Avoid Making Cover Crops a Pest


By Travis Legleiter, Extension Weed Scientist

The use of cover crops in Kentucky is on the rise with more farmers looking to gain an edge wherever they can.   Cover crops have many benefits including keeping soils in place over winter, improving soil quality, and in some cases suppression of winter annual weeds.  Although, like all agricultural practices there can be drawbacks if a cover crop is not managed properly.  As we quickly approach the time to plant cover crops let’s look at how to gain the benefits of cover crops and avoiding the situation of a cover crop becoming a pest or introducing a pest.

Usually one of the first considerations when purchasing seed or planning a cover crop is the selection of species.  The use of annual ryegrass as a cover crop is highly touted for its underground biomass system, ability to grow in a multitude of growing conditions, and rapid establishment and growth.  Farmers should be aware though, that annual ryegrass can also become a weed and the attributes that make it a good cover crop also make it an excellent weed.  Annual ryegrass can be very difficult to terminate in the spring and a farmer must be knowledgeable of how to properly terminate annual ryegrass.  Annual ryegrass should only be grown by experienced cover crop growers and should be avoided by wheat producers as ryegrass is a major pest in wheat. 

Other considerations when planning your cover crop is whether you are going to plant a single species, multiple species, and where you are going to buy the seed.  Unlike our major commodity crops that are supplied by a handful of companies with stringent regulation on seed quality, you can buy cover crops from a variety of sources.  Cover crop seed can be purchased from a cover crop dealer, your local feed and seed store, or even the internet if you so choose.  With so many choices of cover crop species, seed mixes, and vendors the assurance of quality of that seed is not guaranteed.  The one seed quality that is of particular concern is contamination of weed seed.    Purchasing seed that has not been screened or tested for the presence of weed seed can lead to a situation of introducing a new pest to your field and/or neighborhood.  For example, the state of Iowa encountered an invasions of Palmer amaranth last year due to conservation reserve program seed mixtures that were contaminated with Palmer amaranth seed.  The good intentions of cover crops will be quickly nullified if a new major pest is introduced.   To assure that you are not introducing a new weed, buy seed that has been tested for the presence of weed seed and has the documentation to prove it.  When purchases a premix of species make sure that it is known that all species in the mix have been screened for weed seed.   A little bit of homework by the farmer now to assure he is purchasing clean seed will help avoid future pest problems, while capturing the benefits of cover crops.