Rain and water mold threaten to damage Dutch potato harvest in the long term

The heavy rainfall in recent months is causing problems for potato farmers. This is not only because the potato plants have to be planted late but also because a water fungus is spreading. This problem could affect consumers' pockets for years to come.

Because of the rain, farmers in many areas could only plant later or not at all. Rotting also occurs in some places because the potatoes are under water for a long time, says arable farming specialist Arjen Brak from the agricultural organization LTO. "There will be no peak yields. These are the 12 wettest months in a row ever."

Last year's rain was also disastrous for farmers. The notorious water mold Phytophthora has become a major problem in these wet years. Researcher Geert Kessel from Wageningen University & Research (WUR) describes the wet conditions as "Valhalla" for the potato blight.

"It started very early. In April and May, there were already plants with Phytophthora, whereas normally, you don't see them until around this time in June," he says. "By the time Phytophthora gets a grip on the plants, a plot can be dead within one to two weeks."

The water mold spread particularly well because a variant was introduced from Denmark in 2021, which later proved to be resistant to the usual protective agents. In addition, potatoes were still in the soil last year but were not harvested due to the wet conditions. Kessel says the resulting plants could be a kind of "booster" for Phytophthora.

Andries Middag, director of the Potato Processing Industry Association, warns that the potato disease will continue to cause headaches for a long time to come. This is because water mold regularly attacks seed potatoes, i.e., potatoes planted in the ground to grow new potatoes. "If we don't get it under control, it will have a major impact."

It will affect prices, says Middag. This is because the demand for potatoes remains the same while the supply shrinks. They have become more than 25 percent more expensive in the supermarket in the last two years, according to figures from Statistics Netherlands.

Kessel agrees that the water mold can cause problems for a long time because it survives in the potato tubers. "Growers are doing everything they can to prevent infestation of seed potatoes, but in a season like last year, that doesn't work so well. This also has a global impact, as the Netherlands is the world's largest exporter of seed potatoes.