Dr. Jarrod Hardke, Dr. Gus Lorenz, & Dr. Bob Scott
May 20, 2016 No. 2016-10 www.uaex.edu/rice
Yes, I do think the cold weather is the culprit behind a lot of our problems in the last week or so. Rice a little pale and not growing off as you’d expect? Rice a little banged up from herbicide and not growing out of it? Cold weather is a prime culprit. Herbicide drift hasn’t helped anything either.
We’re actually close to the 30-year average on DD50 units in the southern part of the state. However, we’ve been consistently a little low for the past couple weeks, where in other years we’ve had highly daily accumulations with an occasional cool day to bring the average down.
In the north, our accumulations have been consistently below average for the past week, getting around half the DD50 units we should normally average over that time. The devil is in the details.
While we’re accumulating heat units slower than normal in parts of the state – we’re still accumulating them. I understand if you’re rice is stacking leaves and not very tall, but understand that it’s still aging. We manage the crop best by growth stage dictated by DD50 heat unit accumulation, not by height alone.
Height does have to still be considered of course, we don’t want the initial flood to cover the rice and force it to grow out. However, once we reach the end of the window to apply Preflood N, it’s time to fertilize and begin putting on a shallow flood – chase the rice up as it grows. This is not an easy request, but this is how we maximize our yields and inputs – by being on time.
Some fields evaluated for lower than expected yields in 2015 were found to have been fertilized strictly by height. In those instances once the rice was flooded it was 8+ inches tall and it had 8+ leaves. This is not normal but by that time it had likely set most of its tillers and did not fully respond to preflood nitrogen fertilization. We must attempt to stay on time, by growth stage and DD50 unit accumulation, if we want to maximize yield and profitability in 2016. Try to be on time with Plan A, then go to a Plan B once that option runs out.
Weed Control Issues
Overall rice weed control looks outstanding. A lot of overlapping residual treatments have kept us very clean with many fields going to flood now.
Starting to see a few more fields with Newpath drift. Most will unfortunately take weeks to recover unless we get some sunshine and warmer temperatures soon.
Also getting calls on drift of Dual, Zidua, and Boundary. Most of these only cause stunting and slight delay in maturity or rice. Boundary can cause more damage because of the Metribuzin component.
Gramoxone drift from minor to severe. Most will be ok if new leaf is coming out green.
A few calls on ALS-resistant sedges, recommending Basagran + Propanil. See the fact sheet:
Fig. 1. Newpath injury on conventional XL753 is usually easy to spot due to scattered Clearfield plans.
Fig. 2. Gramoxone burn with new green leaf emerging (also Command injury).
We have several fields this week that were treated with NipsIt or CruiserMaxx that are having problems with Grape Colaspis (GC) or lespedeza worm. In all cases, the field had been planted 40+ days ago and in some cases over 60 days and now the GC’s are becoming active and moving up into the rooting zone and causing the symptomology in Fig. 3.
Many people may be confusing this symptomology with their herbicide application or salt injury or seedling disease. The field in the pictures was running about one GC per 2 inches of row. That’s more than enough to cause damage to the rice. The most we can expect from seed treatments is about 28-35 days at best, particularly in a wet spring. This is why we warned you previously about fields going to flood and the lack of control you will see with rice water weevil.
We are currently looking at seed treatments with a combination of products to see if we can help with this issue in the future. But for now, all you need to know is that if you are 40+ days after planting and are seeing GC issues the standard recommendation is to fertilize with nitrogen and flush the field if the rice is small, or try to get to flood if the rice is larger. Hopefully, this will help stimulate root growth and outrun the GC’s. Call if you have any questions.
Fig. 3. Slightly discolored rice with Grape Colaspis feeding on roots.
Tips for Multiple Inlet Rice Irrigation
Many questions these days about how to get MIRI right. Find tips here: http://www.uaex.edu/farm‑ranch/crops‑commercial‑horticulture/rice/2016%20Tips%20for%20Multiple%20Inlet%20Rice%20Irrigation.pdf.
DD50 Program is Up and Running!
The DD50 program can be found at http://DD50.uaex.edu. Enroll fields now to help with timing most major rice management practices.
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