An early October rainstorm in the San Joaquin Valley provided UC viticulture specialist Matthew Fidelibus an ideal opportunity to evaluate the effectiveness of plastic vine covers for protecting late-season table grapes from inclement weather.

Fidelibus, who is based at the Kearney Agricultural Research and Extension Center, installed the covers in September on a Redglobe vineyard near Easton. Some farmers choose to grow late season table grapes – such as Autumn King, Crimson Seedless and Redglobe – to market in the fall when prices are typically highest. However, they run a greater risk of being rained on. Exposure to moisture within six weeks of harvest can cause rots and molds to render the grapes worthless.

Many growers with late-season table grapes cover their vines with sheets of plastic film to protect them from rain. Growers may choose between a relatively transparent green film, or a more opaque white film, but data distinguishing the differences the two films might have on vine physiology or fruit quality at picking, or after storage, are not available. Buying, installing and removing the plastic is very expensive, so Fidelibus is working to provide growers with objective information about the effects of the different films. Growers can track the progress of the trial in real time by following Fidelibus’ Twitter feed, http://twitter.com/grapetweets.

Five days after the trial was installed, a winter storm rolled into the San Joaquin Valley, dropping nearly an inch of rain on the table grape trial. As expected, the fruit on the covered vines stayed dry while the uncovered grapes were soaked, however, the covers posed some problems of their own.

“In some places we found pools of water on the plastic covers,” Fidelibus said. “In fact, the weight of the water displaced the covers, exposing the vines in some places. A few pools apparently grew until reaching a vent hole, releasing a water stream powerful enough to wash soil from roots.”

After the storm, the soil under the covered vines remained dry, but wind and sun quickly dried the grape clusters and soil around uncovered vines.

Data loggers in the grapevine canopies are collecting temperature and humidity readings – measures that Fidelibus will use to help describe the effect of the different covers on the environment within the grapevine canopies. He also installed atmometers, special instruments that help determine the canopy’s “evaporative potential.” Research has already shown that the greater the evaporative potential, the lower the incidence of bunch rot.

“The covers protect the grapes from rain, but when it’s not raining, they create a hotter and more humid environment under the plastic,” Fidelibus said. “The high temperatures can damage some of the vines’ leaves, and condensation on the inside of the plastic can precipitate onto the grapes. We want to know if either film provides a superior environment for table grapes. These data will also serve as a baseline against which new covering systems may be compared.”

UC integrated pest management entomologist Walter Bentley has received the UC Agriculture and Natural Resources Distinguished Service Award for Outstanding Extension in recognition of his 34-year career dedicated to the development and delivery of practical, relevant and sensible pest management programs to the people of California.

Bentley was named the UC Cooperative Extension entomology advisor for Kern County in 1977. In 1994, he was promoted to his position with the IPM program and relocated to the Kearney Agricultural Research and Extension Center in Parlier. Bentley was nominated for the award, a statewide honor, by his colleague, UC IPM nematologist Peter Goodell.

Goodell said Bentley has had only two driving forces in his career: create practical yet high quality entomological knowledge based on science and direct that knowledge to make a difference in the lives of the people he serves.

"Mr. Bentley's career represents the best UCCE's faculty has to offer: unselfish service, loyalty to his peers and clientele, intellectual honesty, dedication to the mission of UCCE and a genuine love for his work," Goodell wrote.

UC subtropical horticulture specialist Mary Lu Arpaia, who is based at the Kearney Agricultural Research and Extension Center, was one of four UC specialists who traveled to Sarajevo Oct. 24-28 at the request of local officials to present a condensed version of the UC Postharvest Technology Short Course. Nearly 100 participants from 11 countries attended the program, which included lectures and a field tour. Simultaneous translation was offered in Bosnian and Russian.

“To me it was a very interesting experience,” Arpaia said. “The participants were very engaged in the course and asked lots of questions that were spot-on in terms of sharing practical information. They were very keen to get information on the ‘how to’ and solving practical situations."

Mary Reed of the UC Postharvest Technology Center said interest in the short course was remarkable given that the first estimate from planners was for 25 participants.

“Interest just kept growing and growing as word got around,” Reed said. “Given the challenges of traveling in the region, acquiring visas, and obtaining agency permissions, the participants really had to overcome significant obstacles in order to attend.”

Arpaia said the four-days she spent with Eastern European farmers in an area that suffered bitter ethnic conflicts in the 1990s also made a profound personal impression.

“I had been aware of the war in the Balkans but never fully appreciated the impact of that war on people’s lives,” she said. “You can still see the physical scars of the war – mortar shell scars on buildings, burned and abandoned buildings – and, more dramatically, hear the angst of the people when they talked about those times. It is another example to reflect upon in terms of how lucky we are in the U.S. and that we need to forever be vigilant not to allow animosities to fester due to ethnicity, religion etc.”

The growing interest in valley pomegranate production was demonstrated by a standing-room-only crowd of more than 130 farmers, pest control advisers and industry representatives at the San Joaquin Valley Pomegranate Meeting Nov. 29 at the Kearney Agricultural Research and Extension Center.

UC Integrated Pest Management Program entomologist Walt Bentley opened the meeting with an overview of the crop's most serious insect pests. Bentley suggested growers focus on omnivorous leaf rollers and cotton aphids. Ash whiteflies had been a pomegranate problem in the 1980s, until UC scientists introduced a natural enemy, encarsia, in 1991.

"This was an amazing biological control success," Bentley said.

Bentley admonished growers to protect the beneficial insects on their farms.

"Ash whitefly will eat you alive if you take encarsia away," he said.

Today, omnivorous leaf rollers are the key pomegranate pests. They move into the crop from weedy areas, feed on leaves, and unlike in grapes and peaches, will also feed inside pomegranate fruit.

"If you're not monitoring for it with pheromone traps you're going to get stung and it will cost you money," Bentley said. He suggested traps be placed in orchards in February.

Another important pest of pomegranates, cotton aphids, reduces crop yields and contaminates the fruit by excreting honeydew. Bentley described crop protection strategies for these pests plus ants, fork-tailed bush katydids, grape mealybug, false chinch bug, leaf-footed plant bug, citrus flat mite, navel orangeworm and filbert worm.

Kearney plant pathologist Themis Michailides presented research results from his lab on black heart disease of pomegranates. Black heart is of particular concern because it causes no external symptoms; consumers who encounter the unappealing blackened fruit inside may be reluctant to try pomegranates again in the future. The research focuses on the identification of the fungus species that cause black heart, understanding the infection process, and developing procedures to manage the disease. Michailides has concluded that the main cause of black heart is Alternaria spp., fungi that are very abundant in nature and cause diseases in many crops. Further research was conducted to determine when infections take place in order to properly time the management application.

"We found that the 'Achilles heel' for infection by Alternaria is the open pomegranate flowers," Michailides said. "Amazingly, infections start at bloom, remain latent in the fruit and develop later in season as the fruit matures."

Jeff Moersfelder, the greenhouse/nursery manager and pomegranate point person for the USDA's National Clonal Germplasm Repository in Davis reviewed some of the pomegranate varieties the program offers to nurseries. The selections revealed arils (seed pods) with color ranging from pale yellow to inky red. He described sweet varieties that evoke cherry Slurpee and pineapple Lifesavers, and tart varieties with astringency akin to dry wine.

Among Moersfelder's favorites are Parfianka, a well balanced, sweet-tart pomegranate with excellent grenadine flavor and soft seeds, and Ariana, which has deep red rind and dark red arils. The darkest variety in the Davis collection is Kara-Gul, a cultivar from Azerbaijian. This variety, however, is more susceptible to heart rot. Moersfelder also characterized spice type pomegranates from the Western Himalayas, which are dried and used as condiments in Indian food, and ornamental varieties, many of which produce beautiful flowers but no fruit.

The program closed with USDA emeritus researcher Claude Phené's description of a pomegranate irrigation, fertigation and nitrogen use efficiency trial under way at Kearney. Two trees in the trial are growing in the station's weighing lysimeter, a huge subsurface scale that allows scientists to determine exactly how much water a plant is using. The study aims to maximize water fertigation uniformity, improve nitrogen efficiency and minimize nitrogen leaching below the trees' root zone.

The meeting was organized by UC Cooperative Extension farm advisors Maxwell Norton, Bob Beede, and Richard Molinar.