Shepherd's purse (Capsella bursa) is one of the most widespread and difficult to control weeds here during this time of year. It is especially difficult to control when preemergence herbicides and sprinkler irrigation are used. The seed for shepardspurse is extremely small. It is less than 1mm or 1/25th inch in diameter. It characteristically germinates right on the soil surface and unless the herbicide is concentrated there, they will not be controlled. The seedlings for this weed are generally not visible until the plant has 4 or 5 leaves. It is considered one of the most prolific weeds and although it is an annual, it can produce multiple generations in one season. When preemergence herbicides fail, it is likely because the herbicide is located below the germinating seed. It is sensitive to many postemergence herbicides, but the small seed and low growing foliage make it difficult to contact. The seed readily moves with water and wind.

To contact Barry Tickes go to: btickes@ag.arizona.edu.

For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.