Effects of copper fungicide spraying on volatile thiols of the varietal aroma of Sauvignon blanc, Cabernet Sauvignon and Merlot wines

In a three-year experiment, the effect of pre-veraison copper sprayings of vines on must composition and some volatile thiols contributing to the varietal aroma of Sauvignon blanc, Cabernet Sauvignon and Merlot wines was studied in comparison with folpet sprayings in the Bordeaux winegrowing region. The readivity of copper residues with thiols, mainly during the alcoholic fermentation, had a dramatic effect on the concentration of 4-mercapto-4-methylpentan-2-one and 3-mercaptohexanol in wines. However, copper sprayings, preferentially on the foliage, did not significantly increase copper residues in must; thiol concentrations in wines were very close to those found in wines obtained from vines sprayed with folpet. Therefore, this mode of spraying can be used to avoid the effects of copper treatment at veraison on the volatile thiols of the wines varietal aroma.

La protection du vignoble contre les maladies en l'an 2001

La protection du vignoble contre les maladies en l'an 200

An analysis of the effects of environmental factors on conidial dispersal of Uncinula necator (grape powdery mildew) in vineyards

Aerial spore concentration of #Uncinula necator$ (the causal agent of grape powdery mildew), weather data and croping practices were monitored during two consecutive seasons in two vineyards of the Bordeaux area. During days with no rain, spore dispersal was mainly diurnal and showed variations that followed the same pattern as that of wind speed, and a reverse pattern to that of relative humidity. Light falls of rain, of approximately 2 mm, coincided with increased spore densities in the air. Pesticide sprays using high pressure equipment generated high wind speeds at the canopy level. This may trigger high spore dispersal. High conidial stocks were produced under spontaneous conditions in the canopy. These stocks were released only under particular events, such as heavy rains, or pesticide applications with high pressure sprayers. Other cropping practices causing leaf shaking, such as pruning, may enhance spore dispersal. Over the observation period, the onset of spore dispersal was observed during a period with no rain following a rainy period, suggesting the detrimental effect of rains on epidemic onset. Epidemiological and disease management implications are discussed. (Résumé d'auteur

Etudes sur les propriétés et le mode d'action des nouveaux fongicides antimildiou chez la vigne

Etudes sur les propriétés et le mode d'action des nouveaux fongicides antimildiou chez la vign

La lutte chimique

La lutte chimiqu

Effects of wind, relative humidity, leaf movement and colony age on dispersal of conidia of Uncinula necator, causal agent of grape powdery mildew

A wind tunnel was designed to study the effect of wind, relative humidity, leaf movement and colony age on dispersal of conidia of #Uncinula necator$. Wind speed as low as 2.3 m/s instantaneously triggered dispersal of conidia from fixed leaf discs of 18-day-old infections. Conidia were observed on sporulating leaf discs even after exposure to 17 m/s wind. The fraction of conidia dispersed at a given wind speed increased with colony age from 12 to 24 days. Conidia of 27-day-old colonies were less easily dispersed. No gradient of maturation of conidia along the conidial chain was observed, suggesting that even newly formed conidia were able to germinate after dispersal. Germination of dispersed conidia decreased slightly with greater colony age. Both wind and simulted raindrops caused dispersal of conidia from infected leaves. Leaf movement at wind speed of 3.5-4 m/s increased dispersal, and the first impact of three simulated raindrops caused release of 53% of the total conidia dispersed. Relative humidity had no effect on dispersal of conidia at different wind speeds. (Résumé d'auteur

La lutte intégrée

La lutte intégré