Standard and Poor's has cut Nufarm's credit rating of Nufarm to junk status.
The Australian farm chemicals firm recently halved its profit forecast for the current financial year and began talks with lenders to ease its funding commitments.
Nufarm's long-term rating has been lowered from BB to BBB- and the agency says it could fall further as the company seeks to refinance $A300 million over the next six months.
The company is forecasting a full-year profit of between $A55 million and $A65 million because of difficulties selling its main weedkiller, glyphosate.
Nufarm is 20% owned by Japan's Sumitomo Chemical.