[Image: pasture]With the advent of more frequent rains, our pastures are growing better than they have so far this summer. There are still problems, however.
Army worms are present in pastures every year. This year I have received several calls about infestations. The army worm is the larvae or immature stage of a moth. The moth lays eggs on the most immature or most nutritious grass she can find. The eggs hatch and the larvae (worms) begin to feed. Army worms can cause significant loss when they are present in large numbers. They are most destructive to newly planted grasses. Their feeding can cause stand loss on forage grasses that haven’t developed sufficient root and stolon (runner) systems. On established pastures and hay meadows they just eat the grass that otherwise would be available for livestock. An indication of the presence of army worms often is large numbers of cattle egrets feeding in a pasture. Cattle egrets seem to prefer army worms as a food source.
The threshold for treating pastures for army worms is one or more worms per square foot. There are several insecticides labeled for control including: Carbaryl, Lannate, Methyl parathion and Tracer. Be sure to follow the pre-harvest intervals and grazing restrictions when applying any of these insecticides. If the army worms are infesting a hay meadow that is ready to harvest, I suggest harvesting the hay. The worms will crawl away and seek other green grass. If they persist in the harvested meadow, treat the area after the harvest and the bales are removed. This should allow for the pre-harvest interval.
Smut grass is a real problem weed in pastures in our area. Sporobolus poiretii is the name that botanists know it by. Livestock producers use other more colorful, less complementary names for it when it invades their pastures. Smut grass is a perennial plant, meaning that it re-grows from the roots each year. It is an erect, bunch-forming grass with narrow, pointed leaves that are rough to the touch. These bunches or clumps can reach 3 feet in height. It gets the name “smut grass” from the seeds that it produces. These seeds are borne on a stem and are often infected with an ergot fungus that turns the seeds black in color. These tiny, black seeds give the impression that the stem is covered with “smut.”
The seeds are one characteristic that makes the plant so much of a problem. It produces many thousands of them. They will stick to animals and humans that brush against the plant and are transported from one part of the pasture to the other.
The rough leaves are also a problem. Because of this and other characteristics, livestock will not eat the plant after it reaches any height at all. It grows very fast in the spring. Like all plants, smut grass has to compete with other plants for sunlight, water, nutrients and space. If the livestock eat the other plants in the pasture and leave the smut grass alone, it has an advantage and will continue to grow and spread. This selective grazing is most evident with animals that feed close to the soil surface such as sheep and horses. Cattle will also graze pasture “into th -ground” if they are short on forage due to drought or overstocking. Smut grass always seems to be worse in pastures with more livestock than the grass can support. Even though this may be a temporary situation, once the smut grass gets established it will continue to spread even if the pasture conditions improve or the stocking rate is corrected.
How do you control this weed? Not very easily or well, I am afraid. Because it is a perennial plant, smut grass does not respond well to mowing. It will simply produce more tillers, re-grow and the clump will become larger. There are limited herbicides available for its control. Velpar is labeled for smut grass control. But Velpar is not inexpensive. It also must be applied correctly and under the right conditions to effectively control the smut grass. Most of the herbicidal action of the Velpar is due to root uptake by the smut grass. For proper root uptake, there must be adequate soil moisture at the time of application. It is also beneficial to receive a light to moderate rain within a few days of the Velpar application. The rain will move the herbicide into the root zone where it will be absorbed by the roots. Velpar also is most effective on rapidly growing smut grass. If the smut grass is stressed by drought or other weather conditions, the herbicide will be less effective. Velpar will also injure the Bermuda grass or other summer forages that you want to grow. It has very strict restrictions on grazing or haying after its application. It requires several weeks before the pasture can be grazed or cut for hay or another forage crop can be planted. Some producers have had very favorable results with Velpar. Others haven’t. I believe that the main reason for this inconsistence is due to the weather conditions at the time of its application and immediately after application. I told you that smut grass control wasn’t simple or easy
Roundup (or other glyphosate herbicides) will kill smut grass. Unfortunately, they will also kill the desirable grasses that are growing in the pasture. If you “spot spray” the smut grass clumps with glyphosate, you will kill the entire spot, leaving a bare area. Often other weeds will emerge in the bare spot, and you have only traded one weed for another.
One cultural practice, plowing, can be effective. Again, the environmental conditions must be right for plowing to work well. If the smut grass is plowed during a period of dry weather, the roots will desiccate and the clump will die. The soil must be dry, or the smut grass clump will merely re-root and begin to grow again. However, producers have effectively reduced their smut grass problem by plowing, uprooting the clumps and drying them out in late season. If this can be accomplished in the late summer or early fall, ryegrass can be planted into the pasture. The ryegrass will emerge, grow through the winter, provide grazing for livestock and prevent the smut grass from emerging in the early spring. Ryegrass is very competitive with other grasses in the spring. Until it matures in May or June, no other grasses will emerge. If properly timed and with cooperative weather, the fall plowing-ryegrass establishment method is very effective and economical.
Smut grass is a very costly pasture weed, but with proper technique and good luck, it can be managed over time.