When you can’t beat ’em, scream monopoly. That’s the vintage gambit now playing out in the farm business, with the encouragement of the Department of Justice.

At the first of a series of workshops this month, Attorney General Eric Holder, antitrust chief Christine Varney and Agriculture Secretary Tom Vilsack presided over a “forum” for farmers, activists and others to discuss competition in the agriculture industry. The occasion looked more like the Obama Administration’s latest dunk tank for business. “Recessions and long periods of reckless deregulation can foster practices that are anti-competitive and even illegal,” Mr. Holder warned in his speech.

Held in Ankeny, Iowa, the gathering occurred in the backyard of DuPont’s seed company, Pioneer Hi-Bred. DuPont/Pioneer has become an ally of the Justice Department’s resurrected antitrust posse. DuPont has filed an antitrust suit against Monsanto over its dominance of a sliver of the soybean market, and the company hopes Mr. Holder’s trustbusters will grant it success where the market has not.

The controversy involves a soybean-seed technology created and patented by Monsanto in 1996. Called Roundup Ready, the product became a favorite among farmers because the soybean it produces is resistant to weed killer. At first, DuPont aimed to challenge Monsanto directly, developing a product called Optimum GAT. When that failed as a stand-alone product, DuPont came up with plans to use it as a so-called stacked product-a seed that included both Monsanto and DuPont technologies.