For Release October 13, 1998

Weedy Grasses

AGRI-VIEWS
by Chuck Otte, County Extension Agent

Many of you have been noticing that there is a lot of crabgrass and/or foxtail in the brome fields and bromegrass waterways this fall. I know that many of you have been noticing because many of you have been calling me about it wanting to know what to do!

Crabgrass, foxtail and several other summer annual weedy grasses are very opportunistic, can be very aggressive and have very specific needs before they will germinate and grow. Any healthy stand of perennial grass, either cool season or warm season, will not be bothered, in the long run, by these summer annual weedy grasses IF the grass is being properly managed. If you had a problem this year with these grasses, but haven’t noticed them in the past, then you are probably the victim of unusual weather conditions. If you have been having this problem for several years and it is just getting worse, then there is a management problem that we need to address.

The first question that many producers are asking is, "What can I spray with to stop the crabgrass/foxtail?" In short, nothing! There are no products labeled for controlling or preventing crabgrass or foxtail in bromegrass. Would some of the crabgrass preventers for lawns work? They probably would BUT it is an illegal off label use, it would be illegal to feed the hay to cattle or graze the pasture, and it would be prohibitively expensive!

The foxtail and crabgrass both need bare soil and warm temperatures to germinate. If there is shade the seeds won’t germinate. When we normally expect these grasses to germinate, April and May, bromegrass should be growing rapidly and will easily shade the soil surface. But those grass seeds can lay dormant and wait for a better opportunity. If something happens so that there is bare soil for an extended period those grass seeds can germinate as late as August and still produce lots of growth and seed.

This year we had weather of all extremes occurring during the growing season. Some of the bromegrass was harvested a little bit late. Then it turned off hot and dry and most of the bromegrass experienced no post harvest regrowth. In late July we had two weeks of rainy weather. This started the bromegrass growing, but it also got the crabgrass and foxtail started and those grasses outgrew the bromegrass. Now those summer annual weedy grasses are dying down and will be gone with the first frost but oh look at all the seed that was produced.

It will be critical, over the next twelve months, to manage this bromegrass very carefully. First of all there needs to be a good application of fertilizer this fall. It would be best to soil test first, but in absence of that a good rule of thumb would be 100 pounds of nitrogen, 40 pounds of phosphorus and 20 pounds of sulfur per acre. If you are haying the brome next year make sure that you cut the hay between early heading and full bloom, usually the latter half of May. Do not cut earlier than early heading and make sure you leave at least 4 inches of stubble.

If you are grazing, the stocking rate needs to be such that there is at least 4 inches of stubble at all times. If the cattle are grazing it down to table top smoothness then problems will occur. As tempting as it is sometimes you should not try to hay and graze the same stand of brome the same year. If you have native pasture then stock the brome heavier in the spring and move the cattle on to the native by late May or early June. If you are stocking for the entire season then lower rates are necessary to provide forage through the summer. At some point the brome stand needs to have a rest and a chance to regrow. You can not continuously graze brome. It will thin out and become invaded by undesirable weeds. For more information on managing brome grass stop by the Extension Office and pick up our Extension bulletin on smooth brome production and utilization.

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