Monsanto Co , the world's biggest seed company, posted a 14 percent drop in quarterly earnings on Wednesday and said it planned a restructuring that would cut about 900 employees and separate its declining herbicide business.

St. Louis-based Monsanto, a leader in development of genetically modified crops, said net income for the third quarter totaled $694 million, or $1.25 a share, falling from $811 million, or $1.45 a share, a year earlier.

Analysts on average were expecting $1.18 a share after a warning by the company last month of lower earnings due to tougher competition in the herbicide business.

Monsanto shares rose 3.2 percent to $81.85 in premarket trade on Wednesday.

Net sales net sales of $3.2 billion for the quarter were down 11 percent due in part to declines in the company's Roundup and other glyphosate-based agricultural herbicides globally.

(Reporting by Carey Gillam, editing by Dave Zimmerman )