Two new kinds of chemical weed killers invented by scientists of the Chinese Academy of Sciences have recently passed appraisal, according to the Beijing-based Guangming Daily.

　　The two chemical formulas are used to kill two major poisonous weeds threatening livestock in pastures -- radix euphorbiae ebracteolatae and pointvetch.

　　The chemicals can destroy the two forms of killer weeds within hours by checking their nucleic acid metabolism and protein synthesis, and will cause no harm to other edible plants or livestock.

　　The weed killers have proved effective after trial use in some places in northwest China's Gansu Province, the paper said.