Managing herbicide resistance in rice
California’s rice industry produces nearly 2 million tons of rice annually, making it the second largest rice growing state in the nation and contributing nearly $500 million dollars to the state's economy. For the rural Sacramento Valley communities of Colusa, Butte, Sutter, and Yuba counties, rice is the predominant crop. California's rice is exported to Asia, the Middle East and Mediterranean markets, and is distributed throughout the United States.
In short, rice is an important industry in California. But it would have a hard time surviving without the help of the UC weed scientists who work to control the plethora of weeds that thrive in a rice field’s wet, clay conditions.
Much of California’s rice is grown continuously in the same fields and growers are heavily dependent on herbicides for effective weed control. The trouble is, some herbicides like the workhorse molinate are no longer available and – even more challenging - the multitudes of broadleaves, grasses, sedges and other weeds that grow along with rice are developing resistance to herbicides at alarming speed.
“As California rice growers find their herbicide options dwindling because of widespread herbicide resistance in the major weeds of rice, the need for non-chemical means of manipulating weed management practices is imperative,” says Weed Ecophysiologist Albert Fischer who heads the department’s work with herbicide-resistance in rice along with Cooperative Extension Specialist Jim Hill. “Herbicide reductions and related weed resistance is a very serious problem.”
Fischer and his team have been experimenting with alternative stand establishment techniques to minimize weed populations and results of their four-year study are very encouraging. In brief, they show that alternating weed establishment environments – such as alternating from aerobic to anaerobic rice stand establishments with a stale seed bed – can successfully reduce weed infestations without affecting yield.
“Alternating weed establishment environments creates a shift in weed species and can reduce herbicide-resistance pressure,” Fischer says. “This strongly demonstrates the potential for controlling resistant weeds and lowering herbicide use.”
For a more complete look at the four-year trials, click here.
