California alfalfa growers will want to act soon to control outbreaks of dodder, a troublesome parasitic weed, says Steve Orloff, farm advisor with University of California (UC) Extension.

Initial emergence can be as early as early March in the state’s San Joaquin Valley, although dodder is typically not observed in many parts of California until early summer. Treat fields now with pre-emergence dinitroaniline herbicides like Treflan or Prowl, recommends Orloff in a recent post on the UC Forage & News Blog. To be effective, the herbicides must be incorporated with irrigation or rain (ideally ½” of rain) before dodder emerges.

“The key to effective dodder control is not to allow any seed production,” Orloff says. Dodder plants that escape a pre-emergence treatment should be controlled before they flower (beginning in June through August) and set seed by spot-treating with Pursuit or by flaming.

In Roundup Ready alfalfa, Roundup can effectively control dodder, Orloff says. “Depending on the infestation level and the timing of treatment, a sequential application of Roundup might be needed rather than a single application for complete control. However, using this tool, nearly 100% dodder control is feasible.”