“White Water Fire” (Bergia capensis)

The sample was collected from a rice field and was found growing inside the field. It was not growing on banks or in ditches, it appears the preferable habitat is rice fields and marshy areas. It looks similar to; redstem (Ammania spp.) but the stem itself is much larger in diameter and less dense. Currently, there is little information globally on the plant; how invasive it is and how it impacts rice fields. The plant is native to Africa and China, and has been identified in parts of Central America.Since the initial identification, the Butte County Department of Agriculture has surveyed additional rice fields and did not find it in any other locations. One of the common ways of spread is the cultivation of rice. As of this date it has only been found in three checks of one rice site.

As with all noxious weed species, in commercial agricultural settings it is important to follow best management practices, this may include roguing field of species prior to harvest and cleaning/sanitizing of equipment post-harvest.

As more information is gained from partners at CDFA, the County Agricultural Commissioner's office will disseminate information to all interested parties.

From UCCE: Kassim Al-Khatib is currently working on developing information for herbicide control of this weed (using currently registered rice herbicides). An update will be forthcoming at the winter grower meetings. Stay tuned!

Winged Primrose Willow (Ludwigia decurrens)

Winged primrose willow (WPW) is rated a Category A pest by the California Department of Food and Agriculture (CDFA), meaning that it is subject to enforcement action if found in a field. Its presence in a seed field also disqualifies that field from seed production. It was first found in Butte County rice fields in 2011. Since then, it is not known to have spread into other counties, but it is still found along major irrigation canals and thus has the potential to move.

It starts flowering in July or August, so the big, yellow flowers should be easy to spot if you have it in your field. It tends to grow in drained areas, or along field margins (levees, irrigation ditches, etc.) The seed pods, roots, and stems can float, so until it is eradicated, there is a chance that it could end up in other areas outside of Butte County. It propagates by seed, but parts of stems or roots can re-grow into plants.

Herbicide applications are effective when the weed is small, but will not be effective as the plants grow taller (more than 1 foot tall).

Effective herbicide applications are:

1. Early water active herbicides:
   1. Bolero Ultramax
   2. Cerano
   3. Granite GR
2. Follow-up foliar 
   1. Early: Sandea, Londax
   2. Late: Grandstand or Grandstand/Propanil mix

The only means of dealing with it when it is large is by pulling it out and disposing of it. Disposal should be into a trash can, not on field edges.

Photos by Luis Espino, UCCE

To distinguish from common primrose, the WPW has 4 petals (see above photo) and the common primrose has 5 petals. Both are yellow in color. The winged primrose stem has wings on the stem (see below) in cross-section.

As always, please be on the lookout for unusual weeds, and report them to your local Farm Advisor (Michelle Leinfelder-Miles in San Joaquin, Luis Espino in Butte or Glenn, or Whitney Brim-DeForest in Sutter, Yuba, Placer or Sacramento).

This year we saw severe blast in some areas of the Valley. I did not see any leaf blast during tillering and only noticed blast during heading. After talking with some growers and PCAs, it seems that this was common in several areas. I also saw and got reports of severe blast in drill or dry seeded rice. In these cases, the blast was so severe that even fungicide applications were not able to reduce the blast incidence significatively. Kernel smut was also an issue in some fields, but it did not seem to be as bad an issue as blast was. Tiller diseases were average, but I seemed to notice more aggregate sheath spot this year than previously.

Why was blast more prevalent this year? Several factors can increase the incidence of blast, but two that come to mind are excess nitrogen and relative humidity. With many fields being fallowed last year, there might have been more nitrogen in the soil available for the plant. If the rate of aqua N was not reduced, the field may have ended up with some excess nitrogen that could have made blast a problem

          Fig. 1. Maximum and minimum percent relative humidity for 2022 and 2023 at the Williams CIMIS station.

Why do we see more severe blast when dry or drill-seeding? It is not clear why, but it may have to do with how blast is transmitted from residue or seed to seedling. There might be also some physiological changes in the plants that make them more susceptible.

The only blast resistant variety commercially available at this point is M-210. I did not see any blast or got any reports of blast in M-210. In areas where blast is a common occurrence, and when dry or drill-seeding, I would recommend using M-210. Variety trials from previous years have shown that M-210 yields the same as M-206. I will compare M-206 and M-210 yields from this year's variety trials and present them during our winter meetings.

Another common question I get is if azoxystrobin (the active ingredient in Quadris) is still effective against blast. I was able to set up a trail in a field in Glenn County and results showed that the most commonly used rate of Quadris (12.5 oz/a) was effective against blast (fig. 2). There could be some differences in susceptibility to the fungicide in different areas, so more trials are needed to answer this question thoroughly.

Richvale:      Tuesday, January 9, 8:00 am, Evangelical Church, 5219 Church St., Richvale 

Willows:       Tuesday, January 9, 1:00 pm, Glenn County Office of Education, 311 South Villa Avenue, Willows 

Colusa:        Wednesday, January 10, 8:00 am, CIP Conference Room, 100 Sunrise Blvd., Colusa

Yuba City:    Wednesday, January 10, 1:00 pm, Veterans Hall, 1425 Veterans Memorial Circle, Yuba City  

Woodland:    Thursday, January 11, 8:00 am, Norton Hall, 70 Cottonwood St, Woodland 

TIME: Doors open at 8:00 am and meetings start at 8:30 am at Woodland, Richvale, and Colusa.

          Doors open at 1:00 pm and meetings start at 1:30 p, at Glenn and Yuba City. 

Program 

8:00am       (1:00pm)       Doors open, sign-in, coffee

8:30am       (1:30pm)       Call meeting to order 

8:35am       (1:35pm)       Rice Research Board Nominations - Lacey Stogsdill, Rice Research Board 

8:45am       (1:45pm)       County Agricultural Commissioner Updates

9:00am       (2:00pm)       Fertility Update, Bruce Linquist, UC Davis

9:20am       (2:20pm)       Rice Experiment Station Update, Dustin Harrell, Rice Experiment Station Director 

9:40am       (2:40pm)       Weed Management Update, Kassim Al-Khatib, UC Davis 

10:00am     (3:00pm)       BREAK

10:15am     (3:15pm)       Yield Contest - Bruce Linquist, UC Davis 

10:30am     (3:30pm)       Invertebrate Management Update - Ian Grettenberger, UC Davis 

10:50am     (3:50pm)       Disease Management Update, Luis Espino, UCCE 

11:10am     (4:10pm)       Emerging Weeds - Whitney Brim-DeForest, UCCE 

11:30am     (4:30pm)       ADJOURN 

***Applied for DPR and CCA CE credits***