- Author: Whitney Brim-DeForest
The 1st Annual Rice Weed Course will take place:
Friday, September 16, 2016
from 8:30AM to 4:15PM (Registration begins at 8:00AM)
at the
Hamilton Road Field (on West Hamilton Rd. between Hwy. 99 & Riceton Hwy.)
and Rice Experiment Station, Biggs, CA
The day will begin with an interactive tour of the Weed Science research plots at Hamilton Road. Participants will also spend time learning about weed identification for important rice weeds both at emergence and at heading. Presentations will cover emerging pests of rice, such as weedy red rice and winged-leaf primrose willow. Attendees will hear about new pesticide registrations and updates to current pesticides, as well as information regarding the new Butte herbicide. This course is also a great opportunity to interact directly with the UCCE and UC Davis Rice Weed Research Team!
For a full agenda and registration go to:
http://wric.ucdavis.edu/events/rice_weed_course_2016.html
For questions, please contact Whitney Brim-DeForest at 530-822-7515, or by email at wbrimdeforest@ucanr.edu
Credits for PCA, QAC, QAL, Private Applicator, and CA Certified Crop Adviser are pending.
- Author: Luis Espino
I have received an update from the Butte County Ag Commissioner's office regarding winged primrose willow. Germinating seedlings have been detected recently. At this point, the seedlings are very small and would be very difficult to notice. Scouts were able to find them in places where the weed had been seen in the past. But this is a good indication that conditions are now good for germination. Growers and PCAs in risk areas should be on the alert. Larger seedlings will probably be visible in 30 days.
For more information and pictures, visit the UC Rice On-line winged primrose willow page.
Photo by Evan Padgett, Butte County Agricultural Commissioner Department
- Author: Luis Espino
In addition to the well-known rice weeds we deal with every year, there are a couple of weeds I want to bring to your attention this year. One is an invasive and the other has been with us for a while.
The winged primrose willow was identified in 2011 in several rice fields near Richvale in Butte County. Since then it has spread to several other fields, up to 3.5 miles south of Richvale. Winged primrose willow was recently given an “A” pest rating by CDFA. What this means is that this weed is now considered to be of economic importance and may trigger an enforcement action by the state. Currently, no actions are being considered, but its presence will disqualify a seed field. The rice industry is implementing an outreach, monitoring and control program for winged primrose willow to stop its spread and reduce infestations.
Red rice has been found in a few locations in California over the years. In 2003, its presence was confirmed in six fields. In some of these fields, growers were able to eradicate it. However, since then, red rice has been found in other locations. The exact number of locations currently affected is unknown, but estimates are around 15. At this moment, red rice does not represent a threat to the industry. But if this weed spreads, it can severely impact the rice industry, affecting yields, quality and production costs. To get an idea of its potential impact, just ask any southern rice grower about red rice and you'll get an earful.
UCCE will be collaborating with other organizations and agencies to get information on identification and management of these weeds. We will be sending information out through our newsletters and websites, so make sure to be subscribed. In the meantime, here's a list of links with relevant information on these two weeds.
Winged primrose willow:
UC IPM Website (under Emerging Pests in California)
2013 Rice Grower Meeting presentation: Winged Willow Primrose
UC Rice Blog posts: New weed identified in California rice, and Behavior of winged primrose willow and herbicide options for control
June 2012 Rice Briefs newsletter: Behavior of winged primrose willow and herbicide options for control
Red rice:
- Author: Luis Espino
Last month I contributed a small article for Rice Farming Magazine. I used data generated by the UC Weed Project to illustrate the point of how difficult, complicated and expensive weed control can be once herbicide-resistant weeds are established in a field. Well, a very observant PCA noticed that there was a mistake in my example. Here it is: "However, if dealing with ALS-resistant watergrass and propanil-resistant sedges, this program would be a failure. In this case, a more appropriate program may consist of application of a tankmix of Granite GR and Shark at the 2.5 leaf stage of rice, followed by application of a tankmix of Abolish and Regiment at the 5 leaf stage of rice." Obviously, you can't tankmix Granite GR and Shark! What I meant to say was, a same day application of Granite GR and Shark at the 2.5 leaf stage. This base application gave very good control of umbrellasedge and broadleaves, good control of bulrush, but mediocre control of late watergrass. The follow up application of Abolish and Regiment resulted in excellent control of all weeds.
Apologies for the confusion!
- Author: Luis Espino
- Author: Whitney Brim-DeForest
The Weed program at the Rice Experiment Station (RES) in Biggs conducts herbicide resistance testing for the major rice herbicides used in California. This information helps growers improve their weed control programs if resistance is confirmed, and also helps the rice industry as a whole to keep track of resistance issues.
Sprangletop and smallflower umbrella sedge seeds are the first weed seeds to mature. If you suspect herbicide resistance, bring seeds of these weeds to the RES to be tested, together with the Resistant Weed Testing form available here. Follow the guidelines below to ensure that enough seed of the right species is collected. Later in the year we'll update these guidelines to include ricefield bulrush and watergrass.
General guidelines to collect suspected herbicide resistant weed seeds:
- Don't wait until harvest to collect seed. By then, most weeds have shattered their seeds. If you collect after harvest, you'll probably be collecting seeds from weeds growing around the field that may not be the correct species.
- Collect seed when they are mature and dislodge easily from the seedhead. In general, sprangletop matures the earliest, between rice PI and heading. Early watergrass, barnyardgrass, smallflower umbrella sedge, and ricefield bulrush follow, between rice heading and maturity. Late watergrass is the last weed to mature.
- Collect seed from areas of the field where you are certain the herbicide application in question was appropriate. Avoid field borders, tractor tire tracks, skips or areas where you suspect the herbicide was not sprayed correctly.
- Collect seed from several areas of the field. Usually, when herbicide resistance is the problem, weed growth will be distributed uniformly across the field and not just in one “hot spot”.
- Collect seeds, not seedheads. Take the seedhead and gently shake it inside a paper bag. Seeds that shatter are mature and will readily germinate. If seedheads are collected, seeds might not be mature or might have shattered already.
Collect seeds by shaking the seedheads gently into a paper bag
- Collect enough seed. In order to have conclusive results, several replications of the herbicide resistance testing are needed. When not enough seed is provided, replications may not be possible. For small sized seed weed species such as sprangletop, smallflower or sedge, collect seeds from at least 20 mature seedheads. For barnyardgrass, early and late watergrass, collect from at least 30 mature seedheads.
- Monitor seed development. If seeds are not dislodging during collection, they are probably still immature. Return in 2 or 3 days and try again.
Species specific guidelines:
- Sprangletop seeds shatter easily. Mature seedheads that have shattered their seeds will look dry, while seedheads with immature seeds will look green. Seedheads with mature seeds will have a thicker appearance than empty seedheads.
Sprangletop panicle with mature seeds
- There are two sedge species similar to smallflower. Whitemargined flatsedge (Cyperus flavicomus) and ricefield flatsedge (Cyperus iria) grow in field borders and shallow areas in the field. Be careful not to confuse them with smallflower.