1. Weather

The summery weather at the beginning of May with temperatures of up to 27°C was followed by a cool, rainy phase with a significant drop in temperature to below 15°C. In the second decade of May, dry weather set in with moderate daytime temperatures of up to 22°C and sometimes very cool nights with temperatures below 5°C. The last two weeks of May were characterized by changeable weather with frequent rainfall and mostly cool temperatures below 18°C. At 71.2-79 mm/m², the amount of precipitation in the Tettnang growing region was well below the long-term average of 116.9 mm/m² and thus approx. 35% lower.

2. growth status

The stocks in the growing region generally developed well. Growth was initially rapid, but was slowed down considerably due to the cool weather and low rainfall. The late-cut landraces in particular lagged behind.

3. cultivation measures

The spring work was all completed on time due to the long dry spells and moderate growth. In the second decade of May, the first cultivation of the early-cut varieties began. The second nitrogen application was optimally placed before the rainfall. The last stands of the “Tettnanger” variety were instructed by the end of May.

4. occurrence of diseases and pests

Peronospora primary infections in the form of “bubble heads” occurred more frequently in the cultivation area. However, similar symptoms were also caused by cold damage from the sometimes very cool nights. The Peronospora warning service was started on 12.05.2025. The bad weather period in the last two weeks of May led to an increase in sporangia numbers in the spore traps and to a first warning call against Peronospora secondary on May 26. Pustules caused by powdery mildew were not yet observed in May.

The earth flea, which occurred rather moderately this year, was only an issue in the late-cut landraces. Aphis fly infestation began at the beginning of May due to the warm temperatures. The dry weather later on ensured a steady influx, which weakened somewhat with the cool, rainy weather at the end of May. The colonization of the leaves with aphids continued to increase, so that individual areas reached the control guideline value at the end of May. Colonies of the black bean aphid were observed on some young vines. In the known “hotspots”, the first spider mites were on the move from mid-May.

Text: Daniel Hagl and Dr. Michael Cieslak, LTZ Tettnang