Some of the University’s research and educational outreach efforts are described below.

• Micronutrients may hold promise for preventing Pierce’s disease
• Geneticist sleuthing sources of resistance to Pierce’s disease
• IPM advisor pioneers research on glassy-winged sharpshooter biology
• Pruning and freezing hold promise for treating grapevines with Pierce’s disease
• Scientists search for ways to curb resurgence of Pierce’s disease in Temecula wine industry
• If you love the shade, you’ll be dismayed by the glassy-winged sharpshooter
• UC Cooperative Extension works closely with farmers to keep Pierce’s disease at bay
• San Joaquin Valley vineyards imperiled by glassy-winged sharpshooter
• Scientists work to protect stream habitat in northern vineyards while eliminating blue-green sharpshooters
• Ecologists study role of vineyard stream vegetation for Russian River Basin wildlife

Micronutrients may hold promise for preventing Pierce’s disease

A UC Davis plant pathologist is conducting experiments to determine whether infection by the bacterium responsible for Pierce’s disease can be prevented by boosting grapevines’ levels of essential plant micronutrients, such as zinc, iron and molybdenum. "We’ve already established in the laboratory what concentrations are toxic to the bacteria," said professor Bruce Kirkpatrick. "What we need is to develop a system that gets those nutrients into the grapevine to protect it from infection." In an experimental vineyard at UC Davis, Kirkpatrick has been looking at a number of methods of introducing the nutrients into vines -- foliar applications to leaves, tiny plastic screws inserted into the vines, hand-held injection devices and irrigation drip lines. The strategy is to protect the plants against infection, rather than to treat them after the fact. Once bacteria enter the root system, they become more difficult to treat because water travels up through infected xylem tissue toward respiring grape leaves. An advantage of inoculating vines with nutrients, Kirkpatrick said, is avoiding the stigma associated with antibiotic use. Encouraged by results from laboratory analyses, field trials are now under way. For more information, contact Kirkpatrick at (530) 752-2831, bckirkpatrick@ucdavis.edu. Tip by John Stumbos, (530) 754-9554, jdstumbos@ucdavis.edu.

Most California grape growers have probably never heard of muscadine varieties such as Southland, Magnolia, Carlos or Dixie, but locked within these grapevines may be the salvation of the state’s table, raisin and wine grape industry. While short-term strategies to cope with Pierce’s disease focus on management of the sharpshooter and controlling the pathogenic bacteria it carries, the only sure-fire, long-term approach will be to build disease resistance into the genetic fabric of the commercial varieties grown in California. The unfamiliar sounding varieties like Southland are of the genus and species Muscadinia rotundifolia, while the more familiar Thompson Seedless, Chardonnays, Cabernets and Merlots are cultivars of Vitis vinifera. Muscadine grapes, native to the southeastern United States, taste peculiar and make poor wine, but they are resistant to Pierce’s disease. Grape breeding is a notoriously slow process, but UC Davis professor of viticulture and enology Andy Walker reports progress developing a fertile "bridge" hybrid from M. rotundifolia to transfer the gene -- or genes -- of resistance into vinifera grapes. Walker plans to screen seedlings’ genes for resistance to Pierce’s disease in order to bypass the field testing process. Genetic screening may reduce the time required for creation of resistant varieties from 30 years to 10 years. For more information, contact Walker at (530) 752-0902, awalker@ucdavis.edu. Tip by John Stumbos, (530) 754-9554, jdstumbos@ucdavis.edu.

IPM advisor pioneers research on glassy-winged sharpshooter biology

Five years ago, UC scientist Phil Phillips began studying the biology of glassy-winged sharpshooters, insects newly identified in Ventura County citrus trees. "It was more of a novelty back then," he said. "I was concerned because it was known to transmit disease-causing bacteria in the southeastern United States." The integrated pest management advisor’s work has yielded valuable data about the pest now threatening agricultural and ornamental plants throughout California with lethal plant diseases. Most significantly, the sharpshooter spreads bacteria that cause Pierce’s disease in grapes, leaf scorch in oleander and almond, and variegated chlorosis in citrus. "I’ve gathered some very good information," Phillips said, "in terms of generation times, hosts that it feeds on, key parasites in the egg stage and some level of biological control." The pest, he said, survives cold winter temperatures in its adult stage, making it reasonably hardy. Normally it lives in treetops. "When cold weather comes, sharpshooters drop to the ground like bombs and hang out in the leaf litter until it warms up," he said. Phillips traveled with colleague Serguie Triapitsyn to northeastern Mexico, where they collected a new natural enemy of the glassy-winged sharpshooter. However, he said, the sharpshooter out produces its enemies. A systemic insecticide, imidacloprid, will kill the sharpshooter, he said, but probably not fast enough to prevent it from transmitting the bacteria that cause diseases. "Right now, we don’t know what’s going to stop it," Phillips said. For more information contact Phillips at (805) 645-1457, paphillips@ucdavis.edu. Tip by Jeannette Warnert, (559) 225-5611, jwarnert@uckac.edu.

Pruning and freezing hold promise for treating grapevines with Pierce’s disease

Researchers in the laboratory of UC Berkeley professor Alexander "Sandy" Purcell have found that pruning and freezing may, in some cases, save grapevines afflicted with Pierce's disease. Purcell, one of California's leading experts on the devastating disease, has found that heavily pruning grapevines in winter helps eliminate the Xylella fastidiosa bacterium, which causes the disease. "Our early results with pruning are promising," Purcell says. "If a grower is faced with an infected crop, heavy pruning in the winter may mean he'll lose some crop, but he won't lose all of the time required to replace the vine. However, we need more data on how vine age and variety affect the success of pruning before we make specific recommendations." Also in his lab, graduate researcher Helene Feil has found that freezing dormant vines in the lab can rid them of the disease. "Although growers cannot intentionally freeze vines to cure plants of Pierce's disease," Purcell said, "these experiments provided unexpected indications that it is the vine's response to cold temperature, not just the temperature alone, that is necessary to kill the Xylella bacteria." His lab is now trying to identify how freezing changes the grapevines so that the bacteria die. For more information contact Purcell at (510) 642-7285; purcell@nature.berkeley.edu or see his website at http://www.cnr.berkeley.edu/xylella/purcell/research.html. Tip by Jill Goetz, (510) 643-1042, jgoetz@nature.berkeley.edu.

Scientists search for ways to curb resurgence of Pierce’s disease in Temecula wine industry

The glassy-winged sharpshooter, first identified as a major carrier of Pierce’s disease in the Temecula Valley in 1997, has already caused an estimated $1.2 million in damage in this southwest region of Riverside County. UC Riverside scientists are evaluating possible natural enemies to the glassy-winged sharpshooter in hopes of controlling the insect without pesticides. In addition to biological control strategies, they are investigating the use of pesticides and physical barriers to prevent the insects from flying into vineyards. Researchers Matthew Blua and Rick Redak are exploring the use of a soil-applied insecticide that can be used by growers to reduce sharpshooter numbers and alter their feeding behavior while scientists work on slowing the spread of Pierce’s disease. For more information contact Blua (909) 787-4733, matthew.blua@ucr.edu, or Redak (909) 787-7250, richard.redak@ucr.edu. Tip by Kathy Barton, (909) 787-2495, barton@ucrac1.ucr.edu.

If you love the shade, you’ll be dismayed by the glassy-winged sharpshooter

The shade of a backyard, park, parking lot or street tree is an unwelcome retreat if the canopy is infested with glassy-winged sharpshooters, a relatively new pest to California that scientists believe could spread through much of the state. The sharpshooters excrete water droplets that eventually wet people, picnics, cars and sidewalks underneath. "Sharpshooters have to filter out minerals and amino acids from liquid sucked from plants," said Phil Phillips, UC integrated pest management advisor based in Ventura County. "They have to filter so much water to get adequate nutrition that it produces a fairly sizable droplet of water about every three minutes." By autumn, the leftover salts from water dripped and evaporated make infested trees look like they’ve been whitewashed. Ash, citrus, sycamore, macadamia and crape myrtle are among the sharpshooters’ favorite haunts. For more information contact Phil Phillips at (805) 645-1457, paphillips@ucdavis.edu. Tip by Jeannette Warnert, (559) 225-5611, jwarnert@uckac.edu.

UC Cooperative Extension works closely with farmers to keep Pierce’s disease at bay

University of California Cooperative Extension farm advisors are enlisting the help of farmers to quickly identify glassy-winged sharpshooters should the new pest make an appearance in Northern California’s famed grape-growing counties. "We have to undertake a strong education campaign targeting growers and ornamental nurseries to ensure they will recognize it and then try to eradicate it as fast as possible," said Lucia Varela, UC integrated pest management advisor based in Sonoma County. The campaign continues a four-year effort to educate farmers about Pierce’s disease symptoms, management and insect carriers. Varela wrote an 11-page reference document for growers detailing the threat. Over the years, UCCE farm advisors have held a series of workshops in North Coast counties. "We have an ongoing extension program designed to teach growers the epidemeology of the disease, the lifecycle of the insect carriers and the movement of the disease from riparian plants to grapevines," said Rhonda Smith, viticulture farm advisor for Sonoma County. In the fall, when symptoms of the disease are most evident in infected grapevines, the topic of Pierce’s dominates the advisors’ one-on-one consultations with farmers regarding grapevine diseases, according to Ed Weber, UCCE viticulture advisor for Napa County. This winter, he said, a new publication will be available to guide farmers in the delicate process of managing riverbank vegetation to minimize the threat of Pierce’s disease. For more information contact Rhonda Smith at (707) 565-2621, rhsmith@ucdavis.edu, or Ed Weber at (707) 253-4221, eaweber@ucdavis.edu. Tip by Jeannette Warnert, (559) 225-5611, jwarnert@uckac.edu.

San Joaquin Valley vineyards imperiled by glassy-winged sharpshooter

With no effective control strategy in sight, scientists fear glassy-winged sharpshooters will spread throughout the agriculture-rich San Joaquin Valley, threatening nearly 800,000 acres of table, raisin and wine grapes – 72 percent of the state’s vineyards – with the deadly Pierce’s disease. Already, the pest has been identified in Kern and San Joaquin counties. Pierce’s disease has been a problem in the San Joaquin Valley for the last 80 years, according to Bill Peacock, UC Cooperative Extension viticulture farm advisor for Tulare County. The most susceptible vineyards are those on the outskirts of grape-growing areas, next to pastures or riparian areas. "There are some areas in the county where we can’t plant because Pierce’s disease wipes vineyards out," he said. The glassy-winged sharpshooter, however, appears to be a stronger flyer than the pests that currently spread Pierce’s disease in the San Joaquin Valley and it has a wider host range. "I’m concerned that this will be much more serious," Peacock said. For more information contact Peacock, (559) 733-6363, wlpeacock@ucdavis.edu. Tip by Jeannette Warnert, (559) 225-5611, jwarnert@uckac.edu.

Scientists work to protect stream habitat in northern vineyards while eliminating blue-green sharpshooters

In Northern California, vineyards are often located near rivers and streams, and the vegetation along these waterways is prime habitat for blue-green sharpshooters, carriers of Pierce’s disease. Some vineyardists, in their zeal to prevent the disease from striking their grapevines, have been clearing riparian vegetation, with serious implications for stream health and wildlife. Researchers from UC Berkeley and UC Cooperative Extension in Sonoma County are studying how to reduce the prevalence of blue-green sharpshooters while protecting riparian vegetation. They have found that removing certain plants and planting others can dramatically reduce the insects’ prevalence. Plants that the sharpshooters favor and should be removed include wild grape, Himalayan blackberry, French broom and periwinkle. Plants not likely to attract the insects include oaks, California bay laurel, alder, maple, ash and red willows. For more information contact professor Joe McBride, (510) 643-8074, jrm@nature.berkeley.edu or professor Alexander "Sandy" Purcell at (510) 642-7285, purcell@nature.berkeley.edu. Tip by Jill Goetz, (510) 643-1042, jgoetz@nature.berkeley.edu.

Ecologists study role of vineyard stream vegetation for Russian River Basin wildlife

When vineyardists clear streamside vegetation to keep blue-green sharpshooters at bay, they may inadvertently harm beneficial wildlife as well. Researchers with the UC Integrated Hardwood Range Management Program are studying the importance of these riparian corridors for wildlife habitat and migration. They are comparing the presence of a variety of wildlife species in corridors of different widths. The research suggests that wildlife prefer wider corridors around the riparian zones to narrower ones, and that when these routes are broken or fragmented, animals may not be able to migrate through them. Using geographic information systems technology, the researchers are also determining how far streams must be set back from vineyards for streamside plants and wildlife to thrive. For more information contact Adina Merenlender, (707) 744-1270, adina@nature.berkeley.edu. Tip by Jill Goetz, (510) 643-1042, jgoetz@nature.berkeley.edu.