Wednesday, April 23, 2014

The Vine’s Enemy: Phylloxera Vastatrix

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Posted by Burke Morton On November - 4 - 2009

photo: dogeared-1144I just got an e-mail asking, “What is phylloxera, and what does it do?” Here is a relatively brief answer (most entries on this topic are outrageously long) to a complex problem:

Any name ending in “-trix” can't be good. Whether it's a dominatrix or an Agent from The Matrix, you know there's going to be pain involved (though Beatrix Potter was certainly a benign individual...). [Okay...if it is your inclination to get bent out of shape here, I'm not making a political statement--I know full well that the '-trix' suffix is feminine (where the '-tor' suffix is masculine)--but it is an archaic form that rarely surfaces with a good meaning...when was the last time you heard the words directrix, executrix, or mediatrix? It might be fun to bring them back, however. Whatever else is true, I'm sure you'll agree that Beator is not a good woman's name.] Anyway, Phylloxera vastatrix--a dastardly scourge that only attacks grapevines--hit France in the 1860s and by the end of the decade wine growers were no doubt scanning the horizon for the four horsemen, because this root-feeding aphid wreaked destruction on vineyards across Europe (and therefore had a calamitous social and economic impact). While it is under control today, it continues to be a problem.

Phylloxera is a native of the eastern part of the United States, where it feeds on the native grape vines without doing serious damage. European wine grapes--Vitis vinifera--have no natural defenses against this microscopic louse, which came to Europe on vines imported by fanatical amateur botanists in Victorian England. Hordes of this insect (which, as you will see, are not hard to come by) eventually destroyed vineyards across Britain, and then moved to the continent, where this menace--anointed vastatrix because it was “the devastator” (and males don't live long enough to do anything other than their standard procreative function)--feasted as no pest has feasted before. The only vines that remained unaffected were those planted on soils containing high concentrations of sand or schist, as the louse does not survive well in these kinds of soil.

The Life of the Louse

As is not atypical for an aphid, phylloxera has an up to eighteen stage life cycle. This is divisible into four parts: sexual form, leaf form, root form, and winged form.

The sexual form is born from eggs laid on the bottom side of young grape leaves. The males and females mate, the females lay a single winter egg in the bark of a vine's trunk, then they both die.

From this single egg comes the female stem mother, which is the leaf form. It climbs onto a leaf, injects it with saliva (often creating a depression in the leaf that acts as a nest), and lays several eggs by self-propagation (parthenogenesis).

The nymphs that hatch from the leaves are the root form. They crawl down to the roots, perforating the surface of the root to feed on the sap, secreting a poison that prevents the root from healing. This keeps the root open for return visits, but is also the death knell for the vine. There are up to seven generations created by these nymphs over the course of the summer, each one producing females that lay more eggs (by parthenogenesis) on the roots.

The last generation of these nymphs hatch in the autumn and hibernate in the roots, and in humid areas mature into the winged form. They climb the roots with the sap in the early spring, and fly off in search of other vines to destroy (or in the case of wingless nymphs, continue to scuttle their current home), where they lay eggs on the bottom side of a young grape leaf, and the cycle begins again.

Trying to Solve the Problem

Insidious! This is geometric expansion of a single louse, involving only one sexual reproduction (the rest is essentially self-cloning). Generally, the more complex a life cycle, the easier it should be to eradicate a species. The phylloxera life cycle is apparently infinitely adaptable, because interruption of the life cycle at any stage has done nothing to halt its advance. It has proven so resilient that it is likely to stand with the cockroach in surviving a nuclear holocaust.

The solution to the destruction of Europe's wine grapes lay in grafting rootstock from American vine species onto cuttings of European grapevines. Phylloxera has proven adaptive even to that approach: a rootstock that is resistant in one country may not be resistant in another. Grafting is another topic altogether, for a later time.

A Narrative Bibliography

If you wish to do any further research, or check on mine, my reference sources include my own observations of phylloxera at work, as well as the 2nd Edition of The Oxford Companion to Wine; The Wines of Alsace by Tom Stevenson; Burgundy by Anthony Hanson; and Vines, Grapes, and Wines by Jancis Robinson.

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