives has been a priority of the strawberry industry.

For a biological alternative to manage soilborne diseases in strawberries, Joji Muramoto, UC Cooperative Extension organic production specialist based at UC Santa Cruz, has received a $411,395 grant from USDA National Institute of Food and Agriculture to study the ability of other crops to suppress strawberry pathogens in the soil.

Verticillium wilt, caused by Verticillium dahliae, is a common soilborne disease that can be controlled with anaerobic soil disinfestation (ASD), a fermentation-based biological treatment using carbon sources such as rice bran under plastic mulch in moist soils for 3 to 5 weeks in autumn. About 2,000 acres of berry fields, mostly organic, were treated with ASD in California and Baja California, Mexico, in 2019.

In 2008-09, the diseases fusarium wilt, caused by Fusarium oxysporum f. sp. fragariae, and charcoal rot, caused by Macrophomina phaseolina, emerged in Southern California and now threaten strawberry plants throughout the state.

ASD isn’t as effective against F. oxysporum and M. phaseolina unless it is applied in summer on the coast. As saprophytes, they feed not only on living plants, but also can colonize crop residues and rice bran especially at lower coastal temperatures in autumn. Treating fields on California’s coast with ASD during summer is difficult because it competes with the vegetable production period.

Based on promising studies in Asia and other areas, Muramoto plans to test alliums – such as onion, bunch onion and leek – and a certain variety of wheat (Summit 515) to see if they will suppress F. oxysporum and M. phaseolina. His team will conduct a series of greenhouse and field trials and test these crops with and without ASD to compare the effects on soilborne pathogens.

“Studies have shown the potential of using allium crops to control Fusarium wilt, and Summit 515 wheat for charcoal rot,” Muramoto said. “Our goal is to examine the effectiveness of suppressive crops, optimize them for California strawberry production systems, and evaluate their economic feasibility for commercial use.”

“No single tactic is likely to replace fumigants,” he said. “Integration of multiple biological approaches such as crop rotation, ASD, and use of resistant strawberry varieties is a key to develop a successful non-fumigant-based soilborne disease management strategy for strawberries. This project is a part of such broader efforts.”

At the end of the three-year study, he plans to share the results at workshops, field days and webinars.

Rachael Goodhue, UC Davis professor of agricultural economics; Carol Shennan, UC Santa Cruz professor of environmental studies; and Peter Henry, USDA Agricultural Research Service plant pathologist, are collaborating on the study with Muramoto.

UC Agriculture and Natural Resources brings the power of UC to all 58 California counties. Through research and Cooperative Extension in agriculture, natural resources, nutrition, economic and youth development, our mission is to improve the lives of all Californians. Learn more at ucanr.edu.

California Ag Today2020-09-30T11:10:49-07:00September 30th, 2020|

Food Safety on Strawberries

Enhanced Safety Practices on California Strawberry Farms

By Tim Hammerich, with the AgInformation Network of the West

Strawberries are grown year round in the state, so when COVID-19 hit, harvest was in full swing in Southern California. Luckily the industry has developed a strong food safety training program over the past 15 years including print and video materials as well as in-person training.

This allowed them to respond quickly, says California Strawberry Commission Communications Director Carolyn O’Donnell.

“So starting with that baseline of food safety, we were able to build off of two specific pillars that are in that food safety program. And that includes coming to work when you’re well and not coming to work when you’re sick. And the other one is about adequate hand-washing,” said O’Donnell

The commission has leveraged the strong established food safety training program to get the word out about emphasizing these pillars. O’Donnell says they have also been communicating directly with employees.

“We’ve been running on public service announcements on Spanish language radio throughout the central coast of California where strawberries are being grown,” O’Donnell said. “And then we’ve been also doing a Saturday morning hosted program for about an hour on our radio station that definitely caters to that farm worker audience. And we’ve brought in a health person every time to talk about the ways to stay healthy, not only on the ranch, but when you’re at home.”

The program, called the “I Pick Safety” program, allows employees to work safely, and consumer to know that their delicious California strawberries are safe to eat.

AgInfo.net is the largest Radio Network in the West with 140 Affiliate Radio Stations.

California Ag Today2020-05-27T22:10:32-07:00May 26th, 2020|

Even Organic Production of Strawberries Not Sustainable

Data Shows Even Organic Production Uses Resources

By Jessica Theisman, Associate Editor

Is growing strawberries organically sustainable? That’s something that Surendra Dara is trying to find out. Dara is a UC Cooperative Extension Advisor in Entomology and Biologicals. He is based in San Luis Obispo County as well as Santa Barbara County. Dara met with California Ag Today recently and let us in on his research and some of his findings.

“I have not come across a mainstream grower that has told me that organic is sustainable,” Dara said.

After pulling in data and understanding the inputs, Dara is asking if there is anybody out there that has a different opinion.

“When we are talking about sustainability, we are looking only in terms of non-chemical being the sustainable, ecological practice,” he said.

There are such things as organic pesticides that harm natural enemies.

“Some of the organic ones can be as bad as some of the chemicals,” Dara said.

Data is showing that growing strawberries organically has not been sustainable economically. In terms of the carbon footprint and the bigger picture, “even organic production is not sustainable with the resources because certainly some resources are being used up,” Dara said.

California Ag Today2021-05-12T11:05:02-07:00July 10th, 2019|

2019 Strawberry Harvest is Brisk

Labor Tight, But Incentive Programs Keep Berries Harvested

By Patrick Cavanaugh, Editor

The 2019 strawberry harvest is going strong, and field employees are busy picking at the height the ripeness. Carolyn O’Donnell, a communication director for the California Strawberry Commission based in Watsonville, said lots of hands are harvesting the berries.

Carolyn O’Donnell, communications director, California Strawberry Commission

“We need to harvest the berries when ready,” O’Donnell said. “We can’t leave the ripe berries on the plant a few extra days, and we can’t harvest them early and then ripen them in some other modified atmosphere. They have to be picked when they’re ready to go. So, timing is part of it, as well as just having an adequate supply.”

O’Donnell explained how growers are handling the tight labor supply.

“It’s been a challenge. The growers have been doing all kinds of different incentive programs. Definitely, wages have been raised, different benefits have been offered, but we do find that growers are still struggling to keep up with their harvest,” O’Donnell said.

And when those harvesters out there picking the strawberries, they want to make the money, and they are in fact running back and forth with their trays to refill them.

“We are definitely in a busy harvest season right now. And so with a quick harvest comes incentive pay. And harvest workers will be hustling a little bit more. There are lots of berries to pick. There is money to be made,” O’Donnell said.

California Ag Today2019-07-08T16:37:07-07:00July 8th, 2019|

Bio-Control for Strawberry Growers

Strawberry Growers Lean on Biologicals to Manage Pest

By Jessica Theisman, Associate Editor

California Ag Today recently met with Surendra Dara, a UC Cooperative Extension entomologist based in San Luis Obispo County. According to Dara, California strawberry growers follow many sustainable options.

“Growers are well-educated and have a support system that provides information to them very regularly,” Dara said.

Growers try to apply as much of the IPMs as possible, but there is always a lot more scope in terms of using non-chemical alternatives. That is an area that has room to grow.

“The more we know about the options and their potential, they can be more adopted,” Dara said.

He explained that the strawberry growers often lean on biological insects such as beneficial mites that treat those damaging insects. It’s all part of IPM.

The insects are used outdoors along with in greenhouses.

“A bio-control is very well done in strawberries for mite control, but we do not have similar natural enemies for other pests,” Dara said.

There are botanical and microbial options for pest and disease management, and a lot of work is being done about understanding how they work and placing them in the right strategy.

“So, there is definitely plenty of options for us,” Dara said.

California Ag Today2021-05-12T11:01:47-07:00June 28th, 2019|

Electric Tractors Will Soon Be Available

With So Many Electric Cars, Why Not Electric Tractors?

By Patrick Cavanaugh, Editor

There are many different models of electric cars—they are even mainstream in most U.S. cities and other countries—and now farmers may soon have electric tractors to use in specialty crops in California.

Bakur Kvezereli is president and CEO of Ztractor, the first autonomous electric tractor for specialty crops. Kvezereli, who is based in Palo Alto, explained why the tractor is being developed in California.

“First, California is our market. Second, we teamed up with some great engineers, who graduated from Stanford, and my school, which was MIT. We were friends, and we wanted to look into this technology looking to replace the 25 or 30 HP diesel motor as well as the 30-gallon diesel,” he said.

“And we started as an electric tractor company in September 2017. And in two months, we realized that to achieve an electric tractor, you have to find a solution for making it autonomous,” Kvezereli explained.

“We now have three models in our manufacturing pipeline. One 24 horsepower will be available to the farmers this year. The next model will be a bigger tractor, 45 horsepower, which will be available 2020, and a 125 horsepower will be available in 2021.”

“Our basic tractor will have all the usual features found in most other tractors. The premium model line will have more features, especially on the software and hardware area. The zTractors will have no emissions and no hydraulics—just strong torque power.”

A four-hour charge will provide 6 to 10 hours of work in the field. “It requires only level two charging similar to car charging. “We are exploring a better battery, however currently it is the nickel ion technology,” Kvezereli said

“Horsepower is where we estimate the metrics for a tractor. What we think farmers care about is torque. In electric, to achieve higher torque is much easier than to achieve it with diesel power, and electric technology in general is very reliable for many types of tasks,” said Kvezereli.

The electric tractors keep the same three-point hitch as well as a PTO, both electrically operated.

“We build everything based on the requirements for the PTO and three-point hitch, and I think that’s what makes the Ztractor different from any other robotics companies that will provide a better tractor. It’s a general purpose and can replace a regular traditional tractor,” he said.

The main farming operations will be strawberry vineyards and vegetable operations. The tasks will include soil preparation and crop management. Harvest tasks are not yet available.

The prices for the tractors, calculated at $1,000 per horsepower, are similar to traditional tractors.

California Ag Today2019-06-05T15:01:14-07:00June 5th, 2019|

Strawberries Need Protection From Mites

New Predatory Species May Help Manage the Pest

By Patrick Cavanaugh, Editor

Two-spotted mites in strawberries continue to be one of the biggest problems every year.

“We see more of it coming from the nurseries, and this year is no exception,” explained David Peck, COO and Farmer of Manzanita Berry Farms in Santa Maria.

“What’s interesting to me is that in the years that we’ve been using persimilis predator mite, and that has been since the early ’80s, we don’t see the persimilis taking over two-spot populations as early in the season as we used to,” Peck continued. “Whether that’s weather-related, humidity-related, or if there’s a change in the genetics of the commercially available persimilis, I don’t know.”

David Peck

Peck said growers need to be aware of another trouble mite, the Lewis mite. Lewis mites have been seen on strawberries and raspberries in the Ventura area for some time, but growers appear to be noticing increased infestations in the recent years. Some growers have also seen them in Santa Maria in recent years, but they have so far not been reported from the Watsonville area. Considering the recent trend, growers might keep them in mind while scouting for pests.

“They’re out there, some places greater than others. Persimilis don’t like to eat Lewis mite. They are susceptible to all the same miticides. However, if you are relying heavily, on biologicals, you got to know if you have Lewis mite,” Peck said.

“I add fallacis predatory mites early in the season as a preventative for Lewis mite. The fallacis will eat two-spot or Lewis mite equally well and have done a pretty good job of keeping that initial early-season population of both mite species under control,” he explained.

Peck said that if there are mites in the strawberry nurseries, and the nurseries do not want to spray miticides, he understands that due to the possible development of pesticide-resistant mites showing up with plants.

“That’s a valid reason not to spray miticides at the nursery level. But there’s good data that fallacis will exist in those Northern California strawberry nursery areas, and they’re actually less expensive to procure than persimilis, and they survive through a wider environmental range than persimilis. They can handle colder, dryer, and hotter,” Peck said.

Some of the best data on strawberries and raspberries come out of Oregon State. It shows numerical data on how to put out the predatory mites, including how few you can put out.

“Personally, I’d be willing to spend an extra 50 cents or a dollar a thousand if the nurseries would inoculate their fields with fallacis. You might get a few predators coming in with your plants,” he said.

There is additional research on fallacis versus another predatory mite known as andersoni. Data shows that andersoni may be stronger than fallacis, thus doing a better job at controlling two-spotted mites.

Peck said that he has used andersoni on a test basis.

“I did not have enough of the predator to thoroughly complete a test in our organic fields, but I’m thinking that I will use that species for early season mite control.”

California Ag Today2019-01-30T16:53:58-08:00January 30th, 2019|

Strawberry Labor Issues May be Helped

New Technology in the Strawberry Industry Addresses Labor Issues

By Mikenzi Meyers, Contributing Editor

Once again, technology has taken crop production to the next level. This time, strawberry growers are reaping the benefits of technological advancements. Pete Molero and his team at Plantel Nurseries have come up with a transplanting machine that will address labor challenges in the strawberry field.

“We have come up with a transplanting machine that uses a 25-man crew to plant strawberries that have foliage on them and have a plug just like a transplant vegetable plug now,” Molero explained.

He further added that the machine can plant an acre an hour, a pace that would typically take 80 to 100 employees to achieve.

According to Molero, the process is simple.“The plug goes in, the plant gets dirt, and its set and ready to go.”

He described the root itself as a two-and-a-half to three-inch plug with first growth leaves at about three to four inches tall. As of right now, there is only one variety of strawberry available for the summer. However, new ones are being tested in hopes that this new equipment will continue to make improvements.

California Ag Today2019-01-23T16:37:26-08:00January 23rd, 2019|

Berry Industry Without Methyl Bromide

Berry Industry Must Now Work Smarter in Post Methyl Bromide Era

By Patrick Cavanaugh, Editor

The strawberry fruit production industry, with the exception of plant nurseries, has reached the point where methyl bromide is no longer available under any circumstances, and new alternatives or strategies must be found to protect strawberries from serious diseases.

The University of California is focused on a holistic approach, which includes the tried-and-true method of integrated pest management in this post Methyl Bromide era.

“None of the alternative fumigants are as good as methyl bromide,” said Mark Bolda, UC Cooperative Extension Farm Advisor for Santa Cruz County, who is working closely with growers on alternative methods. “So one area that we could focus on is different strategies at the time of planting. For example, strawberries have different chill times. You must add cold conditioning to give the plant more vigor.”

Mark Bolda

There are many questions. Could the colors of the plastic mulch that growers are using manage the temperatures of the soil? How about the amount of fertilizer that is being used?

“We need to start integrating these variables into the way we grow strawberries with the lack of fumigants that are as effective as methyl bromide,” Bolda explained. “We need to integrate all these things and others in order to grow berries with the lack of available fumigants that are as effective as methyl bromide.”

“It’s a little disappointing that here we are at zero-hour and we do not have this worked out,” he continued. “The University of California Cooperative Extension have had a number of meetings in my office, as well as other places where we get many people in the same room to try to figure out what we know and what we don’t know.”

“There’s a lot of smart people in the industry, and I know we can get on this and find solutions,” he said.

California Ag Today2021-05-12T11:05:06-07:00January 8th, 2019|

Strawberry Commission Oversees Valuable Crop

Strawberries in California

By Jessica Theisman, Associate Editor

Strawberries are California’s sixth most valuable crop which makes strawberry research a valuable tool for California farmers. Mercy Olmsted is senior manager of production research and education at the California Strawberry Commission. Growers in the California Strawberry Commission have invested over $28 million into research. These include areas such as diseases, insects, and weeds—all in an effort to help solve production challenges and boost economic gains.

“We are a commission that’s funded by the growers, and so we do research that meets their research priorities,” Olmsted said.

So far, $13 million has been invested in research to explore alternatives to methyl bromide. The commission says that strawberry farmers continue to invest in researching fumigant alternatives.

“We also work with researchers. We have a robust grant program, and we work with those researchers in order to assist them in their field trials,” Olmsted explained.

Some of their researchers are in house, and others are from the USDA and university researchers.

“We develop training programs for our growers because we work for the growers. We can contact them as often as we need to, and we are able to see how things and research priorities might change in the industry,” Olmsted said. “There are a number of facilities and a board that helps direct research priorities and any necessary changes.”

For more information on strawberry research being done by the California Strawberry Commission visit calstrawberry.com.

California Ag Today2021-05-12T11:05:07-07:00January 2nd, 2019|