Investors like strong margins and high barriers to entry when looking for quality stocks. They don't like the word anticompetitive, though.

Caterpillar, Deere, and other agriculture stocks fell Wednesday after the federal government launched a public inquiry into the farm equipment and distribution industry.

The Federal Trade Commission and the Department of Agriculture said Wednesday they are requesting information from the public "regarding issues affecting agricultural equipment manufacturing and distribution markets, including potential anticompetitive conduct."

The inquiry follows a couple of agriculture-related FTC settlements this year. Crop chemical maker Corteva agreed to dismantle a loyalty program. Deere made it easier for farmers to repair their own products.

The announcement hit Caterpillar stock the hardest, but it shouldn't have. The company doesn't actually have a lot of agriculture business.

Still, Caterpillar dropped 5.9% to $812.73, making it the session's worst performer in the Dow Jones Industrial Average and one of the worst in the S&P 500.

Shares of Deere, which relies much more heavily on farmers' businesses, fell 3.3% to $660.17 in late trading Wednesday, while shares of peers AGCO and CNH were both down more than 6%.

Caterpillar and Deere didn't immediately respond to a request to comment.

Shares of CNH dealer Titan Machinery and Cat dealer Finning were both down almost 5%. Shares of fertilizer supplier Mosaic dropped 4.6%, while crop chemical maker FMC's shares were down 0.9%. Corteva shares rose 3.6%, but KeyBanc upgraded the stock on Tuesday evening.

In short, the entire agricultural value chain was affected.

"Today's announcement is an industry-wide request for information -- not a new company-specific lawsuit or finding of any wrongdoing," Baird analyst Mig Dobre wrote Wednesday. "We view the news as largely immaterial, though it may create a near-term incremental overhang due to added uncertainty. This is an information-gathering exercise, not a new enforcement action."

It might be immaterial, but investors hate uncertainty.

The inquiry calls for information on business models, contract terms, and other issues that might affect market pricing. It aims to address "the growing number of complaints received by USDA that farmers across the country face other barriers to acquiring agricultural equipment and the services required to keep equipment operating," according to the release.

Comments are due by December, with no timetable for additional actions or remedies.

Investors might fear that any actions could slow higher-margin software growth in the agricultural sector. Deere wants recurring software-type sales to be 10% of revenue by the end of the decade.

The ramifications for Caterpillar, however, should be small. It has a much bigger presence in the construction, mining, and power generation industries than in agriculture.

That idea didn't help much in Wednesday trading, though.