Due to the 2011 drought, there has been a large influx of hay into the Southern Great Plains. Within this hay, weeds - some not native to the region- have been inadvertently distributed into many pastures. Since the warm-season forages were often completely consumed during the drought, there is a need to control weeds (both native and introduced) to reduce their competition with warm-season forages. So what weeds are expected this summer and how can producers get the most control out of budgeted herbicide dollars? The best way to answer these questions is to (1) properly identify the weed, (2) identify a chemical labeled for its control and (3) apply the chemical at the proper stage of the weed's growth with a calibrated sprayer.
All weed control programs begin with proper identification of the weed in question. The only way to know the particular weeds that are present is by scouting individual pastures and identifying undesirable plants. Some of these weeds will be familiar; others will be new to the pasture. There are several different websites, including the Noble Research Institute's Plant Image Gallery, that are excellent resources for plant identification. In addition, local agricultural consultants or extension agents may be able to identify the weed from a photograph. Most of the time, identification is a quick and easy process, but sometimes it takes a sample of the weed and an identification book to figure out the genus and species.
Determining if a chemical can control a specific weed can be more of a challenge. Two handy publications are Pasture and Hay Field Weed Control for Texas and Pasture and Hay Field Weed Control for Oklahoma. Using tables and weed control data from state universities, a person can quickly determine which herbicide provides the best control of a particular weed. If the pastures are located outside of Texas or Oklahoma, contact that state's extension service and visit with them.
Always read and follow the label directions as they can change over time. The label will provide information on timing of the herbicide application. If the label states that the range is from emergence to a 6-inch height and the chemical is applied when the weed is 12 inches tall, one should not be surprised that the herbicide does not provide an adequate level of control.
The early application of 1 quart of 2,4-D amine per acre to control actively growing broadleaf weeds less than 6 inches tall is a good general recommendation. If the weeds exceed this height, choose another herbicide that is labeled for the weed. This inexpensive weed control option should remove all but the most difficult to control broadleaf weeds from the pasture. However, this recommendation will not fit all situations and must be evaluated on a pasture-by-pasture basis to determine if it fits the pasture and the ranch management system. Identify those weeds that remain and choose the best method of control if the weeds are numerous enough to cause economic injury.
This article only touches on a few basic items necessary for a good weed control program. Be aware of the plant species emerging over the spring and summer, and contact an agricultural consultant if additional management information is needed.