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Table grape growers tour SJV

Joe Lazarra, a table grape grower from Australia, thrust a shovel into the dusty soil at the University of California Kearney Agricultural Research and Extension Center in Parlier, Calif., and liked what he saw.

“This soil is what we call gutsy,” he said, “a lot of organic matter; with good soil you’re 90 percent of the way there.”

Lazarra was one of about 100 foreign visitors taking a three-day tour of California’s grape production in the San Joaquin Valley in an effort to glean more information on how to produce the crop and guard against the vineyard pests.

They were among 300 participants in the 6th International Grape Symposium at UC Davis held prior to their tour, which included a visit to the Parlier center and updates on the European grapevine moth, its threat to California’s Central Valley and use of mating disruption for that pest in Italy.

They also saw a demonstration of a grape trellis installation as temperatures climbed to 107 degrees, heard about spray tips on using herbicides and about pests that could pose health concerns: spiders, scorpions and snakes.

The next day, they would travel to Visalia and a workshop on plant growth regulators, gibberelic acid, etephon for improving the color of red and black table grapes and experimental work toward the development of abscission agents for producing individual table grapes.

Alonso Puga, a grower of red globe grapes in Peru, said he was looking forward to that workshop and building on what he had already learned about new grape varieties.

Then it was on to Kern County and a visit to a packinghouse and other agricultural activities.

Michael Glassey, a medical entomologist with All-Pro Environmental Services and Pest Control in Hesperia, Calif., opened the Parlier visit with a discussion of spiders, scorpions and snakes — topics he has also discussed as an adviser to the military at Fort Irwin.

Those pests can be found in some California vineyards, and Glassey advised his listeners to take care around them, being careful to remain calm in any instance when bitten.

“Most spiders rarely bite people, and when they do they rarely make them sick,” he said. “I’ve been bitten by black widows 400 or 500 times and had no problems. But then I’m not sensitive.”

Glassey quipped, “My wife says I’m not sensitive to anything.”

He warned, though, that the bite of the black widow spider can be life-threatening to sensitive individuals and that medical assistance should be sought as soon as possible. Most at risk are those with high blood pressure.

He added that the bite of a brown recluse spider, not found in California, can cause severe local symptoms and medical attention is recommended. He suggested trying to find the spider that inflicted the bite and capture it. It can be helpful in diagnosis and treatment.

Glassey said he does not recommend – as some do – that people try to kill or capture a poisonous snake, because it can inflict venom long after it is dead and because trying to kill it can prevent the victim from remaining calm.

In California, the biggest threat from poisonous snakes comes from rattlesnakes. A gopher snake, more harmless, sometimes mimics the rattlesnake. Most poisonous snakebites – as many as 98 percent – come when someone tries to catch or kill a snake.

In the case of a snakebite, Glassey said, it is important to stay calm and to remove tight fitting clothing, shoes and jewelry because of swelling that can cause considerable harm.

He said the bite should be kept below the level of the heart and emergency care should be sought. No cold or ice should be applied to the bite.

Most of the scorpions found in California are among the larger species and their sting is no worse than a bee sting.

However, a bark scorpion, introduced into California in recent years, has a sting that can be life-threatening. A scorpion will sting repeatedly and should be removed quickly to avoid multiple stings. Particularly vulnerable to harm are children and older people, especially those with respiratory problems and heart disease.

Again, staying calm, seeking medical care and capturing the scorpion – if it can be done safely – is recommended.

Other topics and speakers for the Parlier meeting included:

• A presentation by Michele Melillo with the Agriproject Group in Italy on the effectiveness of mating disruption for Lobesia botrano, the European grape moth that is plaguing Napa Valley vineyards and has prompted a quarantine in Fresno and Merced counties in the Central Valley.

Melillo said the moth is a primary pest in the table grape regions of Mediterranean Europe. He said the number of plant hosts makes control difficult, and European growers have abandoned some pesticide applications because of restrictions and a growing interest in organic table grapes.

There were years in which as many as 20 spray applications were used. Now, it’s customary to spray six to eight times.

“The pest doesn’t like hot, dry climates, so that could be good news here,” Melillo said.

He said the use of pheromones to disrupt mating appears to be effective, but they must be in place before the flight stage of the moth.

• Walt Bentley, UC integrated pest management specialist with the Kearney Ag Center, praised Melillo’s work while cautioning that mating disruption is not being used in the quarantine area of Fresno County that covers 96 square miles.

“We want to avoid masking the presence of the pest,” he said. State trappers use the same pheromone to monitor where EGVM might be. If growers use pheromones for mating disruption, it nullifies the state traps. In Napa and other areas of the California’s North Coast grape growing regions, pheromones are used in mating disruption because trap numbers are so high. This represents a breeding, possibly established, EGVM population.

Bentley said the quarantine is “creating headaches for all grape growers, not just growers of table grapes.” However, he remains optimistic the pest can be eradicated in the region. To date, 10 moths have been trapped, a far cry from the thousands in the Napa Valley.

He said growers should note that financial assistance is available to those located in the core quarantine area from the National Resource Conservation Service to help offset the cost of insecticides.

• Kurt Hembree, weed management UC farm advisor, Fresno County, talked of how to achieve the greatest efficiency – without causing harm – when applying herbicides.

He said it is important that treatments be timely and that appropriate spray nozzles are used. Treatment should be within one or two weeks of a rain event of at least a quarter of an inch, he said. “Weeds are easier to kill when they are small,” Hembree said, adding that if the soil becomes dry after weeds emerge they can be more difficult to kill.

“Don’t wait to spray big weeds, because they will have dense foliage, requiring higher spray volumes, higher herbicide rates and follow-up treatments.”

Nozzle choice affects droplet size and that can be a factor in drift and the amount that actually reaches the target site, Hembree said.

TAGS: Grapes
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