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.

Webinar - U.S. Rice: The Sustainability Powerhouse

An American Society of Agronomy webinar sponsored by The Rice Foundation and USDA Natural Resources Conservation Service.

Date:  Wednesday, October 16, 2019

Time: 12:00 Noon Eastern/11:00 AM Central/9:00 AM Pacific

Description: The U.S. rice industry's commitment to sustainability dates back generations, long before the word “sustainability” became a popular, if difficult to define, term. In this webinar, you'll hear from U.S. rice farmers on why preserving resources and providing habitat is important to them, and why end users are making investments around the implementation of more sustainable practices.

 

Speakers:

Jennifer James, Farmer and Chairwoman USA Rice Sustainability Committee

Bill Jones, Rice Agronomy Manager, Anheuser-Busch

Paul Buttner, Manager of Environmental Affairs, California Rice Commission

George Dunklin, Owner, Manager Five Oaks Lodge and Past President Ducks Unlimited

 

Access information

Register for the webinar here: https://www.agronomy.org/education/classroom/classes/738

 

You do not have to be a certified crop advisor or professional agronomist to sign up for the webinar. If you do not already have an account with the agronomy societies you will have to create an account here. Once you create an account and are registered, you should receive an email from GoToWebinar with a link to access the webinar. If you have trouble creating an account or registering for the webinar, please contact Lydia Holmes

 

CEUs:

CCA/CPAg: 1.0 Sustainability

CPSS/CPSC/CST: 1.0 Professional Meetings

 

 

UC Cooperative Extension is conducting a survey of rice diseases this fall. The objective of the survey is to document the incidence of rice diseases in Sacramento Valley rice fields so that the Air Resources Board agrees to continue to allow the rice industry to burn up to 25% of the acreage. Every five years, the Board has to re-approve the straw burning program. One of the reasons for letting growers still burn is disease control. Therefore, it is important to show that diseases are still present in rice fields.

A crew of four to five will be stopping in random fields in the major rice producing counties and inspecting for the presence of diseases in 30 sites in each field. We will look for stem rot, aggregate sheath spot, kernel smut, and blast. The precise location of each field won't be disclosed, only the general location and County. So far, we have inspected 10 fields in Butte County, and have found very low levels of blast and kernel smut. Stem rot and aggregate sheath spot are more variable; we have found fields with very little of these diseases and fields with a lot. 

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.