- Author: Lauren Fordyce
The glassy-winged sharpshooter is a large leafhopper that can transmit several important, often fatal, plant diseases in California. This includes Pierce's disease of grape, alfalfa dwarf, almond leaf scorch, and mulberry leaf scorch. Pierce's disease is of most concern in California since the state accounts for about 94% of U.S. grape production.
Pierce's disease of grape has been reported in many counties throughout California. View a map of the current distribution of the pathogen. Glassy-winged sharpshooter adults are ½ inch long and dark brown to black with light-colored spots on their heads. Eggs are laid in masses under the leaf surface, resembling a greenish blister. Once the eggs hatch, the egg mass turns brown and remains as a scar on the leaf.
What can you do?
Glassy-winged sharpshooter feeds on many woody plants as well as annual and perennial herbaceous plants. It is common to find this invasive insect on acacia, avocado, eucalyptus, citrus, crepe myrtle, heavenly bamboo, grape, photinia, pittosporum, hibiscus, periwinkle, xylosma, some roses, and many others. Inspect plants for this pest, especially new shoots or growth. Use yellow-sticky card traps to monitor their populations.
If you find glassy-winged sharpshooter in an area not currently known to have this pest, immediately call the California Department of Food & Agriculture Pest Hotline at 1-800-491-1899, or contact your local agricultural commissioner's office.
To learn more about this pest and the diseases is transmits, visit Pest Notes: Glassy-winged Sharpshooter.
- Author: Tony Nunes, UC Master Gardener
By Tony Nunes, U.C. Master Gardener of Napa County
Knowing basic botany and grapevine structure and selecting a variety and rootstock suited to the location can help vineyard owners succeed. Master Gardeners call it putting the right plant in the right place.
We are fortunate to live in a region with soil types and microclimates that produce world-class wines. Just like commercial vineyard managers, home vineyard owners need to make decisions based on their unique site, goals and conditions and make adjustments driven by Mother Nature throughout each growing season.
It starts with a vineyard management plan for the season. Napa Valley has kicked off the year with rainfall amounts and low temperatures not seen in many years. Determining pruning dates is the first step. In some places, pruning has already started as vineyard managers allocate their resources throughout the valley.
Home vineyard owners may have the flexibility to delay pruning, which in turn delays bud break and minimizes the potential for damage from a late frost. Some people make two passes, first to remove last year's old canes, then to make the final command decision: the pruning of buds created during the 2016 growing season that will produce the crop for this year's harvest.
As our growing season progresses, days get longer, soil temperatures rise and grapevine sap begins to flow. This awakening from winter dormancy is one of many milestones of the growing season.
One element of integrated pest management is a plan for controlling powdery mildew (Uncinula necator) and botrytis (Botrytis cinerea) from bud break to veraison, the color change in grapes that signals the onset of ripening. The spores that cause powdery mildew or botrytis are ubiquitous in Napa Valley vineyards.
Powdery mildew infections from the previous year appear as a blue fungus on individual berries or clusters. Botrytis affects the internal tissues of the berry or the entire cluster. Berries split and fungal spores can grow out of split skins. The spores from infected clusters are distributed easily by wind. Spores can survive the winter on the grapevine bark and cause infections the following year.
Early in the growing season, vine shoots grow rapidly. Like a jack-in-the-box, buds produce shoots and a self-pollinating flower blooms to produce the year's crop. Bloom and fruit set are critical periods driving yield and fruit quality. Temperature swings and rain are not welcome during this time.
Grapevines do not required special fertilizers but should be kept in balance with nutrients available in the soil. Too much nitrogen in the soil can cause vines to produce excess canopy, creating issues with pest management and crop quality.
When applying fertilizer, first ask yourself why. Testing can help you determine what the vine needs. The first test of the growing season, petiole testing, should be performed after fruit set. Petioles connect leaf blades to the vine shoot. Samples of 25 to 50 petioles are selected for each block and tested to determine what nutrients might be deficient or present in excess. Fertilizers are then applied according to the specific needs of that block.
Grape clusters need leaves and sunshine to ripen the crop. Additionally, new buds require sunshine to produce energy for next year's crop. Managing the amount of leaves and their health is referred to as canopy management.
Removing leaves at the base of the canes surrounding grape bunches allows for better sunlight penetration and airflow. To guide decisions about leaf removal, growers observe weather conditions and how the vineyards are oriented to the sun. Leaf removal on the west side facing the afternoon sun is limited during July and August to minimize sunburn and bunch rot. Home grape growers may also need to observe their microclimates or placement of buildings when determining how to manage the canopy.
Irrigation decisions also affect canopy health. Vineyard managers monitor soil moisture levels and visual clues from leaf blades and tendrils during the early season's rapid shoot growth, flowering and fruit set. When irrigation is needed, it is best to irrigate deeply according to the site's soil-moisture holding capacity.
Roots don't grow in dry soil. The goal is to encourage roots to grow as deeply as possible given the site's soil conditions, with just enough water stress to produce high-quality fruit.
Home vineyard owners are generally optimists or at least try to be. Each year, they look forward to a successful harvest, drawing on the knowledge gained from previous growing seasons.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
- Author: Jeannette E. Warnert
Anaheim boasted a thriving wine industry in the late 1800s, before an unnamed affliction killed 40,000 acres of the grapevines and put 50 wineries out of business. The problem was later found to have been Pierce’s disease of grapevines. Would Anaheim be wine country today if it weren’t for Pierce’s disease? Probably not, but the sad fate of this Southern California wine industry underscores the importance of controlling the disease and the insects that spread it in California’s thriving grape growing regions.
GWSS has turned out to be a very efficient vector of Xyella fastidiosa, the bacterium that causes Pierce’s disease in grapes. When GWSS made their way to places where scientists believed the bacterium didn’t exist, such as Kern County, grapevines began to express symptoms of the disease. The county agricultural commissioners in the San Joaquin Valley have been working tirelessly over the last 10 years to keep glassy-winged sharpshooters out of grape growing regions to protect a very valuable economic driver. In Fresno County alone, where grapes are the No. 1 agricultural commodity, the crop was worth $961 million in 2011.
Despite the efforts to contain GWSS in Fresno County, the pest is spreading very gradually south and east of the Fresno-Clovis metropolitan area into commercial vineyards and orchards.
“Cooperation by urban residents where we find GWSS has been great,” said Fred Rinder of the Fresno County Agricultural Commissioner’s office. Nevertheless, in 2012, GWSS was found spreading out in Kerman, Parlier, Sanger and Kingsburg.
Stephen Vasquez, UC Cooperative Extension advisor in Fresno County, fears local grape farmers have become complacent about glassy-winged sharpshooter and Pierce’s disease, even though all grapes are susceptible. The best way to control its spread, he said, is to monitor and manage sharpshooter vectors and remove and replace vines that have tested positive for Xylella fastidiosa.
“Be vigilant. Learn the symptoms and train crews and workers,” Vasquez said. “Pierce’s disease has been around for a long time and GWSS has been here more than a decade, but we still haven’t had that marriage of the two. That is potentially devastating.”
The UC IPM website has extension information on glassy-winged sharpshooter and Pierce’s disease.
- Author: Jeannette E. Warnert
Anaheim boasted a thriving wine industry in the late 1800s, before an unnamed affliction killed 40,000 acres of the grapevines and put 50 wineries out of business. The problem was later found to have been Pierce’s disease of grapevines. Would Anaheim be wine country today if it weren’t for Pierce’s disease? Probably not, but the sad fate of this Southern California wine industry underscores the importance of controlling the disease and the insects that spread it in California’s thriving grape growing regions.
GWSS has turned out to be a very efficient vector of Xyella fastidiosa, the bacterium that causes Pierce’s disease in grapes. When GWSS made their way to places where scientists believed the bacterium didn’t exist, such as Kern County, grapevines began to express symptoms of the disease. The county agricultural commissioners in the San Joaquin Valley have been working tirelessly over the last 10 years to keep glassy-winged sharpshooters out of grape growing regions to protect a very valuable economic driver. In Fresno County alone, where grapes are the No. 1 agricultural commodity, the crop was worth $961 million in 2011.
Despite the efforts to contain GWSS in Fresno County, the pest is spreading very gradually south and east of the Fresno-Clovis metropolitan area into commercial vineyards and orchards.
“Cooperation by urban residents where we find GWSS has been great,” said Fred Rinder of the Fresno County Agricultural Commissioner’s office. Nevertheless, in 2012, GWSS was found spreading out in Kerman, Parlier, Sanger and Kingsburg.
Stephen Vasquez, UC Cooperative Extension advisor in Fresno County, fears local grape farmers have become complacent about glassy-winged sharpshooter and Pierce’s disease, even though all grapes are susceptible. The best way to control its spread, he said, is to monitor and manage sharpshooter vectors and remove and replace vines that have tested positive for Xylella fastidiosa.
“Be vigilant. Learn the symptoms and train crews and workers,” Vasquez said. “Pierce’s disease has been around for a long time and GWSS has been here more than a decade, but we still haven’t had that marriage of the two. That is potentially devastating.”
The UC IPM website has extension information on glassy-winged sharpshooter and Pierce’s disease.
- Author: Dennis O'Brien
- Editor: Stephen J. Vasquez
When an insect pierces the surface of a plant to feed, much of the action takes place in the plant's interior. A device called the Electrical Penetration Graph (EPG) is a critical tool for peering into the process.
Now a new type of EPG developed by U. S. Department of Agriculture (USDA) entomologists is giving scientists the clearest view yet of the wars waged between piercing-sucking insects and the plants they attack.
The EPG was developed by Elaine Backus at the Agricultural Research Service (ARS) San Joaquin Valley Agricultural Sciences Center, in Parlier, California, and her late partner William Bennett from the University of Missouri.
To use an EPG, researchers connect the insect and plant to an electronic monitor that reads electrical charges produced by changes in voltage that occur as the insect feeds. At least eight different systems have been developed, and researchers who study aphids and other piercing-sucking insects have used them over the years to publish nearly 400 peer-reviewed papers. But the new EPG is much more versatile than any of its predecessors, and is being used by researchers around the country in ways expected to broaden understanding of how plant-feeding insects cause so much damage.
Backus and Bennett described their AC-DC monitor in a 2009 issue of the Journal of Insect Physiology, using it in a series of studies published in the Annals of the Entomological Society of America. These studies focusedon the critical role that saliva plays when the glassy-winged sharpshooter injects the Pierce’s disease bacterium, Xylella fastidiosa, into grapes. Backus believes that the saliva loosens bacteria living in the gut and stylets and carries them into the plant when the mixture is “spit up” during feeding. That inoculation process begins the spread of the disease throughout the plant. Backus could not have gained these insights without the AC-DC monitor.
Traditionally, monitors have been designed to work with either AC or DC current. Because of the physics that govern electricity and the flow of electrical current, researchers have been likely to get best results using AC monitors when studying larger insects and DC monitors when studying smaller insects.
Ideally, a monitor should be capable of studying a variety of insect sizes. As the name implies, the team's AC-DC Monitor incorporates design features from both AC and DC monitors, making it more versatile. Researchers can adjust the settings to the sizes of any insect they are studying. Entomologists will be able to view the feeding process in detail for more insects than ever before. They also will be better able to compare the feeding habits of pathogen-bearing insects with those that are pathogen-free.