Sales in the July-to-September quarter retreated to $2.62bn from $2.98bn a year earlier, the Basel, Switzerland-based company said in a statement on Thursday.
The result fell short of the analyst forecast of $2.71bn.
Syngenta also warned that the recession in Latin America and the strong U.S. dollar may weaken its 2015 earnings.
Earnings before interest, taxes, depreciation and amortization that aren’t stripped of currency fluctuations will likely show a “mid-single digit decline,” compared to a previous prediction for it to remain at the 2014 level, Syngenta said in the statement.
Brazil's real touched a record low last month, hit by a political crisis coupled with an economy in slowdown.
ADRs of Syngenta rose 1% to $63.58 at 10:44 a.m. in New York, erasing an earlier loss.
Syngenta's management turned down the deal, saying it undervalued the company.