Grape vine diseases are serious threats to vineyards and homegrown grapes all over the world, and could be devastating to your plant, its fruit production, and winemaking. Not only is it heartbreaking to lose a plant you’ve been nurturing for however much time you’ve had it, but grape vine diseases can also impact small economies that depend on grape production for a variety of different products. Most grape vine diseases can be blamed on bacteria, fungi, and viruses, which spread easily through pest damage.
Keep reading to learn about common grape vine diseases, and how to treat them.
Fungal, Bacterial, and Viral Diseases
Before we get to talking about specific grape vine diseases, let’s talk about different kinds of diseases.
- Fungal Grape Vine Diseases: fungal diseases are the most common grape vine diseases, and luckily, the easiest to manage, as well. Fungal spores often hide out in old organic material and usually impact foliage with surface-level symptoms, but sometimes go deeper into the plant tissue, as well.
- Bacterial Grape Vine Diseases: bacterial diseases are unfortunately much more serious than fungal diseases. Depending on the type of disease and severity, they can destroy crops because of how contagious they are. Some are very difficult to get rid of because the disease gets into the soil and can impact plants planted in the same location after the diseased one has been gotten rid of. The good news for home gardeners (but not for the grape industry as a whole) is that bacterial diseases are more common in large grape cultivations.
- Viral Grape Vine Diseases: the 86 known viral diseases in grape vines worldwide can range widely in different levels of severity. Viruses are tricky because symptoms depend on the grape variety and weather conditions, along with the fact that some grape vines are simply asymptomatic even in the presence of a virus. Viral grape vine diseases can pass between vines through pests, or the use of previously infected plant materials or tools. Tests exist to ensure that plant material is virus-free.
5 Common Grape Vine Diseases
1 Grapevine Leafroll Disease
Grapevine Leafromm Disease (GLD) is one of the most common grape vine diseases out there.
The damage caused by the disease depends on the grape vine variety, the weather, the soil, and the cultivating practices. Additionally (and much like viruses in humans) symptoms are inconsistent, and usually only emerge during or after the grapes have ripened: this makes diagnosing the disease simply by analyzing the symptoms practically impossible without a test.
Some of the most widespread symptoms include late blooming, smaller growth, discoloration in the foliage, less fruit production, curling leaves (in very advanced stages) and sometimes poor-tasting grapes because of a disrupted balance between acidity and sugar.
The discoloration makes it so that the symptoms are more easily recognizable in dark grape varieties, and remain less noticeable in lighter varieties.
Prevention is the best cure for Grapevine Leafroll Disease, because there is no cure. That means disinfecting your tools between uses, and only buying disease-free vines from nurseries.
2 Pierce’s Disease
Pierce’s Disease is an infectious disease that causes grape vine leaves to turn reddish or yellowish during the warmer months and ultimately shrivel and die, in addition to the grape vine fruits themselves drying up and becoming inedible.
The infection is caused by bacteria carried by insects that contaminate the plant when they feed on its sap. The bacteria then spreads through the plant’s xylem vessels
Unfortunately, there is no cure for this infectious disease, but scientists are hard at work researching how bacteriophages can curb its symptoms and spread within grape vines. Additionally, you can also use pesticides to try and keep the sap-eating pests that infect the grape vines away.
3 Red Blotch Disease
Red Blotch Disease has been identified relatively recently, which means that experts aren’t sure yet of the extent to which the disease has damaged the grape economy, even though it has now been identified throughout the United States. The disease was probably spread through the use of infected tools and organic material before experts had been able to document this new disease.
The disease is called Red Blotch Disease because the diagnosable symptoms include the appearance of red spots on certain leaf blades. Unfortunately, Red Blotch Disease is similar to Grapevine Leafroll Disease in its widespread symptoms once the disease is advanced. Leaves tend to curl downwards, fruit production decreases, discoloration appears, and grapes taste sour and are shriveled. Additionally, symptoms are more easily spotted on dark grape varieties than on light grape varieties. Unlike Grapevine Leafroll Disease, however, the discoloration in Red Blotch Disease also turns veins reddish.
Because the disease has been identified so recently, experts still don’t know what the long-term effects will be. That means that there is also no known cure: the best course of action is to always make sure you are planting certified disease-free plants!
4 Rugose Wood Disease Complex
Rugose Wood Disease Complex is a complicated disease caused by different viruses that display a wide variety of symptoms that mostly impact the vine itself (as opposed to the foliage). Sometimes bugs might be carriers of one of these viruses.
These include pits and grooves in the vine beneath the bark, near a graft union; the swelling of the scion (the plant part that you graft onto a rootstock during grafting processes); the roughening of the bark around the same area, and more. As far as the foliage goes, it might seem overall less healthy, display late blooming, and will eventually die.
As you might start to expect, there is no cure to the Rugose Wood Disease Complex. That means that prevention by ensuring that you are only working with healthy, certified disease-free rootstocks and scions is more important than ever.
5 Downy Mildew
Downy Mildew is a very serious fungal disease that causes the widespread devastation of grape vines and manifests as yellow lesions on any green part of the plant. At an advanced stage of the disease, you may also find a white powdery substance on the underside of the foliage. The fruit will shrivel, take on a gray color, and eventually drop off the plant, while shoot tips thicken, change shape, and then darken and die.
This fungus hangs out in dry leaf piles during the winter, and its spores are then carried by water and rain to infect the surrounding plants in the spring, especially between mid-May and the fall.
As usual, the best cure is prevention. That includes moisture control (like making sure that the soil is draining well), raking away dead leaves that might accumulate during the winter, pruning, and applying fungicides.
Products for Preventing Grape Vine Diseases
As I’ve mentioned several times now, unfortunately most grape vine diseases have no cure, and few’s symptoms can actually be managed. Most times the only course of action is to remove and destroy the diseased plants, and then start over. That means that you should always make sure that the organic material you are purchasing is certified disease-free, so you at least know that you are starting out with healthy plants.
Additionally, you can also consider the following product that will help avoid cross-contamination and maintain your grape vine’s overall health:
- A disinfectant cleaner for your gardening tools
- A garden rake to keep the earth around your grape vines clear
- An organic fungicide to help prevent fungal diseases
Wrapping Up Grape Vine Diseases
If this post has inspired you to do one thing, I hope it’s this: to buy certified disease-free plants, scions, and rootstock from a trusted nursery. If you don’t, you risk spreading the grape vine diseases above, which severely impact the health of your grape vines and grape production. Remember that prevention is key!
Excited for more grape content? Next, check out my grape vine page for more growing tips, care guides, recipes, and more!
- About the Author
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Margherita Bassi is a freelance writer, journalist, and editor. She grew up between the US and Europe, and nurtured her love for nature and the outdoors in both countries.
In the US, she went on dozens of RV trips with her family, scouted out the best restaurants in every city she visited, and learned how to grow herbs and veggies of all kinds by watching her mother.
In Europe, she experimented with gardening in small spaces, like the small balcony of her apartment in France. With an MA in International New Media Journalism, Margherita is also a skilled researcher in a wide range of topics, and has extensive experience interviewing both individuals and experts.