THE FLORIDA CATTLEMAN AND LIVESTOCK JOURNAL
Weed Management in Limpograss
Brent Sellers and Jay Ferrell
There appears to be some confusion when it comes to weed control in limpograss. First, there are several names that we use for limpograss, including Hemarthria, limpograss, and Floralta. While none of these are incorrect, it is a common misconception that these names refer to different forages. It is not necessary to call limpograss by a certain name, -only to realize that all three names refer to the same forage grass. Second, new herbicides have recently been introduced into the pasture market; the safety of these herbicides on limpograss is dependent upon both time of year and stage of growth. This article is intended to help reduce the amount of confusion in the herbicide recommendations for weed control in limpograss pastures and hayfields.
Weed control at establishment.
There are only two herbicides that can be used for weed control at establishment. The most troublesome weeds during the establishment period are the annual and perennial sedges (commonly called watergrass, etc.). The most effective and safe herbicide treatment for control of sedges is 1.5 – 2 pt/acre dicamba (Banvel, etc.) applied 7 to 10 days after planting. If tropical soda apple is an issue in newly planted limpograss, apply Milestone at 3 oz/acre. Applying 2,4-D or products that contain 2,4-D is not recommended for newly established limpograss as it may cause substantial injury and lengthen the amount of time before the pasture is fully established.
Weed control in established limpograss.
Dicamba has been the long-standing standard herbicide for weed control in limpograss. Because 2,4-D and other commonly used herbicides were tested at establishment, it was believed that these products would kill limpograss. However, many of the herbicides that are available in the pasture market can be used for weed control in limpograss, but the timing of application becomes a factor. In general, the use of 2,4-D or products containing 2,4-D should not be applied between April and November unless injury can be tolerated. Below are the most commonly recommended herbicides for use in limpograss for weed control including information on limpograss tolerance.
Dicamba (Banvel, etc.). This is the standard herbicide for weed control in limpograss pastures. The advantages of dicamba include good weed control, and good forage safety regardless of application timing. Most weeds are controlled with 2 pt/acre, but 3 pt/acre may be needed for larger dogfennel. If dogfennel are larger than 3 feet tall, dicamba will not provide adequate control.
Milestone (aminopyralid). Milestone can be used year-round on limpograss, but is recommended only when tropical soda apple has become a problem in limpograss pastures. Use 3 oz/acre at establishment and 5 oz/acre in established limpograss. The low recommended rate for tropical soda apple control at establishment is related to the size of tropical soda apple plants; small plants require less herbicide for effective control.
2,4-D (Weedar, 2,4-D Amine, etc.). This herbicide has received a lot of negative attention with regards to its use in limpograss. In the past it was thought that 2,4-D would kill limpograss. The only time that 2,4-D kills limpograss is when it is applied during the establishment period. There is a time period, however, when 2,4-D can cause severe injury of established limpograss. During the summer growing season when temperatures and relative humidity are high, 2,4-D amine almost always causes severe injury Regrowth does occur, but it takes some time. If this herbicide is applied during the cooler seasons (November through April), the amount of injury observed in limpograss is greatly reduced. Our research has shown that 4 pt/acre of 2,4-D in the early spring results in little to no limpograss injury.
GrazonNext (aminopyralid + 2,4-D). This is a relatively new name for a herbicide that has been available the past few years. Wherever you read the name ForeFront in our herbicide recommendations, you should replace it with GrazonNext. Because it contains 2,4-D some caution is required when using this product for weed control in limpograss. GrazonNext can be safely applied to limpograss from November through April. May through October applications may result in severe limpograss injury.
Cleanwave (aminopyralid + fluroxypyr). This herbicide is a common tank-mix partner with GrazonNext to increase dogfennel control. Because it provides no control of pigweed (careless weed), it is seldom recommended alone. . Although this herbicide does not contain 2,4-D, substantial injury can occur when applied during the summer months and during active limpograss growth. Therefore, it is best to apply Cleanwave with GrazonNext or 2,4-D from November through April.
Chaparral (aminopyralid + metsulfuron). Chaparral is a new herbicide that was not widely available in 2009. The application rates for this herbicide range from 2.0 to 3.3 oz/acre. Good control of winter annual weeds and thistles can be achieved at a rate of 2.0 oz/acre. Bahiagrass can be suppressed with this herbicide when applied at 3.0 oz/acre during the summer rainy season. The drawback to Chaparral is that it will not provide control of dogfennel; But, expect good to excellent control of tropical soda apple, pigweed and blackberry. We have not examined the limpograss tolerances of this herbicide during the summer growing season. As a result, caution should be exercised when using this product for weed control in limpograss.
Herbicide tolerance in limpograss is tricky, but the easiest way to remember when herbicides can be safely applied in limpograss is to stop using products containing 2,4-D, triclopyr or fluroxypyr after tax day (April 15). If herbicides other than Banvel or Milestone are applied after tax day, the chance of herbicide injury in limpograss increases dramatically. Applications of herbicides containing 2,4-D can resume with reductions in limpograss injury as early as November. Table 1 illustrates when herbicides can be used for weed control in limpograss.
The key to determining limpograss response to herbicides is to understand the maturity and health of the stand. A newly established pasture will not have a well established root system or the energy reserves to overcome the stress of a herbicide application. As a result, a new stand is more susceptible to herbicides than mature stands. Similarly, if an established limpograss pasture was recently grazed or cut for hay and the regowth is lush and tender, some herbicide injury should be expected. This is because the pasture is under tremendous stress as it attempts to regrow and the added stress of a herbicide application is simply too much to handle. As a rule of thumb, a stand that is at least 6 weeks old (6 weeks since last graze or cutting), will show minimal injury since the plant has had sufficient time to reestablish its energy reserves.
Traditionally we have been “locked in” to using very few herbicides since it was thought that almost all pasture herbicides were too injurious to limpograss. This is simply not the case. There are many excellent herbicide choices; some simply require extra attention to the environmental conditions and health of the pasture. If the concepts discussed in this article are considered and given due attention, weed control can greatly improve along with the quality of grazed and stored limpograss with minimal injury.
Table 1. Limpograss tolerance to herbicides. Herbicides are safe to apply when a particular month has a check mark. If there is no check mark, injury from the respective herbicide may occur.