One of the more troublesome weeds, particularly of hay fields, showing up this time of year is foxtail. There are three warm season annual species of foxtails we can see in Northeast Kansas: green, yellow and giant.
Our best bet for combating foxtail infestations is a healthy stand of our desired forage. It often starts with an appropriate fertility/grazing/haying program for cool season forage systems to help them compete against the foxtail that must get a start from seed each season (well after the brome or fescue has already started growing). Unfortunately, too many years of late season heat or drought or armyworm infestation – or all three – have thinned stands, allowing the warm season foxtails to germinate and grow with plenty of space to get a foothold.
Mowing can help, but it will likely have to be done multiple times. Foxtail plants thrive in our warm summer weather and even when cut off will likely try to put up a head again, often lower in height than it was the first time. Even if we could cut low enough to get the lowest of the seed heads, we could be doing damage to the recovering cool season grass as we did so.
One of the more common questions centers around herbicide control programs. A cross reference of labels for control of foxtail in brome (www.cdms.net – Advanced Search option) yielded three active ingredients: Glyphosate, Pendimethalin and Quinclorac. Glyphosate is non-selective, meaning it’s going to indiscriminately control anything green it’s applied to and is not a great option in most pastures or hay fields unless you can manage spot treatments well.
Pendimethalin has received some testing attention in Kansas by former NE Area Extension Agronomist Dr. Stu Duncan. He tested three different products, with the Pendimethalin product Prowl H2O (applied in early spring) showing the best combination of control with minimal crop injury. Unfortunately, even those applications did not reduce late-summer foxtail pressure even after showing apparent suppression well into the growing season.
Herbicide applications for foxtail control aren’t without issues. In addition to the potential for crop injury noted in his study (see the entire study results online at https://eupdate.agronomy.ksu.edu/eu_article_prep.php?article_id=2773), be sure and read product labels closely before doing applications. Seedling grass injury could occur if seeding were to occur in these areas too close to the time of herbicide application.
When these pre-emergence products do work, they could leave “open space” where foxtail has been prevalent in previous years until desirable forages can fill in. Other broadleaf weeds could fill in as well. Careful management will be needed to prevent new plants from getting a start next year.
There is no silver bullet – but there are options. For the best results, implement a good prevention program whenever possible. If that isn’t enough, and foxtail continues to be an issue, other options like mowing or maybe even herbicide control programs may need to be considered.