Prickly Sida Distribution and Biology
- Prickly sida (teaweed) is distributed throughout much of the temperate regions of the eastern two-thirds of the United States.
- Plants typically emerge in the field from April through September. Seed germination is promoted with high temperatures and enhanced when seeds are subjected to wet-dry cycles.
- Although prickly sida is not very competitive with soybeans, it has been shown to reduce yields by 5 to 10 percent when emerging at a density of 20 plants per square foot. Individual prickly sida plants can produce 1,000 seeds per plant.
- Prickly sida, which can grow up to 3 feet in height, can be identified by its relatively small, simple leaves, which are oval in shape with toothed leaf margins, alternately arranged on occasionally branched stems. The flowers are pale yellow with five petals. In the early vegetative growth stages, prickly sida might resemble hophornbeam copperleaf.
Herbicide Resistance in Prickly Sida
Prickly sida with resistance to imazaquin (a Group 2 ALS-inhibiting herbicide) was reported in Georgia in 1993.
Management of Prickly Sida in Soybeans
- Consider cultural practices. Cultural practices, such as the ones listed below, can help make soybeans more competitive with prickly sida and improve the consistency of any herbicide program.
- These practices include altering planting date relative to weed emergence, planting soybeans in narrow rows and using higher seeding rates for greater crop competition.
- Control existing weeds at planting. As a warm-season plant, prickly sida often does not emerge until after full-season soybeans have been planted. Burndown applications of glyphosate, glufosinate or paraquat are effective if prickly sida plants have emerged prior to planting.
- Apply an effective soil-applied, pre-emergence herbicide. Many soil-applied herbicides can effectively control prickly sida.
- Apply the full rate of an effective soil-applied herbicide prior to or soon after soybean planting.
- Make timely postemergence herbicide applications. Fewer herbicide options are available for postemergence control of prickly sida. The application of postemergence treatments is often based on size with smaller prickly sida plants more susceptible.
- Scout fields 10 to 14 days later for effectiveness. If prickly sida escapes initial control, a second postemergence application of herbicide can be applied. However, these are “rescue” treatments and will increase selection pressure for the evolution of herbicide resistance
- Weeds not controlled with a second application of the same active ingredient should be tested for herbicide resistance.
Photo: Rebekah D. Wallace, University of Georgia, Bugwood.org