I've been getting calls about sedge surviving propanil applications. Last year, research conducted by Albert Fischer showed that there are populations of smallflower umbrellasedge that are truly resistant to propanil (read the article here). However, just because sedge was not controlled by propanil, it doesn't mean it is resistant. Some other explanations for lack of control are:

• Propanil was applied too late. The older the weeds, the harder they are to kill.
• The rice canopy was large and shielded the weed during the application.
• Water level was too high and weeds were not exposed.
• Incompatibilities in the tank mix.
• Dosification errors.
• Equipment failure.

If you suspect you have propanil-resistant sedge in your field, the UC Rice Weed Project can test seed from the suspected weeds and confirm or rule out resistance. Collect a seed sample, fill out the Resistant Weed Seed Testing form (download it here), and send or drop off the sample at the Rice Experiment Station in Biggs. The testing is conducted early in the spring and the results made available to you ahead of seeding.