Every year, the University of California Cooperative Extension, in cooperation with the Rice Experiment Station (RES), conducts rice variety trials in several locations of the Sacramento Valley (fig. 1). The trials are conducted at the RES and eight farm locations across the Sacramento Valley, and one location in the San Joaquin Delta (not on the map) representing the main production areas of California. In 2023, the South Yolo trial was not conducted. Plots in the Sacramento Valley trials were 200 ft² and hand seeded while in the San Joaquin Delta trial plots were 150 ft² and drill seeded; seeding rate for all trials was of 150 lbs/a. Grower cooperators treated the trial in the same manner as the rest of the field. Parameters evaluated in the trials included seedling vigor, days to 50% heading, plant height, lodging at harvest, grain moisture at harvest, and grain yield at 14% moisture. Varieties are replicated four times. In this summary, only yields are presented. All other parameters are included in the complete report, which will be available on our website at the end of February (http://rice.ucanr.edu).

In California, most acreage is devoted to high quality medium grain varieties. In 2023, over 94% of the acreage was grown to medium grains. There are currently six medium grain varieties to choose from: very early (M-105), early (M206, M-209, M-210, and M-211), and late-maturing (M-401 – a premium medium grain). Here are some things to consider when making a choice.

M-105 is the earliest variety; although it is only 1-2 days earlier than M-206 in the northern part of the valley but it is 3-5 days earlier in the southern cooler parts of the valley. It also has excellent yield potential. Last year it had the highest yields in our yield contest with a yield of 132.5 cwt/ac. It also tends to yield the highest in our variety trials located in the southern portion of the valley (south of hwy 20). It is an excellent choice to plant at the start of the season in order to get an early start on harvest. The knock on M-105 is that it can lodge; however, in our variety trials (and other trials at the Rice Experiment Station), there is no indication that its lodging potential is different than M-206.

M-206 and M-210 are nearly identical except that M-210 has blast resistance. They are both early varieties and stable across environments. In areas with blast, or if dry seeding, M-210 is an excellent choice. In 2023, blast was wider spread than normal. For growers that have only used M-206, try using M-210 on a field and see how it compares. You should have very similar results.

In terms of yield potential, M-209 and M-211 have the highest yield potential. M-211 regularly out yields other medium grains by 1-3 cwt/ac in our variety trials in the northern part of the valley (north of hwy 20). Both M-209 and M-211 are longer in duration than M-206 and neither are well suited to cooler areas (M-209 being the least suited). Duration is also important when thinking about water limitations as they require more water to irrigate. Achieving good milling quality is one issue with these varieties. Milling quality drops rapidly when harvest grain moisture drops below 20%. Given this, it may not be wise to plant these varieties on a large number of acres where a timely harvest may be difficult. On a positive note, these varieties are less prone to lodging. This is partly due to thicker tillers. Some growers indicate that managing the rice straw in M-211 is harder than for other varieties. Finally, where kernel smut is an issue, M-209 is one of the more susceptible medium grains.

Finally, California's first herbicide resistant variety M-521 has been approved for release. However, seed production for this variety will not proceed until the herbicide is approved.

Background

White water fire (Bergia capensis) was found in September of 2023, by the Butte County Agricultural Commissioner's office in a rice field in Butte County. The weed was identified by the California Department of Food and Agriculture. It is the first find of this weed in California, and possibly in the United States. It is native to Africa, southern China, and tropical Asia, and it is known to be in rice fields in Europe, Central and South America, as well as the Caribbean. It was likely transported in seed to rice-growing areas and has been established in those locations for many years.

In Butte County, the weed was only found in one rice field, and the Agricultural Commissioner's office surveyed surrounding rice fields but found no additional infestations. The method of introduction in California is unknown at this point. 

It currently has a “Q” rating by CDFA: “An organism or disorder suspected to be of economic or environmental detriment, but whose status is uncertain because of incomplete identification or inadequate information”. At this point, it is not considered a quarantinable pest so if it is found, there is no penalty or restriction for finding it in a field. 

Identification

White water fire looks similar to another common rice field weed, redstem (Ammania spp). However, the two species are not from the same plant family and are therefore not closely related. Due to the similarity, white water fire is quite difficult to identify in the field. One of the key distinctions is the thickness of the leaves, which are much broader in white water fire than in redstem. Another key distinction is flower color. The flower color of white water fire is white, whereas redstem can have either purple or red flowers. 

California rice growers will have a new herbicide available this year: Cliffhanger™, manufactured by Gowan Co. The active ingredient is benzobicyclon, which is the same as one of the two active ingredients in the currently registered herbicide, Butte®. Cliffhanger™ is a soluble liquid formulation (SC) which can be applied by ground-rig or airplane, including as a direct-stream application into the water. In contrast, Butte® is a granular formulation, as a pre-formulated mixture of benzobicyclon and halosulfuron. To use either product, applicators must attend a training and be certified.

Dates for the training are posted on the California Rice Commission calendar https://calricenews.org/events/, as well as the UC Rice website.

Controlled weeds are sprangletop, ricefield bulrush, and smallflower umbrella sedge. The application timing begins from day of seeding up to 82 days before harvest. Recommended timing for sedges is pre-emergent up to the 5-leaf stage, and for sprangletop, pre-emergent up to the 2.5 leaf stage as well as at tillering. 

Flood water should be a minimum of 4 inches when the product is applied. The active ingredient, benzobicyclon, is a proherbicide, meaning that it is not active until it comes into contact with water. Therefore, for maximum efficacy, water should be held in the field for at least 5 days. Longer periods of flooding will result in better efficacy, whereas a drain soon after application will both reduce efficacy as well as encourage a new flush of weeds. The recommended waterhold is 10-14 days for maximum efficacy. 

Cliffhanger™ should only be applied once per season. It is not recommended that it be applied in the same season as any other HPPD-inhibitor product (Butte®). Applying both in the same season can select for herbicide resistance and may cause significant phytotoxicity to the rice. Repeated applications, both during the same season, or season after season, can select for resistance, particularly in sprangletop, ricefield bulrush, and smallflower umbrella sedge.

Remember to always follow all label instructions when applying any pesticide, as the label is the law. Make sure to pay particular attention to the Use Precautions and Restrictions. Consult your local Agricultural Commissioner's Office regarding buffer zones and aerial restrictions, before making any applications. Label and SDS: https://www.gowanco.com/products/cliffhanger-sc-herbicide