August 8, 2014 No. 2014-22
Dr. Jarrod Hardke, Dr. Gus Lorenz, and Dr. Yeshi Wamishe
Rice fields are actually being drained. It has taken us seemingly forever to get to this point, but here we are. Plenty of fields still have a long way to go (Table 1), but it’s still a good feeling to start turning the page. Rice in the state currently ranges from recently going to flood all the way to draining – no word of harvested rice just yet, but it won’t be long now.
Table 1. Percent of rice acres set to reach harvest moisture during listed weeks of 2014 according to DD50 enrollment.
The 10 day forecast calls for continued mild conditions in the 80s and low 90s with regular chances for rainfall. Overcast conditions are not what the doctor ordered for a speedy grain fill, but mild conditions are. Let’s hope we don’t get much impact on flowering and pollination. Disease will definitely be a concern – these conditions are a recipe for disease progress so keep scouting those fields and make preventative applications for blast and smuts. The rule for the season has been to expect the unexpected, so be ready for that forecast to change quickly and adjust accordingly.
The majority of complaints continue to be a combination of unevenness in heading and general heading delays – y’know, weather problems. So let’s talk weather and heat units.
Focusing on March 16 – July 31, let’s look all the way back to 1983 for DD50 unit data. Over that period this year we’ve accumulated 2,700 heat units compared to 2,717 last year. Have we ever had fewer than this year? Yes, in 1983, 1989, 1990, and 1997. So really it’s just been a while (’89-’90) since we’ve had back-to-back years like this. Table 2 shows how we accumulated DD50 units in ’89-’90 and ’13-’14. As you can see, we’ve done this dance before.
Table 2. Cumulative DD50 units by month for 1989, 1990, 2013, & 2014.
Out Standing in Your Field
Disease is Everywhere
Symptoms of collar blast (Picture 1), panicle blast (Picture 2), and neck blast (Picture 3) have started to show up in a few varieties including Roy J, CL261, and Caffey. Remember the blast pathogen attacks leaves, nodes, the collar, the neck, and panicles of rice plants. Neck blast is the worst of all, potentially causing 100% yield loss when not managed with properly timed fungicide applications.
Collar blast largely dries out the flag leaf that is responsible for more than 75% of grain fill. Panicle blast dries panicle branches resulting in death of florets. Node blast occurs at stem joints and makes the crop susceptible to lodging. Neck blast rots the panicle neck resulting in an upright blank panicle.
Overall, this week appeared to slow blast disease development compared to previous weeks. Leaf blast (Picture 4) still prevails in several fields. Remember if the weather changes to favor the disease, it remains of concern especially in late rice. The rain across the state in the next few days may keep the plant tissue wet for a long time. Continue being alert…
Sheath blight has been moving relatively slower than the previous weeks. Again, weather matters.
False smut has started showing up this week. The weather has been favorable for the pathogen to infect and progress. Fields with history, high nitrogen fertilizer rates, and planted to susceptible cultivars are prone to false smut. False smut pathogen is favored by cooler temperatures than kernel smut. Both smuts are suppressed by triazole fungicides applied with a minimum of 6 oz/acre rate (Tilt equivalent) at the correct timing. Remember early boot to full boot is the right timing. Boot split and beyond is too late for fungicide application to suppress either false smut of kernel smut. Kernel smut is more sensitive to fungicides than false smut.
So far, samples received suspected of bacterial panicle blight have not tested positive. A few panicles from inoculated test plots have shown the typical symptom (Picture 5). The weather this year so far does not fit those years of severe BPB that were hot with extended hot nights. It is likely that BPB will remain light this year. Remember BPB symptoms can be confused with symptoms caused by several environmental factors. Rice plants damaged by stem borer also show similar symptoms. So far, there are no chemical options for management of BPB in rice.
Rice stink bugs are still out there, but at this point they seem to be pretty spread out. A few other pests you may encounter in the field are blister beetles and billbugs.
Blister beetles (Picture 6) are found in groups, sometimes in seemingly large numbers, but are generally nothing much to worry about. They will feed a little on leaf tissue and move on. But don’t mess with them – make the mistake of walking through a group of them at your own peril – they’re called blister beetles for a reason.
Rice billbug larvae (Picture 7) can be found in rice plant stems near the base of the plant. These will usually be found in plants on levees and when severe can make keeping a stand on levees difficult. With more acres being with furrow irrigation, potential billbug problems are much greater.
Enroll fields in the DD50 Program here: http://DD50.uaex.edu.
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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.