Winter Rye Cover Crop Effect On Corn Seedling Pathogens.

Cover crops are an excellent management tool to improve the sustainability of agriculture.  Winter rye cover crops have been used successfully in Iowa corn-soybean rotations.  Unfortunately, winter rye cover crops occasionally reduce yields of the following corn crop.  We hypothesize that one potential cause of this corn yield decrease is that glyphosate-killed rye cover crops may be hosts for corn seedling root pathogens and the dying cover crops may pass those pathogens on to the following corn crop.  If environmental conditions are favorable for these pathogens to infect corn plants (cold and wet), then these pathogens might decrease yield in some years or fields. To test this idea, we began a series of pot studies in a controlled environment chamber. Preliminary experiments indicate that dying rye cover crop plants may pass on pathogens to germinating corn seedlings and increase infection of seedling roots under cold temperatures.  Corn seedlings following a rye cover crop had radicles with visible necrosis and were shorter than radicles of corn that did not follow rye.  Corn leaf height and dry weight of plants following rye were also less than the controls.  Additionally, roots of corn plants that followed rye had more fungal colonies develop than control plants when they were surface sterilized and places on selective media.  Thus, at least in controlled environment pot studies there is evidence of increased seedling root infections following cereal rye.