his year a drought hit oat farmers just in time to shape oat production nearly in half in Canada, the world’s largest oat exporter. In the United States, one of the top consumers of the grain used in everything from oat milk to Cheerios to granola bars, the harvest will be the smallest ever.

That has sent oat futures, up 2.1% on Friday, to an all-time high of $6.36 a bushel in a year when global food pries have already hit a decade’s high.

That has hurt the share price of companies that produce oat-based products. General Mills (GIS), the maker of Cheerios, for example, has seen its stock price fall from $64.03 on June 4 to $61.70 at the close on October 11.

No stock has been hit harder, though, than oat-milk producer Oatly (OTLY). The stock, which went public on May 20, soared to hit $28.73 on June 6. Today the shares closed down another 3.08% at $14.15.

General Mills and Oatly have enough market place clout, probably, to secure the oat supplies they need. Oatly, for example, has signed contracts in the Baltics, and has forecasts that it will be able to increase production and sales as planned over the next year. In August the company predicted that revenue will grow by 64% in 2021. General Mills used its scale and long-standing relationships with growers to secure enough oats to maintain volume for Cheerios, which is celebrating its 80th anniversary this year.

What’s much less certain–and what’s behind the drop in stock prices–is what price companies such as Oatly and General Mills will have to pay for their oats. Neither of those companies is talking specifically about increases in the cost of oats or the need to raise prices.

Oatly, which is still losing money as it expands sales and production, reports third quarter earnings on November 15. General Mills doesn’t close its third quarter until November 30.

One added bit of uncertainty comes from the impact of the drought on other crops such as canola, flax, lentils, mustard, and durum wheat. Prices for those commodities are also steeply higher meaning that farmers have lots of alternatives for increasing planting next year.