Dead Arm Disease Makes For A Delicious Wine
Anyone who has ever had a garden, or raised a plant or two, is pained at the signs of unhealthy vegetation. Is it something you can remedy, like providing more (or less) water? Applying an all-natural pesticide? Simply removing the dead foliage?
Vineyard owners face the same plights as we do, but on a much larger scale. And like us, sometimes they don’t always have a remedy. Dead Arm is one of many grapevine diseases, and unfortunately it doesn’t have a cure. But grape growers and wine makers have a unique solution for how to deal with Dead Arm before it ravages their vines completely – they continue to make delicious, super-concentrated juice from the surviving grapes, despite the disease!
So What Exactly Is Dead Arm?
Dead Arm is actually a catch-all term for multiple diseases that cause wood rot within the trunk and shoots, or “arms”, of a vine. The disease is not exclusive to just grapes, and can also infect other crops such as apples, pears, stone fruits, almonds, pistachios and walnuts. Several different fungi are responsible, with the main culprits being Eutypa lata or Phomopsis viticola. If you are not familiar with the term Dead Arm, you may be familiar with some of the other names the disease is known by – dieback, grape canker, cane spot, or esca (black measles). Early symptoms include stunted growth of the arms, discoloration and curling of the leaves, and rotten fruit with purple, brown or black cankers. As the disease progresses, the entire portion of the vine affected will shed its foliage, leaving behind nothing but bare, rotten wood – or a Dead Arm.
How Do Grapevines Become Affected?
The short answer? Pruning and rain.
The long answer? Let’s go back to biology class. Fungi in general love moisture, and many species in particular also love wood. When fungi reproduce, they do so by releasing spores into the environment. Rain and wind help to spread these spores to new hosts, and if they find a hospitable environment, inoculation (and ultimately, infection) occurs.
When these pathogenic organisms encounter freshly pruned vines, the spores settle into the exposed vascular tissue, similar to the way dangerous bacteria find their way into an exposed wound. The fungal cells proliferate and reproduce within the arms of the vine, even before symptoms are visible to the grower. In fact, symptoms can take more than a year to emerge, and are usually only seen in vines older than 8 years of age – even if the infection occurred when the vines were as young as 5.
So What’s A Grape Grower To Do?
Remove – The grower has two options for removing the diseased vines from his crop. He can locate where on the trunk there may still be healthy plant tissue, and remove the dead material only. The vine may produce healthy growth, but there is still chance of infection if the grower does not take proper remediation steps. The second, and safest option, is to completely remove all of the affected vines from the crop. The trunk of the Dead Arm must completely be removed from the ground, including the roots, because the whole plant system is likely to be infected with the disease. A cautious grower may also want to remove any neighboring vines to ensure complete eradication of the fungus. In both scenarios, the diseased plant matter should be completely destroyed when removal is complete.
Remediate – To ensure the crops will not become re-infected, the grower should think about adopting a few remediation policies:
- Limit or decrease pruning
- Delay pruning, or only prune during dry periods
- Apply pruning-wound protectants, wood sealants, boric acid or essential oils known to be safe on grapevines
- Adopt sanitation techniques using appropriate fungicides
Drink Up – Yes, you read that right! Dead Arm can actually be a thing of beauty. Remember, wine is basically rotten fruit. So why can’t a rotten tree produce really good wine, too? When Dead Arm begins to kill off part of a vine, the remaining portion still is able to produce fruit. These grapes are able to obtain all the extra sugar, nutrients and flavors that would have been going to their neighbors on the other side of the vine. In turn, all this extra oomph makes for some really spectacular grapes. Spectacular grapes = spectacular wine.
Don’t believe me?
Try It For Yourself!
d’Arenberg (McLaren Vale, Australia) is king of Dead Arm – they named their Shiraz after it. If you can get your hands on a bottle, you won’t regret it (worth the $65 price tag). The flavors are super concentrated, and unlike any other Shiraz I have ever tasted. This is a beautiful, complex and wonderfully structured wine. It’s like a gift that keeps on giving. Intoxicating aromas of damp mossy earth, mushrooms, a little barnyard funk, and fermented cherries. You can definitely tell the vines have been affected by the fungus this is named after. Rich, dense, full flavors of eucalyptus, sweet tobacco, mushroom, blackberry and black currant jam. The layers are long, oils thick, and off dry. The finish is more eucalyptus and lasts for days.
Ultimately, Affected Vines Will Succumb To The Disease
But that doesn’t mean we can’t enjoy the beauty that nature is providing to us along the way, if we learn how to properly control and manage Dead Arm. Drink up, as long as the grapes keep on giving!
“Dead arm of grapevine.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 15 Mar 2017. Web. 15 Aug 2017. https://en.wikipedia.org/wiki/Dead_arm_of_grapevine
“Eutypa Dieback.” UC Pest Management Guidelines. Regents of the University of California, 21 Jun 2016. Web. 15 Aug 2017. http://ipm.ucanr.edu/PMG/r302100611.html