Japan is alarmed by an unusual swarm of fruit-feeding stink bugs

Japan is preparing for a swarm of stink bugs that can attack fruit trees; an unusually high number of prefectures have already issued warnings.

Of Japan’s 47 prefectures, 30 from west to east, including Tokyo, had issued stink bug warnings as of Friday, according to data from the Ministry of Agriculture, Forestry and Fisheries.

This figure contrasts with the previous decade, when the number of prefectures issuing stink bug warnings between January and May averaged about five but never rose above 15.

The number of insects is already increasing and is likely to increase further after the breeding season in summer.

The attached photo shows a polished green stink bug. (Photo courtesy of Chiba Prefectural Agriculture and Forestry Research Center) (Kyodo)

Higher temperatures appear to be one of the factors contributing to insect infestation.

They benefited from an abundance of food in the fall, such as cedar and cypress nuts, and a significant number of them appear to have survived the warm winter, said Mantaro Hironaka, an associate professor specializing in entomology at Ishikawa Prefectural University.

In Japan, three species of stink bugs – the brown-winged green stink bug, the marmorated brown stink bug and the polished green stink bug – are considered major pests that cause damage to on-branch fruits, including apples, pears and peaches, by feeding on the pulp.

“We are asking (farmers) to visit their farms regularly,” a ministry official said. Protective measures include spraying chemicals and bagging fruits.

So far this year, stink bug warnings have been issued mainly in prefectures in the warmer western parts of the country. The first warning was issued in Ehime on March 22.

Chiba Prefecture, east of Tokyo, considered one of the country’s largest pear producers, issued a warning this month for the first time in a decade. Staff conducting a survey at 10 locations in the prefecture in April discovered more than seven times the usual number of stink bugs.

Experts warned that possible outbreaks should also be expected in cooler regions of the country, as corresponding warnings had been issued in the past in prefectures in northeastern Japan.

Stink bugs owe their name to the fact that they secrete a fluid from glands between their legs, which usually has an unpleasant smell.

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