Rice sticks out like a sore thumb in terms of herbicide drift.
It is the only crop that will not tolerate even small amounts of glyphosate, in a sea of Roundup Ready corn, soybean, cotton and burn-down fields scattered across the Delta. That thumb has even become more sensitive this year with the increase in Clearfield rice acres.
Clearfield rice, of course, refers to rice that has been bred to tolerate the herbicide Newpath (imazethapyr). Conventional rice will not tolerate Newpath. Newpath was selected for this reason so that it would control red rice in-season.
The technology has been extremely effective for the past eight years, with only a small amount of resistance showing up at this time. Since the trait became available in higher-yielding hybrid varieties and better public varieties, its popularity has grown almost steadily every year.
The increase in acres means that more applications of Newpath are being made in and around sensitive rice fields. From the road or from the air these fields look the same. It is easy to forget that not all rice will tolerate the same herbicides now.
Many growers across Arkansas made a good faith effort this year to try and keep Clearfield fields together, to make it easier to spray them. However, often what happens is one guy did not get the word, planted conventional rice and ended up surrounded by Clearfield on all sides. This makes it almost impossible to spray around.
There is a project under way in Clay County, Ark., to try to mark these fields with a uniform color coding system, a series of flags or markers that indicate what type of crop is in a field. Some of us are watching this program and may propose a statewide coloring system for fields in the near future.
In the meantime, what do you look for if you think your field has been hit by Newpath drift? First it looks a lot like Roundup drift on rice. The problem with telling them apart is that little sick rice, looks like little sick rice. There are not a lot of distinguishing characteristics. Rice will be stunted and stay stunted, have pale yellow leaves and dead tillers.
If you think you have Newpath drift, look for patterns of drift in the field, does the injury get worse from one side to the other? What about the levees? They are often the best diagnostic tool. Is one side dead and the other alive or less injured? If so, the drift came from the direction of the dead side. Is there any Clearfield rice present in the field or surrounding fields?
I have been in two fields of 723 this year that had a few scattered plants in them that apparently were Clearfield rice. They were in the row and occurred about every 20 feet or so. These plants were about 4 inches taller than the injured rice and showed no signs of Newpath injury. This is a good indicator that the field was hit by Newpath and not Roundup.
After this year I am convinced Newpath drift is worse than glyphosate. One factor that makes this worse is the inclusion of higher rates of Newpath on the expanded label a while back. Drift from a 6-ounce rate is worse than from a 4-ounce rate.
I have been forced to re-think my drift recommendations where the higher rate was used. What I used to assume would grow out of it in 10 to 14 days, now may take two weeks longer or not grow out at all.
In our research, the 4-ounce followed by 4-ounce rate of Newpath always looked as good as the higher rates in sequential programs in terms of grass and red rice control. Where grass got big, it was better to add Facet, RiceStar HT, or another grass product to the mix than it was to add more Newpath. I usually only recommend a higher rate in one application when the field may only get one shot for whatever reason.
Management of Newpath drift fields takes patience. Often the recommendation is to do nothing and wait on the rice to recover. I rarely recommend that a field be plowed up and started over. With the higher rate of Newpath, I have looked at two fields this year that may end up in soybeans.
Do not flush the field unless you have to. Newpath is active in the soil. Do not try to flood too soon. You need to see 2 to 3 inches of new healthy green growth. Our research has shown that the old recommendation of flushing in fertilizer makes the field look better, but does not speed up recovery or increase yields.
For moderate drift, the highest expense may come from delaying the flood and added herbicide cost to keep an unflooded field clean for another two weeks.
A few years ago the whole Mid-South started growing Roundup Ready corn in defense against herbicide drift. Whether Newpath is needed or not, many growers are talking about planting Clearfield rice in self defense next year.
e-mail: [email protected]