- Author: Ian Grettenberger
- Author: Luis Espino
Want to help make sure your freshly planted rice fields don't look like the muddied mess on the left below (vs. clear on right) following a pyrethroid application? Wondering if your tadpole shrimp are becoming less susceptible to pyrethroids? We do too! Pyrethroids are widely used for managing resistance and resistance seems to be a growing issue.
We are looking for additional fields where we can sample tadpole shrimp to test for pyrethroid resistance. We will be gathering soil/shrimp and then using these samples to run laboratory bioassays and measure susceptibility. The goal is to start measuring precisely how susceptible populations are in different fields. This will help us determine precisely how resistant known resistant populations are, how prevalent low levels of resistance are, and how “susceptible” currently susceptible populations are to generate baseline data. This will help generate the long-term baseline data we need to stay on top of this issue. We will anonymize any publicly available data. In addition, we hope that by measuring resistance in individual fields, we can help you by noting any susceptibility slippage that may not have shown up yet in terms of control. We can also help address questions about whether lack of control is due to resistance or application issues.
Types of fields:
- Fields with known resistance to pyrethroids in tadpole shrimp (control issues).
- Suspect fields where you think resistance is an issue, but it is a just a hunch or a concern.
- Any other field. Even if pyrethroids have been working well, it is still good to know susceptibility levels and for us to generate baseline data.
What we need:
- Access to field(s)
- Summary of your ability to manage tadpole shrimp with pyrethroids, any declines in susceptibility, etc.
If you are interested please email or call (Ian) at imgrettenberger@ucdavis.edu or 530-752-0473.
- Author: Luis Espino
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.
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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.
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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.
- Author: Whitney Brim-DeForest
Weedy Rice Workshop
10:00 – 12:00 followed by lunch
August 1st, 2019
Colusa Casino Chairman's Room
Agenda
- 9:30 Doors Open, Sign In
- 10:00 – 12:00 Presentations
- Introduction and Update on Weedy Rice Distribution
- Regulatory Update
- Rice Seed Quality Assurance Program Update
- Weedy Rice Biology, Ecology, Genetics, and Identification
- Effect of Weedy Rice on Plant Growth and Yield
- 12:00 Lunch
There is no registration cost, but registration is required.
Register online at the UC Rice On-line website (rice.ucanr.edu)
Note: Enrollment is limited to 50 participants, so please enroll early. Seats will be filled on a first-come basis.
