Litigation
In 2001, the United States Patent and Trademark Office ruled in favor of Syngenta which had filed a suit against Bayer for patent infringement on a class of neonicotinoid insecticides. The following year Syngenta filed suits against Monsanto and other companies claiming infringement of its U.S. biotechnology patents covering genetically modified corn and cotton. In 2004, it again filed a suit against Monsanto, claiming antitrust violations related to the U.S. biotech corn seed market, and Monsanto countersued. Monsanto and Syngenta settled all litigation in 2008.
Syngenta was the defendant in a class action lawsuit by the city of Greenville, Illinois concerning the adverse effects of atrazine on human water supplies. The suit was settled for $105 million in May 2012. A similar case involving six states has been in federal court since 2010.
In the U.S., Syngenta is facing lawsuits from farmers and shipping companies regarding Viptera genetically modified corn. The plaintiffs in nearly 30 states contend that Syngenta's introduction of Viptera drove down U.S. grain market prices, leading to financial harm, and that Syngenta acted irresponsibly by doing too little to enable shipping companies to export the grain to approved ports. Before Viptera's 2010 introduction Syngenta secured all U.S. and NCGA-recommended export approvals, but none from China. China had imported little to no U.S. grain prior to 2010, and at the time was not considered a major partner, which changed in 2010, when it dramatically increased U.S. grain imports. For three years, China imported U.S. Viptera grain without formal approval. In November 2013, Chinese officials destroyed a U.S. grain shipment containing Viptera grain and began rejecting all U.S. shipments with the GM grain. The same year, U.S. corn market prices dropped $4 per bushel, causing over $2.9 billion in losses, with just over half of that loss occurring prior to China's November rejection. China later approved the GM corn in 2014, but U.S. corn grain market prices have since not rebounded. Syngenta lost the first lawsuit to reach trial in Kansas on 23 June 2017, and was ordered to pay the farmers $217 million. However, Syngenta has stated it would appeal the verdict.
In 2022, the Federal Trade Commission announced that it is initiating litigation against Syngenta, challenging certain US-based discount programs extended to their respective customers. In January 2024, a federal judge ruled that both Corteva and Syngenta must face the FTC lawsuit. In December 2025, the Trump Administration and 12 US states asked a Federal Judge to expedite the process so the trial may proceed.
Paraquat and Parkinson's disease
In June 2021, Syngenta paid $187.5 million to settle an unknown number of cases in Illinois and California, implicating the company's Paraquat herbicide as a cause of Parkinson's disease.
In 2024, more than 5,000 Americans have active lawsuits against Syngenta, alleging ties between use of the paraquat herbicide product, Gramoxone, and the onset of Parkinson's disease. Syngenta denies any causal link between its product and Parkinson's disease. Syngenta took steps in April 2025 to resolve the majority of approximately 5,800 lawsuits pending in multidistrict litigation in federal court in Illinois. In addition, there were approximately 450 lawsuits pending in California state court and many more in state courts across the country.
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Internal documents from Syngenta, unsealed as part of court proceedings, showed a memo from the company's head of regulatory sciences, Lewis Smith, warning about the scientific consensus that paraquat was linked to Parkinson's disease.
In January 2026, Syngenta settled a lawsuit from a retired landscaper who had developed Parkinson's disease after decades of using Paraquat. The case was just about to go to trial in Philadelphia, Pennsylvania.
Controversies
In 2007, Syngenta came under scrutiny by the U.S. Securities and Exchange Commission. This was due to third-party sales of products in countries such as Iran, Cuba, North Korea, Sudan, and Syria.
In the past, Syngenta's crop protection products have also been the subject of repeated criticism. The company was accused of including the sale of highly toxic pesticides in its business model. In 2012, the company was therefore nominated for the "Public Eye Award", which denounces companies with questionable human rights practices. In 2023, the Arkansas attorney general Tim Griffin ordered Syngenta to sell land in the state under a prohibition against land sales to entities with "a connection to a country subject to the federal International Traffic in Arms Regulations."
Brazil
On 21 October 2007, a Brazilian peasant organization, the Landless Workers' Movement, led a group of landless farmers in an invasion of one of the company's seed research farms, in protest against genetically-engineered ("genetically modified") vegetables and in hopes of obtaining land for landless families to cultivate. After the invasion had begun, a team from NF Security arrived in a minibus and a fight with gunfire ensued. A trespasser and a security guard were killed, and some trespassers and other security guards were wounded.
The Brazilian police investigation, which concluded in November 2007, blamed the confrontation and death of the trespasser on nine employees and the owner of NF Security; the leader of MST was blamed for trespassing. The inquiry found that the invader was fatally shot in the abdomen and in the leg. The security guard was shot in the head. Eight others were injured, five of them invaders.
The Civil Court of Cascavel granted an order for the repossession of the site on 20 December 2007 and on 12 June 2008, the remaining MST members left the Santa Teresa site they had been occupying. On 14 October 2008, Syngenta donated the 123-hectare station to the Agronomy Institute of Paraná (IAPAR) for research into biodiversity, recovery of degraded areas and agriculture production systems, as well as environmental education programs.
In November 2015, Judge Pedro Ivo Moreiro, of the 1st Civil Court of Cascavel, ruled that Syngenta must pay compensation to the family of Valmir Mota de Oliveira ("Keno"), who was killed in the attack, and to Isabel Nascimento dos Santos who was injured. In his sentence the judge stated that "to refer to what happened as a confrontation is to close one's eyes to reality, since […] there is no doubt that, in truth, it was a massacre disguised as repossession of property". The version of events put forward by Syngenta was rejected by the Court. In May 2010, Syngenta was condemned by the IV Permanent People's Tribunal for human rights violations in Brazil.
Tyrone Hayes
There has been a long-running conflict between Syngenta and University of California at Berkeley biologist Tyrone Hayes.
In 2010, Syngenta forwarded an ethics complaint to the University of California Berkeley, complaining that Hayes had been sending harassing e-mails to Syngenta scientists. Legal counsel from the university responded that Hayes had acknowledged sending letters having "unprofessional and offensive" content, and that he had agreed not to use similar language in future communications.
According to an article in the 10 February 2014, issue of The New Yorker, Syngenta's public-relations team took steps to discredit Hayes, whose research is purported to suggest that the Syngenta-produced chemical atrazine was responsible for abnormal development of reproductive organs in frogs. The article states that the company paid third-party critics to write articles discrediting Hayes's work, planned to have his wife investigated, and planted hostile audience members at scientific talks given by Hayes.
During a 21 February 2014, interview conducted on Democracy Now, Hayes reiterated the claims. After the interview aired, Syngenta denied targeting Hayes or making any threats, calling those statements "uncorroborated and intentionally damaging" and demanding a retraction and public apology from Hayes and Democracy Now.
Response to Russian invasion of Ukraine
Syngenta continues to operate in Russia despite the ongoing invasion of Ukraine and international sanctions imposed on the Russian economy. The company remains a major player in the Russian agricultural sector, supplying pesticides and seeds to local farmers. It has been criticized for maintaining business-as-usual in the country, earning an "F" grade in a ranking of companies that have failed to exit or reduce their activities in Russia. It was condemned for prioritizing profits over ethics. Ukrainian President Volodymyr Zelenskyy has denounced companies that continue operating in Russia, stating that the Russian market is "flooded with blood." Syngenta has not only remained in Russia but has also announced price increases on its products, raising questions about whether it is exploiting the situation for financial gain. Critics argue that its continued operations strengthen Russia's agricultural industry, indirectly supporting the country’s war efforts. However, Syngenta also has maintained business as usual in Ukraine, taking similar or the same actions there.
