August 28, 2019
Virologists have brewed up a new alphabet soup -- ToBRFV or tomato brown rugose fruit virus -- and much to the consternation of greenhouse tomato growers in the U.S., it’s headed their way, already sending out advance scouts in Arizona and California.
First discovered in Jordan in 2015, it moved on to Israel, Turkey, and Saudi Arabia, was spotted in Germany (2016) and Italy (2018) with likely occurrences reported (but not confirmed) in Chile, Ethopia, Sudan, Thailand, Peru, China, and the Netherlands. Now it’s being reported as widespread in Mexican greenhouses, just a hop and a skip across the border into neighboring states.
“We’ve had two incidents of it in California,” says Bob Gilbertson, who specializes in plant virology and seed pathology at University of California, Davis. “It was identified in a Santa Barbara County production greenhouse in September last year, confirmed by Kai-Shu Ling of the U.S. Department of Agriculture and by our plant pathologists. In that instance, all ToBRFV-infested and symptomatic plant material was voluntarily destroyed.
“Then, sometime in early August, we received suspect fruits from a market in Sacramento that had obtained them from Baja, Mexico,” he said. According to a report by Gilbertson and Zach Bagley of the California Tomato Research Institute, “They didn’t have necrotic lesions on the fruit --- there were white blotches --- but when we tested them, ToBRFV showed up.”
The acronym for tomato brown rugose fruit virus represents a new species of a well-known group of plant viruses, tobamoviruses. It’s highly virulent and seems to override existing genetic controls and researchers are noting: “Because of the rapid spread of this virus, it represents a major concern for worldwide tomato production because no tomato varieties are known to be resistant to it as it breaks or is not recognized by Tm-2 2 or any other resistance gene currently used to protect tomatoes genetically against tobamoviruses.”
Available information to date suggests ToBRFV is primarily a threat to protected culture (greenhouse or screenhouse) production although outbreaks in open fields have been reported in Mexico.
Because they grow more than 90 percent of the nation’s processed tomatoes but don’t grow for the fresh market, the California Tomato Growers Association is keeping a watchful eye on the situation, but suggests the greater concern belongs to the Western Growers Association.
Asked for comment, WGA’s Communications Manager Stephanie Metzinger replied by e-mail: “While we are aware of the situation, we do not have a statement to provide.”
One of WGA’s larger growers, Houweling’s in Camarillo, CA --- with 125 acres under glass and additional production facilities in Utah and Canada --- was willing to comment.
In a statement to Western Farm Press, they reported, “We’ve been diligent since the rumors and early news of ToBRFV, reassessing all our phytosanitary and operating protocols. We’ve eliminated packing products from other sites and opened satellite packing operations to manage partner grower products. Empty trucks get disinfected and cleaned, and in cooperation with our partners, we have eliminated the use of RPC shippers which we identified as a significant risk.”
‘EBOLA OF PLANT VIRUSES’
“We’re calling this one The Ebola of Plant Viruses,” says Gilbertson, first cautioning, “you’ve got to be vigilant about it because it spreads so rapidly,” and then cajoling, “but growers shouldn’t be paranoid and panicking because we have a number of ways to manage it.”
Because Arizona is a major hub of tomatoes imported into the U.S., it could be a bellweather for California growers and Gilbertson suggests everybody needs to be on heightened awareness.
Already recognizing that the best defense is a good offense, Wholesum Farms (Wholesum Harvest) with tomato greenhouses in Arizona as well as Sonora and Sinaloa, Mexico, is on alert with their beefsteak, cherry, Roma, and tomatoes-on-the-vine production.
“ToBRFV is a very serious threat to our production and we’re taking all necessary steps to insure we remain virus-free,” says Theojary Crisantes, Chief Operations Officer of the company with 60 acres of greenhouses, 220 acres of protected fields, and 325 acres of open field production who partner with other family-owned and -operated organic growers from Central Mexico through California.
“There has been no detected presence of the virus in any of our operations in Mexico or the USA and we’re taking extreme measures in sanitation going in and out of our greenhouses to make sure things stay that way.”
Not so lucky is the nearby NatureSweet operation that maintains 500 hectares in Mexico and 120 hectares in Arizona, with an annual production of 18 million plants, all under glass.
“We found rugose in one of our greenhouses in March of this year,” says General Manager Alexandro Briones Sanchez. “We spotted it from the first symptom and took immediate action, removing that row and five rows on either side and burning the plants and the coconut coir before performing a complete sanitizing.
“Some companies, when they find the first symptom, they’ll take a plant sample and send it to analysis which could take 48-72 hours. Because the virus is spread mechanically, by that time you may have touched all of your greenhouses if you’re not segregated and share labor. From our experience, if you make your decisions immediately when you find a plant with viral symptoms and remove it, it will be controllable at that point and pay off in the long run.”
Pathologist Gilbertson emphasizes the speed of the spread factor. “There is no insect vector here. It’s solely transmitted by contact, human touch or machines or tools. It’s extremely stable and can survive in dry tissue for years.”
Diagnostic seed testing is one of the keys to slowing down the spread of the virus, he says, advocating, “Management before, during, and after the growing season.” After the seed is tested, implement the safety factor, Plan B, which is to treat that seed with a 10% triple sodium phosphate solution “which will virtually eradicate any virus in the seed.”
GET THEM OUT EARLY
That’s what you can do before planting. During the growing season, constantly walk the rows looking for any kind of mosaic, a mottling on the leaves that will sometimes elongate. “Get those plants out early and don’t let them touch other plants to minimize the amount of inoculum. Workers need to be wearing clean protective clothing and dip their gloves and tools in TSP.”
After the growing season --- “Remove all the plants and spray down the inside of the house…all the benches, strings, ropes, tools, everything. This kind of sanitation is practiced in protected culture for bacterial canker, but the possibility of ToBRFV requires even more vigilance and intense sanitation.”
Gilbertson offers the following: “Although growers may have to spend more on sanitation protocol, this virus is hardly going to threaten tomato production in the U.S., protected or open-field. And although we have to up our game a bit, it shouldn’t cause a panic because we have a number of ways to manage it.”
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