Crop disease hits production of sweet potato shochu

By Masahiro Kozono / Yomiuri Shimbun Staff Writer

15:17 JST, October 29, 2022

KAGOSHIMA — A crop disease has caused a chronic shortage of sweet potatoes, forcing producers of shochu made from the tuber to raise prices and suspend sales.

Stem rot was first confirmed in Japan four years ago. Since then, the sweet potato harvest has decreased by about 30% over three years, with no signs of the infection easing.

Shochu distiller Hamadasyuzou in Ichikikushikino, Kagoshima Prefecture, has suspended sales of some of its products. “I never thought there would be this much of a sweet potato shortage,” said Yuichiro Hamada, the CEO of the company.

Soaring prices of fuel and materials such as packaging supplies are also hurting the company. The distiller raised the prices of its shochu by about 8% on Oct. 1. “We had no option but to raise prices,” Hamada said.

Stem rot was discovered about 100 years ago in the United States before spreading to South America. In recent years, it has also been confirmed in China and South Korea.

It was detected in Okinawa and Kagoshima prefectures in 2018 and has now been confirmed in 27 prefectures in Japan, including Tokyo. The spread of the disease has been attributed to the distribution of infected seed potatoes and seedlings.

Kagoshima Prefecture, which boasts the largest sweet potato production in the nation, harvested 278,300 tons in 2018, but the figure has decreased every year since then, slumping to 190,600 tons in 2021, down by 30% from 2018.

According to the Kagoshima prefectural government, stem rot has been confirmed at least once in as much as 75% of the farmland in the prefecture. As a result, the size of the harvest has decreased and prices have gone up.

The situation is a massive blow to sweet potato shochu producers.

Shochu makers started raising prices in spring, with the price of a bottle going up by about 10%, according to the Kagoshima Shochu Makers Association and others.

Satsuma Shuzo in Makurazaki, Kagoshima Prefecture, raised prices by an average of 8% in October. Most manufacturers in the prefecture will likely follow suit by the end of the year.

The nation’s largest distributor of sweet potato shochu, Kirishima Shuzo Co. in Miyakonojo, Miyazaki Prefecture, raised the price of its mainstay Kuro Kirishima in September. In October, Unkai Shuzo Co. in Miyazaki City also increased its prices.

Efforts to stop the rot

The central government and the Kagoshima prefectural governments are urging farmers and others to install a vapor heat treatment system that disinfects seed potatoes, and equipment costs are being subsidized.

Pathogen-free seedlings are also thought to be an effective way to combat the disease.

A national research organization has developed a new sweet potato variety called michishizuku, which shows high disease resistance and has a flavor similar to that of koganesengan, a mainstay variety used to make shochu.

However, the association believes the tough times will likely continue for a while as it will take at least three years for these measures to bear fruit.

Shochu made from sweet potato grown in Kagoshima Prefecture, part of which comprised an old province called Satsuma, has been marketed as Satsuma Shochu since 2005 under Japan’s Geographical Indication system.

However, Kagoshima producers have expressed concern that the current situation will have an impact on the reputation of the regional label. Some have told the association they will have no option but to use sweet potatoes produced outside the prefecture if the situation continues.

“The ‘brand’ we have built will be severely affected,” said Hamada, who heads the association. “If consumers continue to shift away from Satsuma Shochu, it could get even worse. We have no choice but to strive to develop products consumers will choose even after we raise prices.”