I have been alerted of three instances where pyrethroid applications for TPS control have failed. One field had been treated with a pyrethroid two times, and TPS were still alive in great numbers. I collected some of these surviving TPS and run a quick test to see if they would survive exposure to lamba-cyhalothrin or copper.
|Treatment rate||% survival after 24 h exposure|
|Lambda-cyhalothrin 1 mg/lt||70|
|Lambda-cyhalothrin 2 mg/lt||0|
|Copper sulfate 4.5 mg/lt||0|
The lamda-cyhalothrin 1 mg/lt concentration is roughly equivalent to 5 times the field rate applied to a 4 inch flood. It is remarkable that TPS were able to survive this concentration. The copper concentration is equivalent to a 5 lbs/a rate. In another test, I had TPS survive the equivalent of half and double the rate of a lambda-cyhalothrin application. I'm currently testing the TPS collected from a third field.
Make sure your TPS treatments are being effective. If TPS are surviving a pyrethroid treatment, use copper sulfate to kill survivors. We need more testing to figure out what is going on, but it is a good idea to prevent surviving TPS to lay eggs that may create more problems next year.
If you notice TPS surviving a pyrethroid treatment, contact me. At this point the issue seems to be in only a few fields, but it is important to learn of any other instances of control failure.
I have been getting some questions about the new variety M-209. The most common question is how it responds to blast. Unfortunately, we do not know the answer to that. The last two years there has been very little blast in the valley, so we haven't been able to evaluate M-209's response to blast. However, we know that one of the "parents" of this variety is M-205, which is very susceptible to blast. To those growing M-209, I would recommend avoiding lengthy drains and to be conservative in their N fertilization. If blast starts showing up in the valley, a preventive fungicide treatment may be appropriate.
Another question regarding M-209 is how its quality is affected by harvest moisture. In a range of harvest moistures, M-209 has better head rice yield than M-202, but it is slightly below M-206. M-209 is best harvested above 18% grain moisture content.
For more information, see the M-209 Agronomy Fact Sheet.
This is a question I have gotten recently. Should a N topdress be planned or can it be avoided? Research conducted by Bruce Linquist, UCCE Rice Specialist, has shown that a N topdress is unnecessary if an adequate amount of N is applied at planting. Here's part of an article he wrote earlier this year for Rice Farming Magazine:
Top-dressing N is expensive as it requires an airplane, and the fertilizer is expensive relative to aqua-ammonia. Top-dress N applications are absolutely needed if the plant is N stressed, which typically shows up as yellowing of lower leaves.
That said, I suggest planning so a top-dress N application is unnecessary. Research conducted on-station and on-farm has shown that if an adequate amount of N is applied at planting, a top-dress is not needed to achieve maximum yields.
If you find yourself constantly needing a top-dress N application at PI, you might want to increase your preplant N rate. I don't want you to necessarily take my word on this, but I encourage you to do your own testing to see if this is really necessary. A simple test involves three treatments across a field: (1) standard preplant N rate with no top-dress; (2) standard preplant N rate with top-dress and (3) increased preplant N rate with no top-dress.
The total amount of N in treatments 2 and 3 should be the same, and this will tell you if yield improved with a split. Having treatment 1 in the field lets you know if a top-dress or increased N rate was necessary to begin with. At harvest, use a combine with a yield monitor to test for differences within the treatments.
In addition to the well-known rice weeds we deal with every year, there are a couple of weeds I want to bring to your attention this year. One is an invasive and the other has been with us for a while.
The winged primrose willow was identified in 2011 in several rice fields near Richvale in Butte County. Since then it has spread to several other fields, up to 3.5 miles south of Richvale. Winged primrose willow was recently given an “A” pest rating by CDFA. What this means is that this weed is now considered to be of economic importance and may trigger an enforcement action by the state. Currently, no actions are being considered, but its presence will disqualify a seed field. The rice industry is implementing an outreach, monitoring and control program for winged primrose willow to stop its spread and reduce infestations.
Red rice has been found in a few locations in California over the years. In 2003, its presence was confirmed in six fields. In some of these fields, growers were able to eradicate it. However, since then, red rice has been found in other locations. The exact number of locations currently affected is unknown, but estimates are around 15. At this moment, red rice does not represent a threat to the industry. But if this weed spreads, it can severely impact the rice industry, affecting yields, quality and production costs. To get an idea of its potential impact, just ask any southern rice grower about red rice and you'll get an earful.
UCCE will be collaborating with other organizations and agencies to get information on identification and management of these weeds. We will be sending information out through our newsletters and websites, so make sure to be subscribed. In the meantime, here's a list of links with relevant information on these two weeds.
Winged primrose willow:
UC IPM Website (under Emerging Pests in California)
June 2012 Rice Briefs newsletter: Behavior of winged primrose willow and herbicide options for control
Last month I contributed a small article for Rice Farming Magazine. I used data generated by the UC Weed Project to illustrate the point of how difficult, complicated and expensive weed control can be once herbicide-resistant weeds are established in a field. Well, a very observant PCA noticed that there was a mistake in my example. Here it is: "However, if dealing with ALS-resistant watergrass and propanil-resistant sedges, this program would be a failure. In this case, a more appropriate program may consist of application of a tankmix of Granite GR and Shark at the 2.5 leaf stage of rice, followed by application of a tankmix of Abolish and Regiment at the 5 leaf stage of rice." Obviously, you can't tankmix Granite GR and Shark! What I meant to say was, a same day application of Granite GR and Shark at the 2.5 leaf stage. This base application gave very good control of umbrellasedge and broadleaves, good control of bulrush, but mediocre control of late watergrass. The follow up application of Abolish and Regiment resulted in excellent control of all weeds.
Apologies for the confusion!