Specialists
Speaking
Disease and insect pests
the fungicide application. For blast and the smuts (kernel smut and false smut), they occur in a manner that prevents us from using thresholds. We’re forced to treat for these preventatively. In fields with a history of these diseases, avoid susceptible cultivars and excess nitrogen applications. For blast, maintaining an adequate flood depth is critical. Susceptible cultivars grown in fields with a history of these diseases may be candidates for preventative treatment. Rice stink bugs are certainly an annual issue, but we never know what we’re going to get. The most important consideration for this year will likely be the point at which we can safely stop treating for stink bugs. When 60% of the kernels on panicles have reached the hard dough stage (straw-colored kernels), and rice stink bugs are below treatment thresholds, we can stop treating for the pest. As a reminder, the threshold is 5 stink bugs per 10 sweeps the first two weeks of heading and 10 stink bugs per 10 sweeps the second two weeks of heading. Hopefully, we deal with a below average pest management season in 2022. Contact your county Extension agent or a specialist if we can help.
DR. JARROD HARDKE ARKANSAS Professor/Rice Extension Agronomist University of Arkansas Cooperative Extension Service jhardke@uada.edu Every season, the situation for disease and insects in rice is entirely different. Each is influenced greatly by environmental conditions, but they’re always there looking to take a bite out of our bottom line. The 2022 season and its rising input costs scream this is the time to follow integrated pest management practices. This means we need to use scouting and thresholds to determine whether it’s economically in our best interests to act. Let’s start with sheath blight, arguably our No. 1 disease in rice. Other diseases can cause greater direct losses, but we deal with sheath blight on a more regular basis. Finding sheath blight in a field does not mean we should treat for it. Use a threshold to determine when to treat based on cultivar susceptibility, frequency of distribution and height in the plant canopy. For moderately susceptible cultivars, when greater than 50% of field stops are positive for sheath blight, or for susceptible cultivars when greater than 35% of field stops are positive, treatment may be warranted. That covers the cultivar susceptibility and the frequency of distribution. The final condition is height in the canopy. Even if we meet the previous two criteria to consider treating, we need to evaluate how high in the canopy sheath blight has progressed. Our goal is to reach 50% heading with the upper three leaves in the canopy clean to outrun yield loss. If sheath blight is present at above-threshold levels, we need to keep a very close eye on it. If it is staying low in the canopy, we can delay treatment and hopefully outrun it, which will save us
Sheath blight issues in furrow-irrigated rice DR. JUSTIN CHLAPECKA
BRANTLEE SPAKES RICHTER, UNIVERSITY OF FLORIDA, BUGWOOD.ORG
MISSOURI Assistant Research Professor/ Rice Extension Specialist University of Missouri jchlapecka@missouri.edu
The threshold for rice stink bugs is 5 stink bugs per 10 sweeps the first two weeks of heading and 10 stink bugs per 10 sweeps the second two weeks of heading.
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RICE FARMING
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MAY 2022
The time we’ve all been waiting for is finally here. I opened with that line last month, and it appears I was wrong. Writing this at the end of April, we MIGHT be 1% planted in Missouri and that’s being hopeful. A few dry days to close out the month have been much needed, and some of the lighter ground is finally planted. Hopefully, by the time you’re reading this, we have some real rice acreage in the ground. If not, we’ll be looking at even more of a reduction in rice acreage for 2022. Caused by the fungus Rhizoctonia solani, sheath blight has been an issue in furrow-irrigated rice. The mindset of most experts four or five years ago was that it would be much less of a problem in furrow-irrigated rice. It’s safe to say we got that one wrong. While there is not a flood to float inoculum into contact with the sheaths, the disease inoculum is still present in the field. Reports from farmers and consultants indicate that sheath blight is a much more common problem in furrow-irrigated rice than we would have thought. In fact, the largest issue is at the top of the field. Now let’s dive into that issue. While the sclerotia float and infect the plant at the water line in flooded rice, it can start at the soil line where a flood is not held. Also, keep in mind the furrows do hold water for a significant period of time. Once infection occurs in furrow-irrigated rice, it may be more likely to spread due to slightly higher nitrogen rates and increased RICEFARMING.COM
