Control Weeds in May

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Look on any herbicide label and you’re bound to find the phrase, “Spray when weeds are actively growing”. That’s such a common sense statement but one often overlooked. If weeds are stressed because temperatures are too cold or too hot, or soil moisture is too wet or too dry, they will not absorb herbicides and control will be less than expected. May is a good month to consider control of many of our broadleaf weeds in pastures, fencerows and other areas.

Whenever I get calls for control options I always reach for the current copy of our K-State Chemical Weed Control guide. The guide is broken down into crop sections representing the major crops grow in Kansas. The first page or two in each section is devoted to a listing of herbicides that are labeled for each crop. They are broken down into preplant, preemerge, and postemerge so you know when to time your application. Each herbicide is given a rating for how effect is should be on a particular weed. Follow up pages will give a few comments about each herbicide with the range of product to apply per acre. There is also a special section that gives approximate retail costs of herbicides and another handy chart that lists the toxicity and the persistence in soils of each product. Collectively, the weed control guide will give you most of the information you need to make a herbicide decision.

Once you have settled on a product, or if you still have some question that are more specific, the best place to go is to read the actual herbicide label. I know that sounds about as fun as reading the phone book, but when it comes to herbicides, the label is the law. A resource I use to look up label information is an on line resource called Crop Data Management System or CDMS. Their web site at http://www.cdms.net will allow you to search for and look at any agricultural herbicide label. And with a little use you will be able to easily find mixing instructions, tank mix combinations, specific herbicide rates and other important details.

Another very good county resource is our county noxious weed department. They not only offer herbicides at a reduced cost, but the director, Jim Hoge, is a great source of technical expertise. Jim’s telephone number is 715-8358 and the Johnson County Government web site.

Written by Juju Wellemeyer