Stink bug outbreak across Japan sparks rice price concerns
Rice-eating stink bugs are spreading rapidly across Japan due to extreme heat and warmer winters, threatening the government’s push to boost rice supply. Farmers face rising costs for drone pesticide spraying, yet some report yield drops of over 20%. With stink bug populations surging, experts warn of worsening harvest losses and price hikes.
TOKYO – Rice-eating stink bugs are appearing in greater numbers in paddy fields across Japan, casting a shadow over government policies aimed at increasing the rice supply.
The extreme heat and warm winters seen in recent years are thought to be behind the far-reaching spread of the so-called rice stink bugs.
The bugs, known for their foul odor, prefer gramineous plants like rice. They attach themselves to a rice plant when it is forming its ear, pierce the grains with their stylets and suck out the juices. As a result, the grains develop the black or brown spots and cannot be shipped for human consumption.
Rice prices have been high in Japan since summer in 2024, and the central government is trying to deal with shortages of the grain by increasing production. But there are fears that the damage by the bugs could negatively impact the 2025 harvest, which the government has pinned its hopes on.
10% reduced harvest
In August, Seiju Suzuki, the 54-year-old president of a farming company, sighed as he held up a brown-spotted rice ear on an about 80-hectare paddy in Sugito, Saitama Prefecture.
The company’s yields fell 10% last year in rice fields that could not be sprayed with pesticides, he said. The company has introduced a new drone for aerial pesticide spraying, which has a heavy cost burden. In addition to an initial investment of ¥3 million, the chemicals used for each spray come with a price tag of about ¥500,000.
The company has expanded its business by incorporating nearby abandoned farmland, increasing the area of its rice paddies by more than 30% over the past 10 years. The larger paddies now accommodate a wide range of rice varieties, from those harvested very early — at the end of July — to those harvested in mid-September.
Last year, the company sprayed its crops with pesticides twice. This year, it added a third application in mid-August, as the rice-growing season has become longer. Nevertheless, harvests of some rice varieties in the company’s fields have seen a drop of more than 20% compared to average years.
The damage caused by stink bugs cannot be ignored.
The number of stink bugs clinging to combine harvesters is also increasing.
Overwintering bugs
Last year, 31 prefectural governments issued 39 stink bug warnings, according to the Agriculture, Forestry and Fisheries Ministry. This year, however, 35 prefectures had issued 46 such warnings as of the end of August, the highest in 10 years.
After rice has been harvested, adult stink bugs migrate to nearby woods and other areas, where many of them die in the winter because they are said to be sensitive to the cold. However, winters have become warmer in recent years, and more of the bugs are thought to be surviving through the season.
The Saitama prefectural government, which has issued three warnings this summer alone, conducted a survey on the number of rice stink bugs that had overwintered and confirmed that the bug’s population was 46 times larger this year than last.
Intense summer heat may also be contributing to expanding insect populations, with some research showing that sustained high temperatures of 35 C or higher shorten the time it takes for insects to reach adulthood.
Impact on rice prices
Japan aims to increase rice production by 560,000 tons this year. The figure is based on an analysis that found that the rise in rice prices is due to rice production failing to meet demand by a total of 760,000 tons over the past two years.
One factor that greatly influences harvest yields is the ratio of white rice obtained from brown rice, known as the rice milling yield. For the 2023 and 2024 rice crops, this figure is expected to fall by 0.8-1.4% compared to average years, leading to a production decrease of 160,000 tons. Although high temperatures have contributed to a decline in rice quality, the damage caused by stink bugs is a factor that cannot be ignored.
The government has begun emergency support measures to help farmers with the cost of purchasing such thing as pesticides, citing a need to prevent stink bug damage and stabilize supply, demand and prices.
“Stink bugs are believed to travel long distances, several kilometers, so localized measures are ineffective,” said Yuta Iwahashi, a researcher at the Hyogo prefectural pest control center. “It is essential to take measures like systematically spraying pesticides throughout the region.”
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Source : ANN
