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Category: Grapes

  • Grape Sustainability at Risk With Pierce’s Disease

    A tour of the research vineyard at the Clanton Research and Extension Center in Chilton County at the Alabama WIneries and Grape Growers Association meeting in September 2019. Grapes are grown by Elina Coneva and the staff at the CREC. Grape varieties are developed by Dr. Andy Walker, a grape breeder at UC Davis.

    Pierce’s Disease is wreaking havoc in grape vineyards in the Southeast. It is such a problem that University of Georgia Cooperative Extension plant pathologist Phil Brannen is concerned about the sustainability of some farming operations, especially as winter temperatures continue to get warmer.

    “Once you get above 2,000 feet in elevation, I have only rarely seen a single plant come down with this (disease) and that’s still the case. But the areas that are around 1,700 feet in elevation where we used to not see that much of it, when we have two or three warm winters in a row, we really start to see a lot of it. Some of those vineyards, they’re losing 400 to 500 vines a year. That’s not sustainable,” Brannen said. “A lot of vineyards right now that are in north Georgia, they’re suffering a lot of loss from Pierce’s Disease now. If the temperatures get continuously warmer in the wintertime, I don’t know where we’re going to grow this grape.”

    What is Pierce’s Disease?

    Pierce’s Disease is caused by a bacterium that is transmitted by numerous sharpshooter insects, such as the glassy-winged sharpshooters. The bacterium clogs the grape xylem and cuts off nutrient and water flow to the vines. Once infected with Pierce’s disease, vines will die within one to two years.

    “You’ve got the xylem that carries that water and nutrients and if it’s clogged a little bit, you may get by if you have plenty of moisture, but if you get less and less of it, then the water will collapse in that vessel and then you don’t get any,” Brannen said. “When it’s real dry conditions, that is when the symptoms really start to show up. It’s a scorch around the leaf is what you’ll initially see. The berries actually dry up. They form raisins on the vine. You’ll see all of that occurring when it gets really dry in late summer.”

    Brannen said right now is when grape producers will start seeing Pierce’s Disease symptoms.

    Most Effective Management Tactic

    He said the best management tactic that growers potentially have is with disease resistant plants, bred by scientists at UC Davis and are being researched at a couple of sites in Georgia and in Alabama.

    According to Elina Coneva, an Extension specialist in the Horticulture Department at Auburn University, three red wine grape selections were planted at the Chilton Research and Extension Center (CREC) in Clanton in 2010 and are showing promising results. One white wine selection was planted in 2017. So far, the research team has not lost one plant to Pierce’s Disease.  

    The only other option is try to apply a soil-based Imidacloprid insecticide in the spring to kill the sharpshooter insects.

    “If it goes into the root system and gets into the soil, it will last a long time in the plant. That will kill the sharpshooters and that cuts back on transmission a lot,” Brannen said.

  • Grape Root Borers Detected in North Georgia

    Grape root borer.

    According to the UGA Extension Viticulture Blog, the grape root borer adults have been detected in north Georgia. Brett Blaauw, University of Georgia assistant professor in the Department of Entomology, confirmed that on Monday, they collected some adults in their pheromone traps in Lumpkin County, Georgia.

    Adults have started to emerge from the soil, and for the next few weeks, the adults will mate, and the females will lay eggs at the base of vines. Producers with a history of grape root borer in their vineyards need to start monitoring for the pest and initiate management if necessary.

    As the name implies, the grape root borer larvae feed on the roots. Blaauw said they have a two-year life cycle and will feed underground on the roots for almost 22 months. Unfortunately, it is out of sight, out of mind for many grape producers. Being underground, the borers go unnoticed until the vine begins to deteriorate.

    In terms of management, since the adults are now emerging, it is too late in the season to apply dispensers for mating disruption. Chemical management is our key option. Currently, the only insecticide registered for control of grape root borer is Lorsban 4E (chlorpyrifos), which is applied as a coarse spray to the base of vines to kill adults as they exit the soil and newly hatched larvae before they attack the vine. However, Lorsban should not be made within 35 days of harvest.

    The first signs of infestation are yellowing and wilting of leaves with loss of plant vigor and reduced production. This will lead to reduced shoot growth over time, including smaller leaves and berries, loss of vigor and reduced yields.

  • SWD Management Key for Grape Producers

    By Clint Thompson

    In his UGA Extension blog, Brett Blaauw, Assistant Professor in the University of Georgia Department of Entomology, alerted grape farmers that management for spotted wing drosophila (SWD) is approaching soon.

    Brett Blaauw

    SWD flies are active year-round but near veraison, as the brix levels in wine grapes reach 15 degrees Brix, the grapes become attractive and susceptible to SWD. SWD and other drosophila flies can spread and exacerbate sour rot.

    Management is key. Proper sanitation of the vineyard can reduce populations. If farmers harvest grapes frequently and remove fallen or unmarketable fruit, it will prevent the buildup of ripe or rotting fruit. This reduces sour rot inoculum and potential breeding areas for the flies.

    Insecticides are effective at killing adult flies and are recommended if you have a history of SWD in your vineyard or have prior issues with sour rot. Insecticide treatments should begin when grapes are near 15 degrees brix. Treatments should be applied at least every seven to 10 days. Rotating insecticides with different modes of action is very important.

    Make sure to read the label and check the pre-harvest intervals before applying any chemical.

    Note that the combination of an insecticide and Oxidate 2.0 significantly reduced SWD and sour rot prevalence in treated plots.

    If you are unsure whether SWD is a problem at your vineyard, it is easy to monitor for the flies. Traps can be made from plastic cups with lids.

    As always, management recommendations can be found at: https://smallfruits.org/files/2019/06/BunchGrapeSprayGuide.pdf.

  • Pierce’s Disease Training

    UGA photo/Jordan Burbage, of the UGA Soil, Plant and Water Analysis Laboratory in Athens, Georgia, harvests grapes at Trillium Vineyards, part of the collaborative research project being conducted by UGA Extension and Westover Vineyard Consulting.

    By Clint Thompson

    In his latest UGA Extension Viticulture blog, University of Georgia Extension Fruit Disease Specialist Phil Brannen says grape producers will soon be seeing symptoms of Pierce’s disease in susceptible varieties; typically Vitis vinifera and some hybrids.

    Mild winter temperatures have contributed to an increase in Pierce’s disease at higher elevations in Georgia and throughout the Southeast. Symptoms normally start to appear in late July or August. Since symptoms are similar to drought or nutrient stress, it’s essential not to remove plants if they’re not suffering from Pierce’s Disease.

    N.C. State hosted an effective workshop about Pierce’s Disease that will be helpful for all farmers.   

    Brannen stresses it is particularly important that you identify and destroy infected vines to prevent further spread of this disease.

    The disease is caused by a bacterium that is transmitted by numerous sharpshooter insects, such as the glassy-winged sharpshooter. It clogs the grape xylem, cutting off nutrient and water flow. Once infected with Pierce’s disease, vines die within one to two years.

  • Root Borers a Danger to Grapes in the Southeast

    University of Georgia Extension/Pictured is a grape root borer.

    By Clint Thompson

    The time is now for grape producers to protect their crop against the grape root borer, said Brett Blaauw, assistant professor in the Department of Entomology at the University of Georgia. He said usually in north Georgia, the grape root borers will emerge in early July.

    According to the UGA Extension Viticulture Blog, if farmers have not deployed their pheromone dispensers as part of the mating disruption tactic, it is time to get those distributed.

    University of Georgia Extension/Pictured is a grape root borer monitoring trap.

    “Our mating disruption is probably our best option. That’s using a pheromone that basically confuses the male moths. It blocks them from finding the female moths so they can’t mate. No mating, no mates, no eggs, no larvae and then, hopefully, no disruption of the roots,” Blaauw said. “But because of its two-year life cycle, it takes a least two years for the mating disruption to start to show that it’s working in a vineyard. That can be tough because when you use something management you want to see it working right away. But the main disruption takes a couple of years to see any benefit.”

    What Impact Does Grape Root Borers Have?

    As the name implies, the grape root borer larvae feed on the roots. Blaauw said they have a two-year life cycle and will feed underground on the roots for almost 22 months. Unfortunately, it is out of sight, out of mind for many grape producers. Being underground, the borers go unnoticed until the vine begins to deteriorate.

    “Previous research has shown that by having these larvae feeding on the roots it can reduce the vine’s yields by 50%. That’s just having one larvae,” Blaauw said. “The mature larvae are almost an inch long so they’re pretty good size larvae, a little bit like root boring caterpillars feeding for two years. Just having one can reduce yield by 50%. If you have more than one feeding on a vine, that could easily significantly reduce the survivability of the vine; it can reduce the fruit quality and eventually lead to vine death.

    “Growing fruit in the Southeast is tough enough with diseases and other insects. Growing grapes is really tough. Grape vines, at least the vonifera type grapes are often subject to different diseases. One is Pierce’s Disease. Pierce’s Disease can take down vines pretty quickly, too. A lot of growers, when they have a vine that dies, they kind of assume it’s due to a disease. They’re not usually thinking about grape root borer just because it’s underground. You don’t really see what’s going on until you pull that vine out and see the roots all chewed up. Then it’s obviously too late.”

    Effective Management Tool

    Another effective way to manage grape root borers is to suppress the weeds under the vines. This can significantly reduce the success rate of the eggs hatching and the larvae making it to the roots. If weeds are present, they serve as protective barriers for the little caterpillars. They protect them from the sun and protect them from other insects that are going to be feeding on them.

    “If you get rid of those weeds, you create a pretty harsh environment. Bare soil is not a good place for an insect, especially if you’re a tiny little caterpillar,” Blaauw said.

  • Grape Producers Need to be Wary of Downy Mildew Disease

    University of Georgia photo/Shows presence of downy mildew disease.

    By Clint Thompson

    Grape producers in north Alabama and north Georgia need to be wary of downy mildew disease. It has been confirmed in vonifera grapes in two separate Georgia locations, says Phil Brannen, University of Georgia Cooperative Extension fruit disease specialist.

    “My hope is that if folks are spraying well, if they’re actually effective in spraying the vines and keeping fungicides on the vines, hopefully they won’t see this,” Brannen said.

    Phil Brannen

    He said initial symptoms of downy mildew are “oil” spots on the upper leaf surface with white, fluffy spore formation on the underside of the leaf. The important factor for grape producers to consider is protecting your leaves. As Brannen often preaches to his students at UGA, “plants don’t do well without leaves.”

    “What we more often see with downy mildew on grapes and the susceptible varieties is that it will actually infect the leaves and you’ll get so much infection potentially if you don’t get enough fungicide out in a timely fashion, you could actually lose your leaves,” Brannen said. “If you lose your leaves, even though you have grapes that look fine … you cannot mature a grape for wine in that way. You’re going to have a real bad wine that would come from those grapes. You don’t want that to happen.”

    First Discovered

    Brannen said he first discovered downy mildew in a vineyard in west Georgia. But last week it showed up in his research plots in Watkinsville, Georgia.

    “The secondary thing is if you lose enough leaves then you don’t store enough carbohydrates to the root system to survive the winter and you’ll have winter damage.”

    Brannen cautions growers who are scouting for downy mildew to not confuse it with powdery mildew symptoms. In his Extension blog, Brannen said, “If you falsely identify downy mildew as powdery mildew, you are likely to start an aggressive spray program for powdery mildew that just allows the downy mildew to only get worse.”

    Brannen provides a video on how to properly identify the presence of downy mildew.

    He recommends incorporating highly efficacious materials such as Zampro, Revus, Ridomil Gold MZ (note the pre-harvest interval), etc. in spray programs moving forward.

    Rain Contributes to Disease

    The wet conditions have only fueled downy mildew’s fire in recent weeks.

    “We’re getting a tremendous amount of rain in the last week or two. It seems like it rains every couple of days, if not every day. A lot of pop-up thunderstorms. That wets the leaves. The morning dews have been really wet. We tried to spray on Monday, went up to Blairsville (Georgia) to spray and we were just covered up in wetness,” Brannen said.

  • May Frost Sours North Carolina Grape Production

    By Clint Thompson

    A May frost appears to have soured North Carolina’s grape production this year, says Mark Hoffmann, N.C. State small fruits Extension specialist.

    Hoffmann

    “The western part of the Piedmont region, they got hit pretty bad. We have some areas where we have 100% loss,” Hoffmann said. “The Yadkin Valley got hit pretty bad, and everything west of that, really.”

    The devastating impact to the state’s grape production is isolated to vonifera grapes. The area where the frost did the most damage produces about 80% of the state’s production. Fortunately, the state produced a bumper crop last year.

    “We had a very good year last year and the tanks are full. It’s not going to be like as traumatic as it would be if we would have two or three bad years in a row,” Hoffmann said.

    Hoffmann confirmed in an earlier interview this was the third frost event for the state’s grape crop. It was especially vulnerable this time since it happened late in the season.

    Fortunately, he said muscadines that are grown in the Southeast area were spared.

  • Powdery Mildew Alert!

    Photo by Phil Brannen-UGA/Shows powdery mildew disease.

    According to UGA Extension Viticulture blog, University of Georgia Cooperative Extension Fruit Disease Specialist Phil Brannen says powdery mildew is just starting to show up on untreated plants in the research grape vineyard at Blairsville, Georgia.

    “I hope you will not see it yet in well managed vineyards, but recent rains and other difficulties may have hampered spray programs,” Brannen said.

    Spray programs need to be applied on a 7-to-10 day interval when rain events occur as often as they are. Growers also need to use the more efficacious materials at critical infection periods such as bloom and early cover sprays.

    It’s important to scout your vineyards and make sure to contact your local county agent should you have questions concerning this disease or others. The 2020 Southeast Regional Bunch Grape Integrated Management Guide can be found at small fruits. It contains valuable information related to the timing and efficacy of fungicides for powdery mildew.

  • Japanese Beetles Active in Georgia Vineyards

    Photo by University of Georgia/Shows Japanese beetle.

    According to the UGA Extension Viticulture Blog, Japanese beetles are starting to become more widespread in west Georgia vineyards. University of Georgia entomologist Brett Blaauw says the pests are only beginning to emerge but expects the populations to increase exponentially over the next few weeks.

    “In large enough numbers, Japanese beetles can be a severe pest of grapes during the summer, feeding mainly on foliage and (thankfully) rarely on the berries,” Blaauw said. “More problematic is Japanese beetles feeding on new plantings. Older, established vines can withstand some feeding damage, but young vines can quickly become defoliated from these beetles. Special attention should be given to newly-planted vineyards.”

    As temperatures continue to heat up as we progress throughout the summer, this is ideal weather conditions for beetles to be active. They love warm, sunny days and congregate in groups on vines to feed and mate near the top of the canopy.

    There are no thresholds for Japanese beetle leaf damage. However, management is required when feeding damage is below the top trellis wire or about 15% of the leaves are damaged.

    “Growers should rely on their judgment and experience to determine whether beetle abundance and/or injury warrants chemical control,” Blaauw said.

    For more information, see UGA Extension Viticulture Blog.

  • UGA’s Releases New Muscadine Variety ‘RubyCrisp’

    By Sadie Lackey for UGA CAES News

    From late summer into fall, Southerners start looking for muscadines – a popular grape native to the southeastern United States. Selections run from the dark purple, thick-skinned traditional muscadine to a light golden-green variety. Growers and consumers can soon add a new red variety to the mix.

    UGA photo/UGA researchers released a new red ‘RubyCrisp’ muscadine variety for those who want a sweet berry flavor with just a hint of muscadine.

    The University of Georgia College of Agricultural and Environmental Sciences’ muscadine grape team, led by horticulture professor Patrick J. Conner, developed a variety of muscadine for those who prefer the sweet taste of a berry with limited muscadine flavor.

    “The unusual red color of this berry really makes it stand out,” Conner said. “But the tender skin and crisp flesh of this variety are what truly make it unique. The texture of this variety is a marked change from traditional muscadines, which are often known for having tough skins and a soft pulp.” 

    ‘RubyCrisp’ Background

    Researchers found ‘RubyCrisp’ to be a good fit for pick-your-own operations and home gardens because of its distinctive taste and texture and excellent productivity. Unfortunately, commercial production is not a good fit for this specialized berry, because it often cracks with rough handling. However, ‘RubyCrisp’ vines can flourish in the backyards of at-home cultivators looking to try the newest muscadine.

    ‘RubyCrisp’ originated in Tifton, Georgia, as a result of a cross between ‘Supreme’ and ‘Tara’ varieties. ‘Supreme’ produces black berries with exceptional size and firmness. ‘Tara’ produces bronze berries with dry pedicel scars that ripen early in the muscadine harvest season. In 2011 the ‘RubyCrisp’ vine was chosen because of its large berry size, flower type and outstanding flavor.

    The original ‘RubyCrisp’ vines were tested on UGA experiment plots in Tifton and at a commercial vineyard in Wray, Georgia. Researchers discovered there that given the large berry size and high production potential of ‘Ruby-Crisp,’ growers may need to limit vine fruitfulness by increasing the distance between fruiting spurs or thinning the crop so that the vine is not weakened by maturing excessive crops. 

    UGA researchers also found that heavy rainfall can lead to fruit cracking. ‘RubyCrisp’ has a mid-season harvest date around Aug. 21 in south Georgia and has perfect flowers so it does not need a pollinator.

    “Because further study is needed to explore the optimum environment for producing this vine, especially its cold hardiness, we suggest growers in northern muscadine regions refrain from planting large numbers of ‘RubyCrisp’ until more data is collected,” Conner said.

    UGA’s Established Muscadine Breeding Program

    UGA has the oldest muscadine breeding program in the United States. The program began in 1909, and since then, has released over 30 cultivars and counting. The program focuses on continued improvement of the muscadine grape by developing new cultivars that satisfy the needs of growers and the demands on consumers. The UGA muscadine breeding program works to create new cultivars that combine large berry size with perfect flowers, expand the harvest season with earlier and later ripening dates, and produce berries with dry stem scars, crisp flesh and tender skins.

    A list of nurseries licensed to propagate ‘RubyCrisp’ muscadine is available by contacting Conner at pconner@uga.edu. For more information about the UGA muscadines.