As many of you are aware, many of our grass species in California rice are resistant to multiple herbicides. Late watergrass aka "mimic" (Echinochloa phyllopogon), early watergrass (E. oryzoides) and barnyardgrass (E. crus-galli) are among some of our most competitive weed species, causing large yield reductions when uncontrolled.

One of the last remaining chemicals that our grass species are not yet resistant to is pendimethalin. Commercial formulations for pendimethalin registered for California rice are Prowl H2O and Harbinger.  Prowl H2O is a delayed pre-emergent herbicide applied onto dry, drill-seeded fields. Harbinger is also a delayed pre-emergent herbicide, but the Harbinger system can be used in fields that are seeded by air. Both are viable uses of the chemical, and which one you choose will depend on your available equipment. For more information on how to apply, refer to the product labels. 

Although I have used Prowl H2O in field trials and have a pretty good idea of its efficacy, I was curious to see how Harbinger looked in the field, since I have not yet had the opportunity to use it in a trial. I recently visited Rice Researchers, Inc., a rice breeding facility in Glenn County, where they are using a Harbinger-based program, for the second season. The photo (below) shows the rice at about 30 days after seeding. No weed species were present in the field. This is after one delayed pre-emergent Harbinger application.

Rice at 30 days after seeding, treated with Harbinger (pendimethalin) as a pre-emergent herbicide

It is too late to utilize pendimethalin this season, but for help incorporating pendimethalin into your herbicide plan for 2018, talk to your PCA, or give one of the UCCE Rice Advisors a call. Especially for growers that have herbicide resistant grasses, it can be a valuable tool in reducing grass populations. 

Over the past year, weedy rice has become a top issue in California rice, both for individual growers and for the industry as a whole. Working together, the University of California Cooperative Extension and the California Rice Commission have come up with a set of tools to assist in getting control of this pest. Of course, none of it would be possible without the input and cooperation of the Pest Control Advisers (PCAs) and California rice growers, who are the first line of defense in dealing with weedy rice. Additional assistance in material development and funding have come from the California Rice Research Board, the California Crop Improvement Association and the staff at the California Rice Experiment Station. 

New website on California weedy rice information: www.caweedyrice.com

A new website, www.caweedyrice.com, contains all of the most up-to-date information regarding weedy rice in California. The website covers identification, management, and weedy rice sample submission. 

Poster and pamphlet for weedy rice identificaiton in California

An identification pamphlet was mailed out by the California Rice Commission a couple of weeks ago to most growers and PCAs. If you need additional pamphlets, they are available at your local UCCE office. Identification posters will be distributed to Agriculture Commissioner's offices, PCA offices, and rice mills and distributors in each county in the next few weeks. They are also available at your local UCCE office upon request. 

Weedy Rice Reporter App for California rice: available in GooglePlay and ITunes stores

To report an infestation of weedy rice, a new app is also available for download from the Google Play and ITunes stores. 

The "Weedy Rice Reporter" app will let you send up to six pictures and aGPS location taken with your phone toUCCE RiceAdvisors so that we can confirm or rule out weedy rice. OnlyUCCE RiceAdvisors will be able to access any app submissions. We hope that the app will help us identify  infestations early so that management actions can be implemented to eliminate weedy rice from the fields. 

Mexican sprangletop that has already set seed (about 20 days after rice seeding)

I went out on a few farm calls in the past week, and have noticed a trend. Due to the unusually wet weather this spring, some of the weeds are already producing seed out in the field! This occurs when the field was moist or wet in the spring, and was not tilled or sprayed prior to planting.

If you have weeds that are already setting seed, follow the steps below:

1)      First, make sure to get proper identification of the weed species. Some weed species will produce seed and that seed can germinate and send up a second flush of weeds, in the same season! They are:

1. Smallflower umbrella sedge
2. Mexican sprangletop

NOTE: There are two types of sprangletop: Mexican and Bearded. Only the Mexican sprangletop will set seed that will germinate this season. Bearded sprangletop seed is dormant and won't germinate until the 2018 season.

Bearded sprangletop (left) and Mexican sprangletop (right). Photo: Matthew Quinton

2)      If you have one of the above-listed species that is already setting seed, it is important to make sure that your follow-up herbicide application will control this second flush of germinating seeds. Otherwise, the amount of seed produced and deposited into the seedbank will be exponentially higher than in a normal year, because there will be two generations of plants that set seed in the same season!

3)      If you have a weed species setting seed that is NOT listed above, you will likely not be able to do much this year, as the weeds are likely too large to control with herbicide and any impacts on yield have already occurred. Plan to have an aggressive program for next year (2018)!

BUTTE®, a rice herbicide, has received federal registration in the USA as well as state registration in California. It will be available to California rice growers for the upcoming 2017 season. Gowan Company, along with SDS Biotech and Nissan have collaborated to bring this product to California rice growers. 

Early BUTTE® trials at the Rice Experiment Station, 2012

BUTTE® is a granular into-the-water herbicide that combines two modes of action: an HPPD-inhibitor (benzobicyclon), and an ALS-inhibitor (halosulfuron). It is the first HPPD-inhibitor available to California rice growers. Since weeds in CA rice have widespread herbicide resistance, BUTTE® offers a new option for resistance management for affected growers, particularly those with herbicide resistant sedges. 

BUTTE® offers excellent control of many sedges, broadleaves and grasses. For a complete list of weeds controlled and suppressed, please refer to the herbicide label. BUTTE® is applied early in the season, and requires a 20-day water hold period. As always, growers and applicators should follow all label requirements, to ensure the best weed control, and to prevent the development of resistance. 

There will only be enough product available for 2017 to treat approximately 50,000 acres, so growers interested in purchasing BUTTE® this season should talk to their Pest Control Adviser and the retail location where they normally purchase rice pesticides. 

The University of California Davis Weed Science Program has been working with Gowan to research BUTTE® over the last several years. Studies on the weed control spectrum and timing began with Dr. Albert Fischer's program, and research on rates and formulations have continued under Dr. Kassim Al-Khatib. The UC Weed Program will continue to look at herbicide combinations that best compliment BUTTE® this year. The trials will be available for viewing at the 2017 Rice Field Day.