Washington Attorney General Bob Ferguson on Dec. 23 joined a federal lawsuit alleging pesticide makers Syngenta and Corteva engage in antitrust practices that drive up prices farmers pay for crop-protection products.

The suit claims Syngenta and Corteva squash competition by giving rebates to a handful of large pesticide distributors who favor the companies’ products over lower-priced generic competitors.

Syngenta and Corteva have moved to dismiss the lawsuit, filed in the U.S. District Court for Middle North Carolina by the Federal Trade Commission and 12 state attorneys general.

Syngenta argued in a brief Dec. 22 that the rebates reward customer loyalty and that the suit was premised on the “remarkable proposition” that cutting prices was anticompetitive.

The FTC and 10 states, including Oregon and California, originally filed the suit in September.  The suit was amended to add Washington and Tennessee as plaintiffs.

The bipartisan group of attorneys general includes eight Democrats, including from Colorado, Illinois, Iowa, Minnesota and Wisconsin, and four Republicans from Indiana, Nebraska, Tennessee and Texas.

The suit was filed after a three-year investigation by the FTC. Key information collected during the probe, such as financial figures and comments from company emails, remain undisclosed.

The suit alleges Syngenta and Corteva give rebates to prop up sales for products with active ingredients that they no longer have exclusive control over.

Distributors allegedly received “substantial” payments for selling a certain percentage of “off-patent” Syngenta or Cortreva products rather than low-cost generic alternatives.

Since only seven distributors control 90% of the pesticides sold to farmers, the loyalty program was an efficient way to maintain a near monopoly, the suit claims.

The lump-sum, end-of-the-year rebates were complex and lacked transparency, making it more likely distributors pocketed the money rather than pass along the discount to farmers, the suit alleges.

“Substantially all leading distributers” participated in the loyalty programs, according to the suit. Manufactures of generic alternatives were allegedly discouraged from making low-cost products that would have saved farmers money.

Syngenta Group, based in Switzerland and with North American headquarters in Greensboro, North Carolina, defended the program as a legitimate way to compete with generic products.

Corteva made similar arguments in a separate motion to dismiss the suit. “A rebate is simply a discount,” according to the company, based in in Indianapolis, Indiana.

Syngenta is accused of using rebates to prop up the sales for products with three off-patent active ingredients: azoxystrobion, a broad-spectrum fungicide; mestotrione, a widely used corn herbicide; and metolachlor, a herbicide used on a wide variety of crops.

Corteva is also accused of seeking to shield from competition products with three off-patent active ingrdients: rimsulfuron, a herbicide used on many crops; oxamyl, an insecticide and nematicide primarily used on cotton and potatoes; and acetochlor, a herbicide primarily used on corn.

“When farmers are paying more for their crops, it impacts everyone,” Ferguson said in a statement. “The law demands fair competition. I will stand up to corporate greed.”