Member Inquiry: Vineyard Flooding

Paul, I recently saw on the news that Temecula suffered considera­ble flood damage during the heavy rains. Were the vineyards affected? What other natural foes threaten the vine?    – L.L., Woodland Hills

Luckily, for the wineries, the damage was confined mostly to “Old Town” Temecula and a few roads which were washed out. The 1400 foot plateau which consti­tutes Temecula’s main growing area exemplifies good drainage. The vines, lying dormant this time of year, remained untroubled by the downpour. Had this occurred during the growing season, the out-come might have been devasta­tion.

If it should rain (or hail) during blooming, flowers get destroyed. A light crop results. Rains which arrive late in the ripening period, tend to delay ripening, especially if they are followed by several humid days. This can result in lowered quality, and sometimes leads to complete loss through berry crack­ing, bunch rot and other maladies. Even without rain, excessive hu­midity and fog can bring similar harm, as they encourage mildew on the leaves and can cause exten­sive berry damage.

Another foe is wind damage. High winds can break off tender shoots, resulting in crop reduction. They can rip leaves off which im­pairs the vine’s ability to produce sugar and mature the fruit. Late in the season, heavy winds can dam­age ripened grapes by whipping or by exposing them to the sun.

Sunburn poses a threat, as does any extreme temperature condition. When temperatures reach 105° F. or more, grape berries are likely to suffer severely. Exposed to the di­rect sun in such temperatures, grapes become raisin-like and cara­melized in flavor, to the detriment of any wines made from them. In the spring, after the shoots have begun to develop or, as winter ap­proaches, before the vine has gone dormant, below-freezing tempera­tures can affect the amount or qual­ity of the fruit. They can also seri­ously damage and even kill vines.

Like any other plant, the vine is prey to all sorts of insects. And it sees its share of troubles from as­sorted viruses and funguses, even from Botrytis, the so-called “noble mold”. This mold turns white grapes into luscious dessert wines, but it renders a red-wine crop unusable if it has affected more than 20% of the grapes.

A promising note: using a fairly simple form of genetic engineering pioneered at U.C. Davis, it looks possible to develop plants particu­larly resistant to specific pests, dis­eases and environmental threats. Vine cells are artificially cultured and then exposed to the phenome­non to which resistance is re­quired. This so-called “mutant se­lection” system (Mutant Ninja Grapevines?) is less cumbersome and much faster than propagation in the nursery.

— P.K. Jr.

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