Albert Fischer, professor, and James Eckert, staff research associate, both in the Department of Plant Sciences at UC Davis, collected smallflower umbrella sedge seeds from eight fields where resistance was suspected. They grew the weeds in pots, then sprayed them with propinal at half the field rate, the recommended rate and twice the field rate. The herbicide did not control the weed seeds collected at four of the fields. The seeds from the other four fields were well controlled by propinal.
Luis Espino, UC Cooperative Extension advisor, rice, said the field failures with non-resistant sedge could have resulted from mistakes in herbicide application. The propinal-resistant seed were also found to be resistant to several other herbicides.
To prevent weed resistance, Espino said, it is best to alternate modes of action whenever possible.