Coulure

Coulure
Not to be confused with Collioure AOC.
Young grapes are most susceptible to coulure right after flowering when they need vital carbohydrate resources in order to develop fully.

Coulure (pronounced coo-LYUR) is a potential viticultural hazard that is the result of metabolic reactions to weather conditions that causes a failure of grapes to develop after flowering. In English the word shatter is sometimes used. Coulure is triggered by periods of cold, cloudy, rainy weather or very high out-of-season temperatures. The condition is most often manifested in the spring. It also occurs in vines that have little sugar content in their tissue. Flowers stay closed and are not fertilized. Thus the vines are not pollinated as the grape fails to develop and falls off. Coulure can also cause irregular bunches of grapes which are less compact than normal. These bunches are more sensitive to developing various grape diseases. The yield of a vine with coulure will decrease substantially. Grape varieties with high proclivity to coulure are Grenache, Malbec, Merlot, and Muscat Ottonel. Other causes of coulure may be vineyard conditions and practices, pruning too early or too severely, excessively fertile soils or overuse of fertilizers, and improper selection of rootstocks or clones.[1]

Contents

Cause and effect

Grapevines need a balance of sufficient leaf cover in order to produce photosynthesis but not shade the grapes too much from sunlight.

Coulure is caused by a carbohydrate deficiency in the plant tissues that causes the vine to conserve resources that would otherwise be funneled into the developing grape berries. As carbohydrate levels drop, soon after flowering the stems connected to the berries shrivel as the small grapes (0.2 inches/5 millimeters in diameter) eventually fall off. To some extent coulure and the dropping of fruit is a natural and healthy reaction of a vine that is self regulating its resource and the amount of fruit that it produces. But when the situation is exacerbated by certain weather conditions and disruption to photosynthesis, coulure can have a more severe impact on yields that may negatively affect a region's grape supply and thus influence pricing.[1]

When the weather is the primary instigator of coulure, the French term this phenomenon coulure climatique. This describes the cloudy and wet conditions that limit the amount of photosynthetic activity that takes place during the flowering cycle of a grapevine. Limited sunshine means lower sugar levels that can be converted into resources to develop grape berries. Warm temperatures can also exacerbate coulure in some grape varieties by promoting cellular respiration and excessive shoot growth that further competes with the berries for the resources derived from carbohydrates. Other contributing include excessively fertile vineyard soils, either naturally or enhanced by the use of nitrogen-rich fertilizers, overly vigorous rootstock and severe pruning that too drastically limits the amount of leaf surface needed to sustain photosynthesis.[1]

Prevention

Malbec can be highly susceptible to coulure but newer clones are being produced with less sensitivity.

Coulure is not 100% preventable but a vineyard manager can take several precautions to lessen the severity and impact of coulure. Some grape varieties are more prone to develop coulure than others, such as Grenache, Malbec, Merlot and Muscat Ottonel. A grower can choose to grow clones of those varieties, now commonly available for Merlot and Malbec, that have less susceptibility to developing coulure. In the vineyard, care can be taken to not prune so severely and insure that there is adequate leaf coverage for photosynthesis. Trimming the tips of developing shoots near the end of the flowering period can lessen the competition for sugar resources between berries and new shoot development. For non-organic viticulture, chemical growth inhibitors can be applied to the vine to limit shoot growth as well.[1]

See also

References

  1. ^ a b c d J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 207-208 Oxford University Press 2006 ISBN 0198609906

External links


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Look at other dictionaries:

  • coulure — [ kulyr ] n. f. • 1331; coleüreXIIIe; de couler 1 ♦ Mouvement d un liquide qui s écoule, et par ext. Traînée d une matière molle qui a coulé. Coulures de bougie, de peinture. (1690) Techn. Partie du métal en fusion qui coule à travers les joints… …   Encyclopédie Universelle

  • coulure — COULURE. s. f. Il se dit en parlant Des grains de la grappe qui tombent ou se dessèchent quand le raisin commence à se nouer. La vigne est sauvée de la gelée, il n y a plus que la coulure à craindre.Coulure, se dit aussi De la portion du métal… …   Dictionnaire de l'Académie Française 1798

  • coulûre — Coulûre. subst. fem. La chûte des grains, de la grappe, qui se perdent avec la fleur. La vigne est sauvée de la gelée, il n y a plus que la coulûre à craindre …   Dictionnaire de l'Académie française

  • Coulure — Cou*lure , n. [F., prop., a dropping.] (Hort.) A disease affecting grapes, esp. in California, manifested by the premature dropping of the fruit. [Webster 1913 Suppl.] …   The Collaborative International Dictionary of English

  • coulure — de vignes, Roratio …   Thresor de la langue françoyse

  • Coulure — En arboriculture fruitière et en viticulture, la coulure est la chute des fleurs ou des jeunes fruits. Causes La coulure peut être due à : de mauvaises conditions climatiques avant et pendant la floraison. La pluie fait couler le pollen (d… …   Wikipédia en Français

  • coulure — (kou lu r ) s. f. 1°   Mouvement d une chose, d un liquide qui coule. Ce que les fondeurs craignent le plus, c est la coulure du métal hors du moule. 2°   Terme de culture. Accident qui arrive à la grappe en fleur et qui fait que tout ou partie… …   Dictionnaire de la Langue Française d'Émile Littré

  • COULURE — s. f. Il se dit en parlant Des grains de la grappe qui tombent ou se dessèchent quand le raisin commence à se nouer. La vigne est sauvée de la gelée, il n y a plus que la coulure à craindre. COULURE, se dit aussi de La portion du métal qui s… …   Dictionnaire de l'Academie Francaise, 7eme edition (1835)

  • COULURE — n. f. Ce qui s’écoule, en parlant du Métal qui s’échappe par les interstices du moule et des Grains de la grappe qui tombent quand le raisin commence à se nouer. Il se dit aussi de Ce qu’on fait couler, enfoncer. Les coulures d’un filet, Les… …   Dictionnaire de l'Academie Francaise, 8eme edition (1935)

  • ulure — coulure foulure moulure roulure tubulure vermiculure vermoulure échauboulure …   Dictionnaire des rimes

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