Photo/Illutration Harvested mushrooms on sale at a farm stand in Minamimaki, Nagano Prefecture, in late October (Kazuki Endo)

NAGANO—The heat wave and low rainfall this year have delayed and decimated harvests of mushrooms, an autumn delicacy, in the usually productive mountains of Nagano Prefecture.

Mount Jizukiyama, a 733-meter-high peak in the central part of the prefectural capital, is known as a “mushroom mountain,” where a variety of edible fungi grow in September.

However, Isamu Kobayashi, a member of a group that maintains hiking courses on the mountain, says the situation this year has been unprecedented.

“There are no mushrooms growing, even poisonous ones, perhaps because of the abnormal weather,” he said in September.

Kobayashi, 77, said the situation has been similar on Mount Iizunayama in Nagano’s northern Togakushi district, where he is from. He said mushroom growth there was delayed until October.

According to the Iiyama Central Market, a wholesale market for foodstuffs from in and around Iiyama, some mushrooms that are normally picked early in autumn were not brought in until October, more than one month later than usual.

The supply has been low, but prices have not been significantly affected.

“Mushrooms are often used in hot-pot dishes,” Masateru Takizawa of the Iiyama Central Market said. “Demand has not increased due to the prolonged hot weather, and prices have stayed at average levels or even lower than in a normal year.”

Kazuhiko Masuno, a researcher at the Nagano Prefecture Forestry Research Center who is familiar with mushroom growth, said the overall amount of mushrooms that grow in autumn has been reduced due to the heat and drier weather this year.

“The harvest season for all mushrooms is about one month behind schedule,” said Masuno, 66.

According to the Nagano Local Meteorological Observatory, the average temperature in central Nagano was 28.2 degrees in August, which was 2.8 degrees higher than in a normal year, and 24.5 degrees in September, 3.5 degrees higher.

Rainfall in central Nagano was 85.0 millimeters in August, 76 percent the amount in a normal year, and 71.5 mm in September, only 57 percent.

The entire prefecture in central Japan experienced a similar pattern, with average temperatures in August and September being the highest in most locations since statistics began.

Mushrooms have difficulty growing in dry conditions.

The harvest season appears to have been delayed until October or even later, when precipitation finally increased and temperatures dropped to levels suitable for growth.

The effects of abnormal weather also extended to matsutake mushrooms, the coveted delicacy for which Nagano Prefecture is known.

According to a prefectural government survey, producers in all regions said there was “almost no harvest” in September, when matsutake mushrooms usually begin to appear on store shelves.

Even in October, when the harvest usually reaches its peak, producers said mushroom haul continued to be “considerably less” than in a normal year.

Last year, Nagano Prefecture produced 22.6 tons of matsutake mushrooms, accounting for more than 60 percent of domestic production. Iwate Prefecture in northeastern Japan was a distant second with 6.5 tons.

But officials said there is a possibility that production volumes in the two prefectures could switch.

Masuno at the Nagano Prefecture Forestry Research Center is concerned that mushroom growth will be severely impacted if autumn periods are shortened due to effects of climate change and other factors.

“Mushroom harvests will continue to decrease if winter sets in after abnormal weather conditions cause high temperatures to persist into autumn,” he said.

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