Liu Mingsuo, a first-year watermelon grower in eastern China's Jiangsu province, said he sprayed forchlorfenuron, a growth accelerator, and instant calcium on his melons May 6.
"The next day, about 180 watermelons burst," he told the official Chinese news agency Xinhua.
Experts who investigated the unusual episode that may have ruined more than 115 acres of melons told Xinhua Tuesday the use of the growth promoter, combined with sudden rainfall after a dry spell and the type of melon planted, appeared to be responsible.
Liu was the only grower in the area who had used forchlorfenuron and it appears his timing was off, Xinhua said. The calcium was not a factor in the bursting problem, the experts said.
However, farmers who did not use forchlorfenuron also said they had bursting melons, as well.
It is normal for about 10 percent of watermelons to burst, said Xu Jinhua, with the Jiangsu Academy of Agricultural Sciences. "The bursting rate often has something to do with the melon variety, weather and so on."
Forchlorfenuron is allowed in China. In the United States it is used on kiwifruit and grapes.
"The chemical is safe as long as the right amount is used. And there is sometime before the fruits hit the market and forchlorfenuron residue is often too little to detect, so it basically has no side effects on people," Wang Liangju, professor with Nanjing Agriculture University, said.