Pay more, get less. That's generally not a very good business model, and it's the reason Monsanto (NYSE: MON) is down 12% since Friday.

Investors have become increasingly worried about Monsanto's SmartStax corn, which combines eight different traits to protect against bugs and make them resistant to herbicides used to kill weeds. Monsato sells SmartStax, which was developed with Dow Chemical (NYSE: DOW), at a premium to its older corn seeds that only sport a couple of traits because SmartStax is supposed to produce higher yields. The increased production should, in theory, pay for the increased seed price and then some.

So far that theory isn't holding up. With about 10% of the corn harvested, the SmartStax is actually trailing the production of the older seeds.

Let's take a step back before we declare SmartStax a bust and run out and buy competitors DuPont (NYSE: DD) and Syngenta (NYSE: SYT), and maybe some fertilizer producers such as Agrium (NYSE: AGU), Mosaic (NYSE: MOS), and PotashCorp (NYSE: POT) since the farmers obviously need a boost in yield. The sample size is still relatively small, and the yield comparisons are going to be somewhat dependent on the older seeds being attacked by pests. The corn harvested in other parts of the country later in the season may have better results.

And one season may not be enough to see the results. In a good year, the SmartStax might not live up to the hype, but it's kind of like buying crop insurance in case the bugs do get to the crops.

Will farmers buy my argument, which I'm guessing is the same one Monsanto will make? In the long run, they probably will, but Monsanto may need to discount the seeds for a few seasons until farmers are convinced SmartStax is worth the money.

Considering that Monsanto is counting on SmartStax to be a growth driver now that RoundUp is all dried up, a cut in revenue is going to hurt. Long-term investors will likely be OK, but anyone looking for a quick buck shouldn't expect Monsanto to turn around quickly.

Jeff Fischer decided one stock wasn't enough. He recommended an ETF in today's buy opportunity.

Monsanto is a Motley Fool Inside Value pick. Syngenta is a Motley Fool Global Gains selection. Motley Fool Optionshas recommended a synthetic long position on Monsanto. Try any of our Foolish newsletter services free for 30 days.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.

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