Heat and drought force Thurgau apple growers to adapt

Heat and drought have damaged this year’s apple crop in Thurgau, a Swiss canton, with harvest volumes expected to fall well below the average of recent years, SRF reports. Growers are increasingly turning to varieties that can withstand higher temperatures.

Apple grower Stefan Anderes is harvesting his crop and moving full crates of freshly picked apples into storage. But the strong-looking fruit masks the effects of the summer heat and dry conditions.

“The early varieties suffered extremely badly this year,” Anderes said. Sunburn affected the apples, while drought stress caused some trees to shed fruit. Their leaves also wilted, and the fruit developed less colour.

The unusually hot and dry summer has prompted Thurgau’s apple growers to reconsider how they operate. Warmer conditions cause trees to sprout earlier in spring, making them more vulnerable to frost. At the same time, varieties that previously could not grow in the region are now possible.

Anderes has begun restructuring his farm, which covers 10 hectares and grows varieties including Kanzi, Gala and Braeburn. Kanzi apples have performed well in the heat. Even at temperatures above 30 degrees Celsius, the trees showed no signs of stress, although their final condition will only be clear at harvest.

Anderes is also planting more varieties that ripen later in the year. This could allow him to extend the harvest into November, something that would previously have been impossible because of the climate.

More robust, heat-tolerant varieties will be needed in the long term, said Bruno Studer, a professor of plant breeding at ETH Zurich. The rootstock on which trees grow also affects their root development and water uptake, he said.

Developing a new apple variety takes time. According to the Agroscope research institute, it can take around 20 years for a new variety to reach the market. It must be tested under different environmental conditions before it can be successfully established commercially.

Older apple varieties are likely to disappear from large orchards over time. Thurgau is expected to be particularly affected because it has exceptionally large areas devoted to apple growing. In the short term, growers face fewer and smaller apples this year, although the fruit is sweeter.