I have been a weed scientist for a long time and have worked with different cropping systems. The rice cropping system is very interesting to me because of its uniqueness and global impact as one of the world’s major food crops. All of its components, including a good weed control program, have to be managed appropriately to achieve the intended results.
Grasses, sedges and broadleaf weeds make up the spectrum that challenges California rice production. I would put grasses and sedges as No. 1 because they are equally important. Broadleaf weeds would be No. 2. But to have a sustainable rice production system, we have to manage them all. It’s important to identify the weeds present in each field, and then tailor your herbicide program accordingly. Different herbicides have activity on different weeds.
A Balancing Act: Weeds And Restrictions
Because weed resistance is becoming more of a problem in California rice fields, farmers need to have a resistance management program in place. Although weed control programs rely heavily on herbicides, we are trying to diversify by using an integrated pest management approach that incorporates other practices as well. For example, our growers plant clean, certified seed and level the ground so they can put water on quickly to help suppress weeds. Land leveling also allows them to take water off, make pinpoint herbicide treatments and then efficiently return water to the field. Water is a nice tool to manage weeds in rice. Fields also are monitored and scouted regularly.
We try to rotate herbicide modes of action to delay resistance and offer a free weed-testing service farmers to determine if the weed is resistant to the herbicide they are using. We test them against other herbicides as well.
For example, Granite — an ALS herbicide — is a big component of our weed control program because of its broad-spectrum weed control. In these tests, we have found ALS-resistant weeds, but not all of them are resistant to Granite. If farmers have ALS-resistant weeds, they can switch to another herbicide with a different mode of action or they can continue to use Granite because not all ALS-resistant weeds are cross resistant to Granite.
Today we are conducting research to develop a systems approach to weed control. By including herbicides as part of the system but not the only means to manage weeds, we potentially can decrease the impact of herbicide-resistant weeds in the future. Our goal is to improve the efficacy and optimize the weed control program we have now.
California rice farmers continue to produce the highest yield in the country. They follow new developments in weed control closely as this is the No. 1 challenge for our producers.
Dr. Kassim Al-Khatib
Weed science professor and Cooperative Extension Specialist
Department of Plant Sciences – UC Davis
- Ph.D., crop physiology, Kansas State University
- Melvin D. Androus Endowed Professor for Weed Science 2015-present
Former director of the statewide UC Integrated Pest
- Research interests include integrated pest management, weed control, pesticide drift, herbicide resistant plants and sustainability among others
- A member of several professional societies, including the International Weed Science Society and the Weed Science Society of America
- Recipient of numerous honors and awards
- Enjoys traveling, playing tennis and following sports such as football and soccer