There have been some surprises this spring with rye showing up in fields when there was no rye planted previously, at least not intentionally. I figured it would be worthwhile to briefly discuss seed purity standards and control options.
First we have to make a distinction between PVP protected varieties and varieties that are, or are no longer, protected under PVP. If a variety is protected under Title V of the Plant Variety Protection Act, certification of the seed is required. Certification standards for the maximum number of seed of the other crops are 5, 10, and 30 seeds per 10 lbs. of seed for foundation, registered and certified classes of seed, respectively. That is roughly equivalent to 0.004%, 0.008% and 0.024% seed of other crop species in a seed lot of wheat, barley, or oats. The same standards apply to all varieties sold as certified seed - whether PVP protected or not.
If the grain you buy is not certified but still is intended to be used as seed, Minnesota’s seed law requires that such seed is properly and truthfully labeled. The statute considers a seed lot with less than 5% of another species a single species rather than a mixture as long as the percentage of other crop species is accurately stated on the label. These requirements are consistent with those of neighboring states and the Federal Seed Act.
A common misconception is that seed used for cover crop does not need to be certified and or labeled as such (i.e. is exempt from the rules and regulations of the applicable statutes) as there is no intention to harvest the crop for grain. If the variety in question is protected under PVP, certification is a requirement. If the variety is not protected under PVP, then proper labeling, including the % of other crop species, is still required.
Thus buying seed with up to 5.0% rye seed can be perfectly legal if the variety is not PVP protected and the label stated that the seed lot contained 4.99% other crop seed. Unfortunately that may now have created some management issues as rye survives even Minnesota’s harshest winters.
Removing rye from the small grains using a selective herbicide is not an option. This means that you’ll likely have rye, and possibly some ergot in your harvested wheat, barley or oats. A Kwik Kleen grain cleaner and/or gravity table are really your only options to remove rye and ergot from harvested grain. This should work well for barley and oats, but will only be partially effective in wheat.
In the future ask your seed supplier for purity and germination information about the seed you are buying. Cutting corners and planting the cheapest seed available may be more expensive in the long run. The Minnesota Crop Improvement Association has two PDF fact sheets available that also discuss the options and pointers on cover crops. You can find those recources here and here.