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Agri-Bytes
June 2009
In This Edition:
- 'Worst' tomato virus prompts talk of plant movement restrictions
- El Niño may mean fewer hurricanes this season
- Two new peach varieties join fresh-market offerings
'Worst' tomato virus prompts talk of plant movement restrictions
A disease that at least one plant pathologist calls the “worst virus of tomatoes we know” continues to expand its reach in California since its initial discovery in the state in 2007.
“I have seen what this virus does in certain parts of the world, and it’s scary,” says Bob Gilbertson, a University of California, Davis, plant pathology professor. “I want to emphasize that this has been in tropical areas that have whiteflies year-round.”
Although tomato yellow leaf curl virus still has only been found in a few scattered residential gardens and commercial tomato fields in Imperial and Riverside counties, it has prompted at least one county to consider plant movement restrictions.
Fresno County has proposed three options, two of which would require increased inspections of tomato transplants, says county agriculture commissioner Carol Hafner.
They are a protected area, where plants would be inspected moving in and out of the county; a non-protected area that would allow free movement with the transplants only having to meet the state’s nursery regulations; and a county ordinance, which would require additional inspections of transplants.
The protected area proposal also would require that inspectors survey 10 percent of fields where transplants from non-protected areas were planted. The county has about 130,000 acres of tomatoes.
The county ordinance would require that 10 percent of all incoming transplants—whether commercial or retail—be inspected annually.
By some estimates, between 1,800 and 2,000 loads of tomato transplants enter the county each year.
The protected area and county ordinance would annually cost $43,000 and $40,000, respectively.
The county ag commissioner’s office already has cut staffing and hours and has no money to implement either program. So Hafner says the industry would have to provide the funding, should it decide on either one.
The three proposals would replace an exterior quarantine that the California Department of Food and Agriculture has proposed discontinuing.
In addition, CDFA would have to conduct a statewide survey to identify localized infections so other states would accept the exterior quarantine.
Without a survey, Hafner says other states could challenge the quarantine.
Should the exterior quarantine be dropped, individual counties could decide on what type of restrictions, if any, they would place on tomato transplant movement, she says. And transplant shippers could face a hodgepodge of county regulations.
Tomato yellow leaf curl virus was first detected in California in a Brawley High School greenhouse in 2007 by University of California Cooperative Extension farm adviser Eric Natwick. The plants were started from seed.
Surveys have since detected it in a few scattered fields and gardens in imperial and Riverside counties.
Ozgur Batuman, one of Gilbertson’s graduate students, detected one infected plant in a Merced County tomato field in 2008. He found it as part of his research on the more ubiquitous tomato spotted wilt virus.
But Gilbertson says he believes it was an isolated event and was a transplant moved in from elsewhere.
Tomato yellow leaf curl virus showed up in northern Mexico during the 2005-06 season and has since been found in Texas, Guatemala, Louisiana, Georgia, Texas and Arizona, Gilbertson says.
The virus is spread by Bemisia tabaci, or the desert-resident greenhouse or silverleaf whitefly, and not the sweet potato whitefly.
“What’s very bad is the whiteflies can acquire and transmit the virus very quickly—in minutes—and transmit it for the rest of their lives,” Gilbertson says.
The disease is not known to be seed transmitted. Whiteflies typically only fly a few miles, so most of the long-distance spread of the disease is through movement of infected plants, he says.
Plants infected with tomato yellow leaf curl virus are stunted and have a distinctive upright growth, sometimes called a bonsai symptom because they resemble a bonsai tree.
Leaves also are stunted, curled upright and turn a bright yellow with the veins remaining green.
If the plants are infected early in the season, they are “basically done for,” Gilbertson says. Later infections
For more information, visit:
• University of California Integrated Pest Management—TYLCV
• Curly top virus and tomato yellow leaf curl virus
• University of Florida Institute of Food and Agricultural Sciences
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El Niño may mean fewer hurricanes this season
Credit El Niño for what is predicted to be a slightly below-normal hurricane season this year.
That was the prognosis from William Gray, a Colorado State University weather forecaster with more than a quarter century of experience.
Gray and fellow forecaster Phil Klotzbach predict 11 named storms between June 1 and Nov. 30. Of those, five will become hurricanes. And of those, two will develop into major hurricanes—Category 3, 4 or 5 with sustained winds of 111 mph or greater.
That compares with long-term averages of 9.6 named storms, 5.9 hurricanes and 2.3 major hurricanes annually, according to a university news release.
In May, the National Oceanic and Atmospheric Administration, which oversees the National Weather Service, called for a 50 percent chance of a near-normal hurricane season.
Governmental forecasters gave a 70 percent chance of nine to 14 named storms, of which four to seven could become hurricanes, including one to three major hurricanes of Category 3 or stronger.
The Colorado team says there is a chance that a weak El Niño weather pattern will develop later this summer or early this fall.
El Niño produces oceanic cooling in the tropical Atlantic regions, decreasing conditions conducive to hurricane formation, Gray says.
If that should occur, look for fewer hurricanes to form.
The Colorado team also updated its U.S. landfall probabilities.
"The probability of a major hurricane making landfall along the U.S. coastline is 48 percent compared with the last-century average of 52 percent," Klotzbach said in a news release.
Here are a few other of their probabilities:
• A 28 percent chance that a major hurricane will make landfall on the U.S. East Coast, including the Florida peninsula (the long-term average is 31 percent).
• A 28 percent chance that a major hurricane will make landfall on the Gulf Coast from the Florida panhandle west to Brownsville, Texas (the long-term average is 30 percent).
To view all their probabilities, visit http://www.e-transit.org.
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Two new peach varieties join fresh-market offerings
The Agricultural Research Service has released two yellow-fleshed freestone peach varieties best suited to the fresh market.
They were developed at the Appalachian Fruit Research Station in Kearneyville, W. Va., and released through a cooperative effort with Adams County Nursery Inc. in Aspers, Pa.
Both varieties produce fruit about 3 inches in diameter and are classified as dessert peaches designed for the fresh market.
SummerFest is a mid-season variety with good fruit firmness and an upright-growth pattern, according to a news release. The fruit has a balanced sugar-to-acid ratio.
Upright growing trees lend themselves to high-density plantings of about 8 feet apart.
FlavrBurst has similar sugars, but is lower in acidity than typical peach varieties.
Fruit ripen in mid-season and have good firmness at maturity.
It produces a standard-type tree.
The two new cultivars were released this spring to commercial growers and university test sites for further evaluation.
Consumers can expect to see these varieties on the market in 2011.
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