Sicklepod is one of the most difficult weeds to control in soybeans. Although less competitive on a per-plant basis than many other common annual broadleaf weeds, heavy infestations can reduce soybean yields 60 to 70 percent or more. In addition, a price dockage may occur because of foreign matter (sicklepod seed) in the harvested product.
Several herbicides are effective on sicklepod if used properly (Tables 1, 2, and 3). In many situations, two herbicide applications (preplant incorporated or preemergence followed by postemergence) may be necessary for acceptable control of moderate to heavy infestations.
Sicklepod control in narrow-row soybeans. There are numerous benefits to be obtained from planting soybeans in narrow rows. Adequate sicklepod control can often be obtained in narrow-row soybeans. However, where sicklepod is a major problem and inadequate control has been achieved in narrow-row soybeans in previous years, you may want to consider planting in rows wide enough to allow for cultivation and postemergence-directed herbicide applications (see “Sicklepod Control in Wide-Row Soybeans”).
Herbicide options for at-planting application to control sicklepod include the following: (1) flumetsulam-containing products (Broadstrike + Dual and Broadstrike + Treflan); (2) imazaquin-containing products (Scepter, Squadron, and Tri-Scept); and (3) metribuzin-containing products (Canopy, Lexone, Salute, Sencor, and Turbo). Flumetsulam- or metribuzin-containing products tend to be more effective than imazaquin-containing products (see Tables 1 and 2). Other weeds expected to be problems and rotational plans (see Table 14) should be considered when deciding among these herbicide options.
If additional control is needed after applying one of the aforementioned herbicides, a postemergence application of Classic could be considered. If an imazaquin-containing product was applied at planting, a postemergence application of Scepter could also be considered if needed.
Research in North Carolina has shown that sicklepod control with a properly timed postemergence application of Classic is usually as good as the control attained with a soil-applied herbicide followed by Classic. However, relying entirely upon postemergence herbicides increases your risk. Before deciding to forgo soil- applied herbicides, consider whether or not you have sufficient equipment and labor to treat the sicklepod postemergence in a timely manner. Timing of application of Classic is critical for good results. Best results will be obtained when the sicklepod is 1 to 3 inches tall and has one or two true leaves.
Sicklepod control in narrow-row soybeans is highly dependent upon the crop shading out later-emerging weeds. Uniform stands and vigorously growing soybeans that quickly shade the ground are essential for sicklepod control in narrow-row soybeans.
Sicklepod control in wide-row soybeans. Planting soybeans in wide rows may be less risky than planting in narrow rows where sicklepod is a major problem. Planting soybeans in wide rows provides more options for sicklepod control. Planting in wide rows makes it possible to cultivate and to make postemergence- directed herbicide applications. Both of these practices have been shown to be effective and cost-efficient components of a sicklepod management program.
To control sicklepod in wide-row soybeans, you can apply a flumetsulam-, imazaquin-, or metribuzin-containing product at planting and cultivate. If additional control is needed, a postemergence application of Classic followed by cultivation is an effective program.
Either a soil-applied herbicide followed by cultivation or Classic applied postemergence followed by cultivation will give adequate early-season control of sicklepod. If the soybean canopy does not close relatively quickly, however, later-emerging sicklepod can become a problem. These later-emerging sicklepod have little impact on soybean yield but can lead to a dockage for foreign matter and can produce numerous seed to further infest the field. These later-emerging weeds can be controlled well with a postemergence-directed application of Lorox plus 2,4-DB or Sencor plus 2,4-DB.
Excellent season-long sicklepod control can be obtained with any of the soil- applied herbicides discussed previously or with Classic applied postemergence followed by cultivation and a postemergence-directed herbicide application. In addition, the postemergence-directed herbicides control essentially all other broadleaf weeds and are effective on small grasses.