Beziehungen zwischen Klimafaktoren und dem Stiellähmebefall bei Riesling x Sylvaner
DOI:
https://doi.org/10.5073/vitis.1986.25.8-20Keywords:
stiellaehme, climate, temperature, flower biologyAbstract
Correlations between climatic factors and the occurrence of stiellaehme on Riesling x Sylvaner
At Wädenswil, correlations between climatic factors and the occurrence of grape peduncle necrosis (stiellaehme) of Riesling x Sylvaner were investigated. In a long-term programm (1976-1984), the percentage frequency of stiellaehme observed in a particular plot was correlated with the mean 13.30-hour-temperature (T13 .30) and the amount of precipitation determined for five periods of grapevine development (03-19: before bud hurst ('Wollstadium') until beginning of flowering; 19-25: flowering period; 25-35: first phase of berry growth; 35-36: veraison; 36-38: second phase of berry growth). Only for the flowering period significant correlations to the occurrence of stiellaehme exist, with correlation coefficients of r = -0.94 for the mean 13.30-hour-temperature and r = 0.79 for the precipitation. For the flowering period, other climatic factors gave significantcorrelations as well: two additional mean temperatures (daily maxima and daily mean), the sum of the 13.30-hour-temperatures above 15 °C and the mean duration of sunshine. The correlations of precipitation, duration of sunshine and the sum of the temperature above 15 °C are not causal because these values are highly correlated with the mean temperatures.
In a short-term programme (1984), the flowering periods and the occurrence of stiellaehme in 659 grapes from 28 vines were recorded. The influence of climatic factors on the frequency of stiellaehme was investigated in one year by group comparison of grapes exposed to various weather conditions. Only the mean temperatures lead to significant correlations e. g. the mean 13.30-hourtemperature with r = -0.98. The equations of the regression lines from the long and short-term programmes are not identical, suggesting that factors other than temperature exert an influence.
Nevertheless, the results clearly show that the level of stiellaehme is largely determined by the mean temperature during the flowering period. The data suggest that during the flowering period an irreversible metabolic process occurs in the flowers/berries, the effects of which are apparent only after veraison.
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