September 11, 2015 No. 2015-28
Dr. Jarrod Hardke and Dr. Gus Lorenz
Various rainfall amounts have hit most of the state over the past couple of days, slowing down harvest progress. Of greater concern is likely the temperature cooldown expected over this weekend that will slow rice needing finish maturing. We’re expected to warm back up some throughout next week with clear conditions until next weekend though, so things should pick back up.
The short story is that yields continue to be off 10-15% from last year. Where and when different cultivars were planted – or more specifically when they hit key reproductive stages – seems to have a lot to do with specific field performance. Conditions at certain key times during June and July seem to have caused serious fluctuations in panicle development around midseason and early boot.
If you look at the daily weather descriptions for locations in both north and south Arkansas you’ll see something interesting for June. During June when all of the rice currently harvested was reaching midseason, you’ll see that we had a grand total of around 6 days described as “clear” and that was about 1 day a week. Most of the rest of the days were rain, thunderstorms, or scattered clouds. Combine these conditions with strange temperature fluctuations and you have a recipe for impact on plant development.
Planting Date Study Results So Far
So, based on field observations and early plot harvest results, signs point to weather conditions as the culprit for our issues this year. How about a little data to back up that theory? You got it.
Looking at planting date study data collected so far at Stuttgart this year, there’s an interesting trend (Fig. 1). Similar planting dates are paired together for comparison between 2014 and 2015.
In 2014 yields were high early and increased in mid-April before beginning to fall in early May. Not out of the ordinary. But in 2015, yields started off substantially lower compared to 2014 followed by a significant drop in mid-April before rebounding to nearly equal the earliest planting date by early May.
Fig. 1. Average grain yield by planting date at RREC near Stuttgart, 2014-2015.
The harvest of more planting dates will help to paint an even better picture. However, the results of the May 5 planting date does give some hope that later plantings will improve compared to the mid-April plantings. Let’s continue to hope for the best while preparing for the worst.
Reports of “Pecky” Rice
Lately we have received calls about samples from fields with reports of “pecky” rice at 2-4%. Fields have been sprayed multiple times for rice stink bug control and thorough scouting records show stink bug populations were kept below threshold. So what gives? Not all pecky rice is the result of stink bug damage.
“Peck” has become the default term to describe damaged rice, but most associate the term directly with damage caused by rice stink bug. Unfortunately, in some years that association is not warranted – this year seems like that. Rice stink bug populations have not been that high this year compared to the past few years (when we didn’t have peck) for us to believe that all this damage is the result of rice stink bug damage.
A literature search shows that damage to rice kernels can be the result of many things, including heat, fungi, bacteria, and yes, rice stink bug. So the kneejerk reaction to associate all pecky rice with stink bugs isn’t accurate. At this point in time, most of the pecky rice reports are in the northern half of the stain where regular rainfall events have been common throughout the entire season including grain fill and drydown. It seems much more likely that environmental conditions conducive to fungal infection, water damage, and wind damage (bruising of kernels) is far more likely than stink bugs getting the best of us.
To many, getting hit with large amounts of damaged rice and the price dockage associated with it is just another punch in the gut for an already brutal year. Many are looking for someone or something to blame this season, but in reality, environmental factors seem most likely to blame, not a scout or consultant. We have treatment thresholds for a reason – spraying too much leads to reduced profitability, insecticide resistance, secondary insect problems, etc. The more common approach in recent years has become to treat as soon as stink bug numbers get close to thresholds with a fear of letting them get past us. It simply doesn’t make sense at this point for the reports of “peck” to be primarily rice stink bug. In the meantime we’ll keep looking and investigating what’s going on.
Fig. 2. Brown rice kernels (top) with many types of damage evident compared to undamaged brown rice kernels (bottom).
Fig. 3. Milled rice kernels (top) showing nondescript damage symptoms compared to undamaged milled rice kernels (bottom).
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We sincerely appreciate the support for this publication provided by the rice farmers of Arkansas and administered by the Arkansas Rice Research and Promotion Board.
The authors greatly appreciate the feedback and contributions of all growers, county agents, consultants, and rice industry stakeholders.