Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
A lot of thought needs to go into which cover crop species or mixtures to use, including what is the objective or issues being addressed with cover crops, what is the seeding rate, best seeding methods, etc. But often overlooked are what will it take to terminate the cover crop in the spring, and whether there could there be issues with the species in the rotation. Two species that merit consideration are hairy vetch and annual ryegrass. Both can be difficult to kill in the spring. Glyphosate alone is not very effective on hairy vetch. For annual ryegrass, glyphosate in the early spring may not provide complete control, and tankmixing other products with glyphosate can reduce control.
Both hairy vetch and annual ryegrass can be problems in small grains. Hairy vetch has hard seeds and not all the seeds will germinate right after seeding; with some germinating next spring or the following fall. In addition, if annual ryegrass or hairy vetch are terminated in the late spring, they may have produced viable seeds that can produce volunteer plants. Harmony Extra will not control either species. Hairy vetch needs to be treated with Starane Ultra, 2,4-D, dicamba or fall treatments of PowerFlex. Ryegrass will need to be treated with Axial or fall treatments of PowerFlex or Osprey. Note that annual ryegrass is very closely related to Italian ryegrass with both responding the same to herbicides.
So, before you plant cover crops, don’t only think of that they will do for you this year, but consider how the species match with your rotations.