YOUNG VINE DECLINE: ESCA, PETRI DISEASE, BLACK MEASLES (BLACK GOO)
The last 10 years has seen a problematic increase in the number of 5-6 year old grape vines showing signs of declining health and productivity. Gubler and Mugnai have discussed the current thinking on these issues. There is also an excellent review in Wine Business Monthly and another outlining the role of Virginia's Vineyard Consultant, Lucy Morton, in identifying Black Goo as a real issue. There are two disease entities: Petri Disease aka Young Vine Decline and Esca aka Black Goo. Both lead to early loss of vines and have similar phenotypic expression of brown or black inclusions within the trunk vasculature signifying a blockage of nutrient transport. Plantings from numerous California Nurseries, exhibit typical signs of fungal infection. (Following photo from Wine Business Monthly article on Black Goo)
California in particular has witnessed massive replanting on a scale seen only with the recent reappearance of Phyloxera. The rush to replant seems to have forced nurseries to rush production at the expense of quality and indeed several major players have retired from the scene. These include VINIFERA and SONOMA GRAPE VINES. Gubler spells out the issue for growers as one of stress placed on young vine too early in life. Years of drought or overproduction, place stresses on the infected vines, leading to senescence. In years of adequate rainfall, stresses are much less and symptoms seem to disappear. They are also less in vineyards of excessive vigor. Although Gubler's discussions all seem to be centred around the grower stressing the vines and pruning wounds picking up the disease in the vineyard, rather than rootstocks coming infected, we have non-irrigated 15 year old Cabernet on SO4 rootstock which have been producing 5 tons/acre and which remain free of Phaeomoniella chlamydospora growing 10 feet from Cabernet Franc on SO4, 6 years old, in which all cuttings of wood more than 2 years old, indicate heavy infection (see photo below). Those vines in the block that have died already have had intense vascular inclusions. What is a grower to do if virtually all vines purchased currently are infected and your site has been chosen for modest vigor and therefore high wine quality?
The picture below shows a cut through the previous years growth (all green and only one annular ring) as well as a cut through 2 year wood in which the dark brown inclusions within the annular ring are apparent)
Villa Appalaccia, being a grower of predominantly Italian varietals, since 1994, had few options for vine sourcing and has purchased all vines from VINIFERA and SONOMA. We fairly early on realized that we had problems when Malvasia vines purchased from VINIFERA, started to decline. Analysis of cross sections of the trunks showed intense areas of dark brown/black vascular inclusions. Our attempts to rescue these vines have been documented in a series of photos over several years as we coped with "BLACK GOO" at Villa Appalaccia. Having observed the atherosclerotic-like events in the trunk vasculature, we became more conscious of the health of our newer plantings and have no longer retained either a high trellis or renewal spurs. Pruning during the winter, indicated the presence of these vascular inclusions in all the vines.
Samples of typical examples were sent to Department of Plant Pathology at Penn. State. The results verified that our vines were infected with Phaeomoniella chlamydospora, the causative agent in Young Vine Decline.
With the demise of these companies we purchased 1950 Aglianico plants from NOVA VINE. Examination of the newly arrived vines, indicated they too were probably as infected as materials provided by our prior suppliers. When 600 plus vines failed to push, replacements were readily provided and 15 excess of plants examined for the evidence of Phaeomoniella chlamydospora infection symptoms. One of 15 vines demonstrated clean vascular profile while the remaining vines all contained inclusions within the annual ring (previous years growth). Below are two examples of new vines, cut just above the roots. The brown inclusions, and the pinched trunk, are typical indicators of disease.
(left; clean stock, right; infected stock)
What do we do now? If we want these vines to survive 25 years, probably pray a lot. The reality is we will have to be sure to irrigate, crop low and wait 4-5 years to harvest these vines. If our vineyard site was a high vigor site, this would not be as much of an issue. Unfortunately, there are very few high vigor sites anywhere that produce great wine grapes and we do produce very fine Eastern wines. This not just an annoyance but a real challenge as we have had to use a much more labor-intensive training system in which fruit canes need to be replaced every year to retain the least amount of old wood. This more than doubles pruning labors. Vines purchased prior to 1994, do not have these fungal diseases and are spur pruned in a very short period of time. Loss of vines in this older group has been solely the result of Grape Root Borer.
Stayed Tuned!: We plan to update the progress of these vines and will train a fraction of them with the more convenient spur training and document the influence of fungal infection on training requirements. The bottom line for now is BUYER BEWARE!