Similar to the disease survey we did last month, UC Cooperative Extension will be surveying rice weeds this fall. The survey implementation was funded by the Rice Research Board in 2019, and pending the results of the survey this year, we plan to repeat the survey every 5 years, similar to the ongoing disease survey, which is also repeated every 5 years. 

The impetus behind the weed survey is due to the increasing numbers of new weed species that have appeared in the past several years: winged primrose-willow, weedy rice, monochoria, and recently, one (possibly two) new watergrass species. We are hoping that by conducting a survey, we may find some new species before they spread, and better establish ranges for the species we know we have. 

A crew of two people will be stopping in random fields in the major rice-producing counties. We will take soil samples from the top six inches of soil in each field. The soil samples will then be processed in a greenhouse at UC Davis, where the weeds will be grown out to identify each species present in the soil. The reason we are surveying this way, instead of surveying during the rice-growing season, is due to the use of herbicides during the season, we would have difficulty seeing the presence of weed species that are well-controlled by the herbicides.

The last time we saw a severe blast epidemic was 2011. Since then, we haven't had much blast; in fact, I had not see any blast at all during several years. I don't think 2019 qualifies as a severe blast year, but there is more blast than in the previous few years. 

Blast is caused by a fungal pathogen, Pyricularia oryzae. This fungus can affect any plant part, and usually we refer to blast according to the tissue affected. Leaf blast, node blast, collar blast, and neck blast (when it affects the node right below the panicle) are all caused by the same pathogen. 

Typical and larger leaf blast lessions, collar and node lessions.

Neck blast

Blast can surive in crop residue, move with seed, and move between fields by producing airborne spores called conidia. In California, we typically see leaf blast starting at mid tillering. Blast infection at this time causes leaf lesions that in severe cases can burn plants to the water level. However, most of the time these severe symptoms are limited to small areas of the field. During heading, neck blast can cause empty heads when infections occur soon after the panicle emerges from the boot.

Left, leaf blast that has burned plants to water level in circular pattern. Right, larger area of field affected with leaf blast.

Several factors favor blast development. Moderate warm daytime temperatures, cooler nights, and long periods of leaf moisture are good for blast development. High nitrogen rates tend to aggravate blast, and typically one can see blasted circles where plants have been killed to the water level in areas of aqua overlap. Draining fields during the season increases the risk of blast infection. 

Of the rice varieties grown in California, M-205 and M-104 were considered more susceptible than M-206. Variety M-205 has been replaced by M-209, which was released in 2015. Since there hasn't been much blast pressure in the past few years, it was not known how M-209 was going to react to blast. This year seems to indicate that M-209 might be more susceptible to blast than M-206. I still have not heard much about M-105, the M-104 replacement released in 2011. Variety M-210, released in 2018, is resistant to the blast races present in California.

If leaf blast is very severe, a fungicide application may be appropriate. However, this level of disease is uncommon under our conditions. Leaf blast does indicate the need to protect the panicles during heading with a fungicide application at about 50% heading.

 

The 2019 Rice Weed Course will take place: 

Friday, September 6, 2019

from 8:00AM to 4:10PM (Registration begins at 7:30AM)

at the 

Hamilton Road Field (on West Hamilton Rd. between Hwy. 99 & Riceton Hwy.)

and Rice Experiment Station, Biggs, CA

 

This year will mark the third rice-specific weed course at the Hamilton Road Field and the Rice Experiment Station in Biggs, CA on Friday, Sept. 6, 2019. The day will begin with an interactive field tour of the research plots (Hamilton Road Field) where attendees can get up close to the weeds and rice (bring your boots!) The course will include a hands-on weed identification session on emerging and mature weeds. In the afternoon, speakers will address several pertinent topics in CA rice, including algae, weedy rice, regulatory update, best management for grasses, and how to construct a weed management program. This course is a great opportunity to interact directly with the UCCE and UC Davis Rice Weed Research Team! 

For a full agenda and registration go to: 

https://wric.ucdavis.edu/events/rice_weed_course_2019.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:  6.0 other, 0.5 laws

CA Certified Crop Adviser: 6.0 IPM

2019 Annual Rice Grower Meetings

Sponsored by UC Cooperative Extension

-------------- 5 Locations --------------

 

WHERE & WHEN

Richvale:   Thursday, Jan. 17, 8:30am, Evangelical Church, 5219 Church St., Richvale

Glenn:    Thursday, Jan. 17, 1:30pm, Glenn Pheasant Hall, 1522 Hwy 45, south of Glenn

 

Colusa: Friday, Jan. 18, 8:30am, Colusa Casino Resort, 3770 Hwy 45, Colusa

Marysville: Friday, Jan 18, 1:30pm, Yuba County Government Center, 915 8th St. Marysville

 

Woodland: Tuesday, Jan. 22, 8:30am, Cracchiolo's Market, 1320 E. Main St. Woodland

 

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

                Doors open at 1:00 pm and meetings start at 1:30 pm at Glenn and Marysville.

 

Program

8:00 a.m. (1:00 p.m.) Doors open, sign‐in, coffee

8:30 a.m. (1:30 p.m.) Call meeting to order

California Rice Commission Referendum – Tim Johnson, CRC 

8:50 a.m. (1:50 p.m.) Rice Research Board Nominations – Dana Dickey, Rice Research Board

9:00 a.m. (2:00 p.m.) Rice Pesticide and Regulatory Update – County Ag Commissioner 

9:15 a.m. (2:15 p.m.) Weedy Rice and Emerging Weed Issues – Whitney Brim‐DeForest, UCCE

9:35 a.m. (2:35 p.m.) Arthropod and Disease Update – Luis Espino, UCCE

10:05 a.m. (3:05 p.m.) Season Review and Fertility Update – Bruce Linquist, UCCE 

10:35 a.m. (3:35 p.m.) Weed Control Update – Kassim Al‐Khatib, UCCE 

11:05 a.m. (4:05 p.m.) — ADJOURN —

 

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