Important Plant Health Issues to Take into Consideration
By: Judit Monis, Ph.D. – Vineyard and Plant Health Consultant
As many of you already know, I am a plant pathologist consultant specializing in the detection and control of grapevine diseases. The diseases work with are those that are graft transmitted but are also can spread in the vineyard. Once the vines are planted, these diseases cannot be cured using chemical or other means. It has happened too many times that I am called to determine what is wrong at a vineyard. The story goes sometimes like this, “we purchased the vineyard in the winter, so we were unable to see any tell-tale signs of disease”, “we consulted with our county officer and s/he said things looked OK”; We really were not thinking about disease, we fell in love with the beautiful setting and the house”; “We did not know that red foliage is an indicator of virus infection”; the scenery in the fall season is an explosion of colors, so beautiful, so romantic”. I can go on and on with more quotes buttthink that you understand the problem. I wish these people would have called me before they purchased the vineyard. Now it is a bit late.
In this article, I will highlight issues that can become a problem after a vineyard purchase. It is my hope to educate the reader and encourage them to contact me prior to signing the purchase contract to allow a thorough evaluation of the vineyard health status.
The Best Time to Inspect a Vineyard for Disease Presence
As mentioned earlier I will only focus on graft transmitted diseases that cannot be cured once established in a vineyard. Diseased grapevine plants may display different symptoms of infection at different times of the year or seasons. Early in the spring and summer months it is easy to spot diseases caused by declining bacteria (i.e., Pierce’s disease, crown gall), fungi (Eutypa and Bot canker, black foot, etc.), and viruses (fanleaf and other nematode transmitted virus species). In late summer or fall, viral diseases that cause leaf reddening and a variety of color schemes (leafroll, red blotch, Vitiviruses) can be observed. To complicate matters, these diseases or their disease-causing agents can be found in all sorts of combinations. Further, some of these diseases show almost exactly the same symptoms, in all cases a knowledgeable plant pathologist will be required to help identify the issue or recommend testing, especially when no symptoms are present due to seasonality.
Below I describe some of the most important diseases likely present in vineyards:
Bacterial, Fungal and Viral Pathogens Best Detected in the Spring
Petri Disease, Young Vine Decline, Esca: The disease in young vines, known as young vine decline, is caused by Cadophora, Phaeoacremonium, and Phaeomoniella species. In older vines, the same fungal pathogens are associated with Esca disease. The disease is chronic when vines express a gradual decline of symptoms over time, or acute when the vines decline and die within a few days. These acute symptoms are known as the apoplectic stage of the disease. It is not uncommon during the apoplectic stage of the disease to see dead vines carrying mummified grape bunches.
Canker Diseases: Various pathogens can cause canker symptoms, large discolored areas in trunk and canes, in the vineyard. Bot-canker or dead arm disease is caused by different species in the Botryosphaeriaceae family. Eutypa dieback is caused by different species in the Diatrypaceae family. In my lab we characterized Seimatosporium species as a fungal pathogen that causes decline and cankers in grapevines, but within the same fungal group others have reported Pestalotoipsis and Truncatella to cause disease in grapevines. The canker symptoms observed in the sections of affected cordons or trunks in grapevines may appear to be similar but caused by unrelated fungal species.
Black Foot Disease: Species of Campylocarpon, Cylindrocladiella, Dactylonectria, and Ilyonectria (previously known as Cylindrocarpon spp.) are the causal agents of this complex disease. These fungi are soil-born and most active on compact soils with poor drainage. Symptoms above ground can be indistinguishable from young vine/ Esca disease described above. Additionally, the decline symptoms can be confused with Pierce’s disease (to be described below).
Grapevine Fanleaf and Other Nepoviruses
Arabis mosaic (ArMV), Grapevine fanleaf (GFLV), Tobacco (TRSV) and Tomato ringspot (ToRSV) are viruses that cause decline in grapevine. These are specifically transmitted in the vineyard by different nematodes in the Xiphinema species. The symptoms caused by these viruses are very similar and include foliar deformation, vein banding, and most importantly uneven maturation and sparce production of berries. Since this is a soilborne disease, it manifests in patches in the vineyard where the nematode vector is located. The transmission, of course can happen through infected material, but not commonly as it is an easy virus to detect using various laboratory techniques.
Pathogens Best Detected in the Late Summer and Fall
Pierce’s and Crown Gall Disease: Pierce’s disease is caused by Xylella fastidiosa, a bacteria transmitted by sharpshooter sucking insects. The control of the disease is complicated as the bacteria infects many different plant species (i.e., has a broad host range). The symptoms observed in early spring are vine decline and poor bud break, in the fall it is possible to observe typical “green islands” on the canes as well as the “match stick” symptoms. Green islands are areas of the canes that do not mature evenly (uneven lignification), while match stick symptoms is a phenomenon in which the petioles remain attached to the canes while the leaf blade has fallen off. Crown gall is caused by another bacteria: Agrobacterium vitis. The typical symptoms of crown gall disease are galling at the crown of the vine (hence its name), however galls can occur at the graft union or other areas of the vine. I have recently written about crown gall disease in grapevine and will not elaborate on this article.
Fungal Pathogens and Mixed Infections: The fungal pathogens and the crown gall bacteria mentioned above can be detected all year round and often occur in mixed infections with viruses and/or bacteria. Some years ago, Central Valley growers in California reported a syndrome in which their vines collapse and die within a short period of time. While working at STA (the laboratory I developed that specialized in grapevine diagnostics) we tested vines with similar symptoms, not just from California’s Central Valley but also from California’s Central Coast vineyards. We detected a combination of fungal pathogens (not always the same usual suspects) and viruses, such as Grapevine leafroll associated -3 (GLRaV-3) and the Vitiviruses Grapevine virus A and F.
Grapevine Leafroll and Red Blotch: Although the symptoms observed in vines infected with Grapevine leafroll and red blotch viruses are similar, these diseases are caused by different viral species. The symptoms are observed in the late summer and fall and appear as a display of a palette of different colors. Some species of leafroll are transmitted non-specifically by mealybugs while red blotch virus was reported to be transmitted by plant hoppers in the Membracidae family, In the next Grapevine Magazine issue I plan to write an article with more details on epidemiology and management of these diseases. Stay tuned!
Conclusions
The purchase of a vineyard is a huge investment and because of this It is important to take into consideration its plant health prior to purchase. Because symptoms of disease vary along the different seasons, I recommend planning to test a representative sample for important diseases during the due diligence period. Be aware that certain viruses/pathogens are detected more readily in different seasons. This is why it is so important to hire a knowledgeable professional that can walk you through the process.
My philosophy is always prevention, so my recommendation to buyers as well as sellers is to be aware of the infection status of planting material, this will avoid the presence of detrimental pathogens in the vineyard in the first place.
Judit Monis, Ph.D. provides specialized services to help growers, vineyard managers, and nursery personnel avoid the propagation and transmission of diseases caused by bacteria, fungi, and viruses in their vineyard blocks. Judit (based in California) is also fluent in Spanish is available to consult in all wine grape growing regions of the world. For more information or to request a consulting session at your vineyard please contact juditmonis@yahoo.com or visit www.juditmonis.com
