China has patented a new rat poison, based on traditional Chinese medicine, that makes male rats sterile.
The Xinhua news agency reports Sunday that extensive tests show the poison can have a significant effect on rat populations.
The new poison Trypterigium wilfordii, said to be "fragrant and attractive" to rodents that consume it, was applied to 47,000 households and 5,600 work units in Shanghai. Three months later, Xinhua says, the density of rats in the affected area had declined by 30 percent. After another three months, rat density was down by 88 percent.
China previously halted production of the common pesticide tetramine after it became the poison of choice in a number of murders.
Some information for this story provided by Reuters and AP.