Waterhemp continues to be a problem in parts of northwest Iowa. There is a fair amount of waterhemp that survived the glyphosate and/or Flexstar applications in late June.
There is also a new crop of waterhemp that has germinated recently. That fact is surprising since it has been fairly dry in July for a lot of northwest Iowa.
There is not much that can be done to manage this waterhemp problem at this time of year. Herbicides like Cobra and Ultra Blazer can be used – they have a 45 and 50 day Pre Harvest Interval. However, they will at best – burn a few leaves off of the waterhemp and suppress it’s growth. And the crop oil type additives that make Cobra or Ultra Blazer more effective as a waterhemp killer – will add to the leaf burn on the soybean plants. So this is one thing that can be done this time of year, but it is not a real good option.
So if herbicide application is not a good option – what is left? I have heard a few comments on hiring a crew – or whomever they can get – to walk the beans. This may not be a real good option either, but many farmers are fairly motivated to do something with these waterhemp problem acres.
Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on July 31, 2015. The information contained within may not be the most current and accurate depending on when it is accessed.