Erin Doman on October 7, 2015 24 Comments For winemakers, grapevine diseases can be devastating. Unfortunately, there are many kinds of vine diseases that thrive in all sorts of conditions. Bacteria and fungi cause the most common grapevine diseases. Insects can also spread disease and damage roots. Environmental conditions can trigger fungi development that wreaks havoc on grapevines in vineyards. Below, we have created a list of the 7 most common grapevine diseases that can spoil your favorite would-be wine. 1. Pierce’s Disease (Xylella fastidiosa) The Xylella fastidiosa is spread by the blue-green sharpshooter in California and by sap-feeding insects in Europe. Insects feed on a plant and transmit the bacteria inside the plant, where it travels through the xylem vessels and spreads the infection. Infected vines appear stressed, with leaves turning red or yellow in the summer, berries shriveling, and dead and dried leaves falling off the vine. There is no cure for Pierce’s Disease. However, current research involves using bacteriophages (viruses that kill bacteria) to stop and prevent the spread of Pierce’s Disease on wine grapes. More research is being conducted to learn precisely which bacteriophages can kill the toxic bacteria. A phage cocktail, consisting of four different phages, is used on plants that have already been infected and on plants that have not been infected. The result has been the same so far, that infection is prevented and the existing disease is controlled and not allowed to grow and spread. 2. Phylloxera (Daktulosphaira vitifoliae) Phylloxera are microscopic insects that suck sap and feed on the leaves and roots of grapevines. The roots become deformed and fungal infections occur there, which blocks the flow of nutrients and water to the vine. There is no cure and no chemical control or response available. However, some vine species, such as the American type, have evolved and have natural defenses, such as emanating a sticky sap that repels insects by clogging its mouth as they feed from the vine. Some preventative or curative solutions have involved grafting phylloxera-resistant roots with more susceptible vines. Another innovation being tested is training dogs to smell and detect pests and diseases in the fields. 3. Downy Mildew (Plasmopara viticola) This fungi vine disease can destroy grapes and vine vegetation. Between mid-May and late autumn, the aerial parts of the plant can become infected, particularly when the temperature is below 65°F. The symptoms are oil spots and a moldy cover or bright green spots found on the leaves. A white moldy cover is also found on the shoots and the inflorescences. The infection can also reach the berries, particularly the thriving ones, and cause them to dry out and look like raisins. They may also soften and turn a violet-brown color. Chemical applications, such as fungicides, are used to control the fungus. Also, measures are taken to eliminate humidity and moisture around impacted plants. Drip watering systems and selective pruning to improve air circulation help to do this. Enclosed environments, such as houses or greenhouses, aid in reducing humidity and thus reducing the chance of this mildew from harming the grapevines. 4. Powdery Mildew (Uncinula necator) All aerial parts of the plants can get infected by this disease. Development happens through the entire growing season until late fall. It favors dry years and climates with low humidity and little rainfall. Moldy coats on leaves, inflorescences, and rachis are telltale signs. Berries can become infected in the early stages of their development, with a gray coat covering them and then they dry out afterwards. Infected half-ripe berries usually crack and dry out. The plant’s canes can also become covered with a gray coating with gray-brown spots underneath. To control this pathogen, genetic resistance, chemical methods, and careful farming are used to manage conditions. Fungicides are used as well as silicon, which assists plant cells in fighting against the fungus and strengthening the epidermal cells of the plants. 5. Grey Mold (Botryotinia fuckelina) Fruit crops and aerial parts of vine organs are susceptible to grey mold or botrytis. This disease can strike at any time throughout the year, especially when the temperature ranges between 60 and 75°F. Rainy conditions and overly fertilized vineyards can cause the botrytis to appear. The first signs of the disease are spots on leaves that turn brown and begin to rot. The leaves then die, dry, and fall off the vine. Inflorescences can also rot and dry out. On berries, the most devastating effect of the disease is when the fruit becomes covered with the grey mold and begins decaying. Large-scale field monitoring has been used to test rain shelters to control this and other grape diseases. Rain shelters are more effective than leaving the plants out in an open field. 6. Black Rot (Guignardia bidwellii) All aerial parts of the plant can become infected with this disease. The fungus grows in warm and humid environments between mid-June and late August. The infection likelihood increases when the temperature ranges between 60 and 90°F with a rainy climate. There are first round brown spots on the leaves and the shoots, which die and become dried out. The fungus then reaches the berries while they are still developing. Reddish brown to gray spots appear and then they lose their moisture and shrink into raisins that are brown-black or black-blue in color and have black dots. 7. Vine Trunk Diseases Two grapevine diseases in this category, Petri disease and Esca (black measles), are caused by fungal pathogens. They tend to affect old vines that are at least 10 years old but young vines are not immune. Wood and leaves that have contracted these diseases develop unusual discoloration patterns of stripes or sports. The leaves, and then the stems, eventually shrivel in the middle of growing season and grapes end up falling to the ground. The vine then suffers sudden death, which could happen within days after the initial symptoms appear. The likelihood of these grapevine diseases occurring is highest in dry weather that follows after a wet season. This is a worldwide problem and research is still being conducted on how best to handle the issue. One theory is based on how vines grafted by machine as a cost-cutting and labor-saving measure has created weaker vines than hand-grafted vines. In the meantime, some vintners have tried new pruning techniques to control the fungi spread or splitting vine trunks in half to dry out the fungi and encouraging the sprouting of a new vine branch from below the join. Others inject disinfectants into the trunks. Vine diseases affect vineyards throughout the world. They have devastated plants and ruined crops, causing economical and land distress to wineries. Scientists and winemakers continue their ongoing research and experimentation to keep these diseases under control.
Nelson Barnett says April 2, 2020 at 5:42 pm I lose about half of my crop because they start to rot before they get ripe what can I do to take care of this problem Reply
debbie waddell says May 24, 2016 at 3:09 pm Had two plants that started out with small misshaped leaves and very obvious to spot when looking at a row of vines. Now those two have become over half of my chardonnay and now noticing this on other varietals. I searched and thought it was eutypa dieback. Have sent one plant to OSU in Oklahoma for diagnosis. Any ideas? Reply
Bryan Rowsey says March 14, 2017 at 7:00 am I bought my rasbery, blackberry, blueberries, two of each at home depot, a majority of the leaves are turning yellow ,it was very cold the morning we bought them I’m assuming that they bring them in at night ,is it the lack of sunlight, it’s 15%outside and can’t put them out yet any help would be a help Reply
frank says September 1, 2018 at 3:32 pm this is adated reply but it may help alot plants turn yellow for lack of water dont let it dry out even in winter too much water will cause yellowing also Reply
Gary Kendall says April 27, 2017 at 2:26 pm All 3 of my vines the grapes mature in size but they all rot before they ripen. Reply
frank says September 1, 2018 at 3:27 pm this info is 1and1/2 yrs late but captan will stop that problem prune good in late winter start spray early feb to late march about 2weeks apart Reply
dennis weston says May 15, 2017 at 2:02 pm My 2 year old vine has small brown blisters along the main wooden stem,the plant appears healthy but the blisters secrete a sticky fluid, I have sprayed with an insecticide,and tried to pick them off, but I am worried as there does not seem to be any info anywhere on this phenomenon. Reply
Sarah Frisch says July 20, 2017 at 5:15 pm Hi, my grapes are loaded, most still green, the ones that are turning purple are shrinking and shriveled. There doesn’t seem to be anything affecting the leaves or vines. Would love to attach a picture. Wondering if there is a fungicide I need to apply or what. Thanks Reply
don says October 15, 2017 at 8:57 pm I am in NSW Australia,have a young grapevine growing well now coming into spring and summer.Have noticed the ieaves developing a black spot and spreading all over the leaves and then dies.How can I treat this problem? Reply
Lori Schmidt says April 17, 2018 at 8:49 pm we have 2 concord grape vines. I prune them in mid winter and they grow beautifully and also produce a good number of grapes. However, most of the grapes are small and most of them are attacked by an insect that leaves a small hole in each grape and often some of the grapes are surrounded by a web. What is the problem and what can I do? Reply
Mrs. Lemaire says January 31, 2019 at 2:55 am Okay, This will sound super crazy, but your “About Author” widget is also me……. if you are not me in an alternate universe, you are my guru! We are out there and we hear you. Thank you for your article! Kindest Regards, Mrs. LemaireRVA Reply
Wm. B. Redington says February 16, 2019 at 5:44 pm the past 3 years my grapes form to nice bunches ,rely good looking .then they start to dry and shrink up .can you help me with some imfo. to help thank you Wm B.Redington Reply
Gabe says May 16, 2019 at 5:04 pm I live in Virginia just outside of Washington DC and I have about 20 grapevines. About half of them were planted last year and they have developed very well a couple months ago going through the first pruning. Three or four weeks ago one of the plants started losing consistency and you could tell that he is slowly dying. There are no signs of bugs or fungus or anything else just the plants slowly dying. In the last few days I’ve noticed a second vine right next to the first one I mention that is now started fading and I’m afraid that he’s going to die as well The vines are planted in a sloped area well drained and have sun most of the day I checked the soil near the first plant that was affected and couldn’t find anything that was obviously attacking or damaging the plant Any hints or advice would be appreciated Many thanks Reply
Deborah Engle says May 22, 2019 at 10:17 am bought a house in Oct., and have 2 mature grape vines that never received much care, so we pruned them last fall, then just fertilized them and have been watering regularly. Some of the leaves (mainly the newer leaves) have developed a thin, white coating and I don’t know what is is,or how to treat it. If the sun comes out today, I’m going to try a mixture of 1 part whole milk and 9 parts water to spray on them, that I read about on line (It’s also supposed to be good for all types of vine-plants, so I’ll try using it as a preventative measure on my vegie garden. Reply
Jlo says June 15, 2020 at 1:08 pm Did it work? The 1 part whole milk with 9 parts water? This is the first time that mine have powdery mildew:( Reply
Alice Dalby says September 9, 2019 at 2:53 pm I have red shoots coming off the trunk of my vine. Can anybody tell me what this is Reply
Pat Jordan says February 9, 2020 at 1:55 pm I just trimmed my vines and found 3 wines with an odd collection of hard oval shaped matter/bugs? They don’t move or look like bugs but it’s something weird. They are in rows altogether on stems & so far I only see it on 3 vines in one place each vine. I cut them off and now need to know what to do to avoid more vines getting them. When I smashed one of the oval shapes, it was liquid inside. They cling to the stem in rows. Anybody know what this could be? Reply
Pat Jordan says February 9, 2020 at 4:16 pm meant to say 3 vines with the oval hard-shelled bugs Reply
Srinivas says June 1, 2020 at 2:17 pm It will be great to show the pictures along with disease. Currently the leaves of my grapevine are turning yellow really fast. Most of them are happening under the canopy. I applied iron and zinc and it has no impact. I see no insects. Now it can be either nitrogen deficiency or some root disease. How will I know? Reply
Lana Lanham says June 7, 2020 at 8:00 am My grapes have a lot on the vines but some of the grapes seem to have popped open and now look fuzzy. What is happening? Reply
Mr Anthony Allsopp says July 22, 2020 at 2:45 am Hello I live in the Uk and I have two grapevines that we purchased so ten or so years ago. One red and one white the white grape has always been the stronger of the two vines.They are planted about 9 foot apart on a south-facing small slope in a warm/hot outdoor climate depending on Uk weather. They are trained up the side of a wall on a Tressel The problem is with the Red vine this year It has no new growth and very few leaves. The few that are there look like autum folage red around the edges ready to fall. An of course there are no grapes at all. If this is a diesiese what can I do to treat it or do I need a new vine ?? the White vine go’s from strength to strength with buches of wonderful fruit. Kind regards Anth Reply
Sue Mcgowan says October 5, 2020 at 6:11 pm Hi I have a Walter cross grape growing in my Greenhouse which gets great cross ventilation. The vine has fantastic growth with very healthy green leaves and new bud growth however the vines are very flimsy, when I touch them they fall off the main stem. This morning I found 2 that were 30 cm or longer on the ground. Last year was its first year of fruiting so this year is its 3rd year. The plant looks very healthy. Reply
