Japan is slipping toward a banana shortage crisis, the latest disruption linked to the Middle East conflict.

The reason: the country ships in the tropical fruit while it’s still green, then ripens it in rooms filled with ethylene before bunches reach store shelves. Supplies of the naphtha-derived gas are running low in an economy that imports more than 90% of its crude oil.

Japan bought about 1 million metric tons of bananas last year, making the fruit one of the country’s most important grocery staples. Naphtha inventories are down by a quarter so far this year, as the closing of the Strait of Hormuz continues to choke off a fifth of the world’s petroleum supplies. The resulting shortage is the worst in five decades, according to Eiji Akashi, secretary general of the Japan Banana Importers Association.