Time to Spray Cool-Season Grasses
in native warm-season grass fields dominated by big bluestem and Indian grass. I only recommend this in fields dominated by native grasses with very few desirable forbs since non-selective herbicides will also damage or kill some of the native grass. It has been my experience that most of the native grass comes back just fine. By stunting the native grass you have created more bare ground for quail. Again, do not use non-selective herbicides if there's a lot of wildflowers in the field.
In Missouri, don't spray non-selective herbicides until mid to late April or when the grass is at least 6 inches tall. Try to finish all spraying by mid May. You only have a short window in the spring before the grass gets too tall or other desirable plants start to grow. Another key to spraying in the spring is to watch the long-term weather forecast. You might not get a good kill if you spray on a warm, sunny day that is followed by a week-long cold snap! Make sure you have a good long-term forecast with lots of warm weather.
To Spray or Not To Spray
Have you ever burned a warm-season grass field in the winter to find out the next spring the field was infested with cool-season grasses? This is a tough management decision for biologists and landowners. Should I spray the field in the spring or wait until fall? The correct answer depends on what's in the field.
If there are a lot of wildflowers you might consider spraying a grass selective herbicide in the spring. Another option is to wait until the fall and spray the area with a non-selective herbicide. You will have to mow, hay or graze the field in the summer to prepare the area for a herbicide application. The new growth will not carry a fire.
If there are only big native grasses and not a lot of wildflowers, go ahead and spray it with a non-selective herbicide in the spring. The reasons I'd spray the field in the spring are that you have the field already prepared for a treatment and you will prevent the cool-season grass from setting seed. You can always come back in the fall and spray the places you missed, but at least you have taken care of most of the intruding cool-season grasses.
Scout it Out!
Take the time each spring and fall to scout for big patches of cool-season grasses or other unwanted plants. Mark the locations on a map and comeback and spray these areas at the appropriate time. Spot treatments will help maintain quality habitat and prevent whole-field renovations down the road. An ounce of prevention saves money, time and future headaches.
Converting whole fields to native grasses
Biologists can debate some pretty silly things sometimes. Like when to spray a cool-season grass field that will eventually be converted to native grasses and wildflowers. Some say spray in the fall and again in the spring. Others say spray the field in the spring, summer and fall for a dormant seeding. Both work and have there place. In most cases I prefer multiple treatments during the summer and fall versus the traditional fall and spring treatments. If feasible I even recommend converting the cool-season pasture to row crops for one or two years. The intensive farming will take care of most of the weeds and unwanted grass and leave you with a beautiful seed bed. Since every farm and field is different I recommend working with a resource professional to determine which treatment schedule works best for your property.
Habitat is the Key!