First Clearfield varieties not `resistant' I'll continue this week discussing some of the Clearfield rice technology. In my last column I talked about the yield potential of the varieties being lower than the best conventionals. You will have all of the information up front when you make your decisions. When we first went into the Roundup Ready programs, there was little real variety information and a lot of variety misinformation. This situation will be much better.
A second factor with the first Clearfield rice varieties is the rice tolerance to the postemergence Newpath application is not as great as we would like. These first varieties are "tolerant" but they are not "resistant."
In four years of working with the technology on silt loam soils, we consistently have had some initial injury ratings that are higher than we would like. The injury is expressed primarily as stunting, sometimes with some chlorosis and even thinning of the stand. However, the rice has always recovered and produced normal yields.
We have never had rice injury with soil-applied treatments of the Newpath, but it requires both a soil-applied and followup postemergence treatment to provide the 95 percent red rice control desired.
Concerns over the injury caused the company to bring us a different rate structure in 2000. Most of our research has been with a rate of 4 ounces per acre preplant incorporated, followed by 4 ounces per acre preflood.
BASF felt that perhaps a rate of 5 ounces in the soil, followed by a postemergence rate of 3 ounces per acre might lesson the injury potential. In 2000, we saw essentially no difference in red rice control or rice injury, when we compared the 5/3 rates to the 4/4 rates.
Our Section 18 label, if granted, will have the option to use either. The 4/4 rates will be emphasized in heavy red rice infestation, which is where most of it will be used this first year. My concern with the 5/3 rates is if the soil-applied treatment fails for any reason, 3 ounces per acre is not enough to regain control postemergence.
I have used the Command analogy when discussing the Newpath injury. If you use Command, you had better be prepared for white rice. It doesn't always occur, but be prepared (have the Maalox handy).
With the Newpath/Clearfield system, be prepared for some postemergence stunting that can actually get up in the 30 to 50 percent (compared to the untreated), and that can hang around for a couple of weeks. As with Command, however, when the rice recovers, it recovers quickly and should produce yields equivalent to those produced with other herbicide standards.
In some extreme injury cases in our plots, we observed some maturity delays from a few days up to a couple of weeks in the worst case. However, these were not the norm, and the rice produced normal yields. If one even assumed the worst and some maturity delays occurred, these varieties are plenty early.
The second-generation Clearfield rice varieties should answer the injury question. It appears they will have at least 10 times the tolerance of these first two. All indications to this point are they can be called resistant, rather than just tolerant.
Hopefully these articles haven't dampened your enthusiasm for the Clearfield rice technology. Mine sure isn't. We are just better served when we go in with both eyes wide open. Everyone wants the red rice control, and this technology is capable.
There will just be some tradeoffs with this first generation technology. However, the technology will get better and better.
If you can manage the red rice outcrossing issue on your farm (which I will discuss in several future articles), we should be able to wage a better fight with this weed than we have in the past.