July 12, 2013 No. 2013-16
Dr. Jarrod Hardke, Dr. Gus Lorenz, and Dr. Yeshi Wamishe
The majority of midseason fertilizer applications have now gone out on rice up and down the state. DD50 numbers indicate that over 90% of the crop is beyond ½” internode elongation. The earliest planted rice fields should have begun to head this week with a larger portion starting next week. Many growers are preparing for fungicide applications for smut suppression and sheath blight control.
I have received a few questions about rice fields not matching up exactly with DD50 numbers. Remember the DD50 is a projection/predictor of when the crop will reach certain stages. This is based on average values across years of research – so we will see fields that vary somewhat from the DD50 projection. However, this variation shouldn’t be more than a couple of days. This has been a strange year weather-wise, but the DD50 prediction should still be pretty accurate.
While the humidity is expected to be lower over the next several days, it will return early next week. Temperatures are expected to remain in the low to mid-90s and lows should stay below 75. This will be ideal in terms of helping us to maximize heat units for crop progression while minimizing stress from extremely high day and nighttime temps.
Favorable conditions seem to be shifting DD50 estimates earlier now as we maximize heat units and increased DD50 program enrollment improves the accuracy of these numbers (Tables 1-3).
Tables – Percent of rice acres to reach growth stages during listed weeks of 2013 according to current DD50 enrollment.
|Table 1. 1/2″ IE||Table 2. 50% Heading||Table 3. 20% Grain Moisture|
|1/2″ IE Date||Percent||50% Heading Date||Percent||Harvest Date||Percent|
|Reached ½” IE||93%||50% Headed||17%||Aug 10-16||13%|
|July 13-19||5%||July 12-18||28%||Aug 17-23||23%|
|July 20-26||2%||July 19-25||24%||Aug 24-30||24%|
|July 26 – Aug 1||17%||Aug 31 – Sept 6||21%|
|Aug 2-8||10%||Sept 7-13||12%|
|Aug 9-15||3%||Sept 14-20||5%|
|Aug 16-22||1%||Sept 21-27||2%|
Out Standing in Your Rice Field
Rice Stink Bug
The first fields should be beginning to head this week and picking up next week. Rice stink bug (RSB) adults can be found everywhere on headed grasses and even lurking in rice fields that have yet to head (Pictures 1 & 2). Let’s be prepared to start scouting as rice reaches 50% heading.
We have also noticed a large number of beneficial insects in fields – these will help to suppress rice stink bug populations. So, focus on scouting (early morning for best results) and reaching treatment thresholds:
First 2 weeks of panicle emergence – treat when you average 5 RSB per 10 sweeps.
After the first 2 weeks of panicle emergence – treat when you average 10 RSB per 10 sweeps.
Currently recommended products for RSB control are Sevin, malathion, Prolex, Karate Z, and Mustang Max (always read and follow the label).
If we jump the gun and spray too early – we may guarantee an additional application because we’ve taken out all of our beneficial insects early and RSB will return. DO NOT just throw an insecticide in the tank when making pre-heading fungicide applications – you just might cause a stink bug problem. If stink bugs are bad enough, you might have to make two applications anyway, but if you spray too early, it might mean you need three for the year. Thresholds are in place to save you money, so let’s not waste an application.
Picture 1. Rice stink bugs on headed grass in a pre-heading rice field.
Picture 2. Rice stink bug basking in the evening sun on pre-heading rice.
If you haven’t been worried about disease, now is the time.
Sheath blight – only isolated reports so far, nothing widespread. Remember that if warm, humid conditions continue this disease can move fast.
Blast – again, only isolated reports, but it is out there. Keep the flood depth at 4 inches or more. If forced to treat – timing is critical to avoid yield loss from neck blast. For two applications – the first needs to be at late boot and the second when heads are 2/3 out on main tillers. For a single application – at least 1/3 of the panicle still needs to be in the boot or the fungicide won’t be as effective.
Picture 3. Typical blast lesion.
Smut – we can only protect our crop from kernel smut and false smut. Fungicides suppress these diseases when applied early, but cannot control them if we wait too late. Treat with at least 5.5 to 6 fl oz per acre of Tilt. 19 oz of Stratego has 5.5 oz of Tilt, 21 oz of Quilt Xcel has 6.2 oz of Tilt, and 20 oz of Quilt has 5.8 oz of Tilt. Treat early to mid-boot BUT BEFORE HEADS EMERGE. Once heads have emerged it is too late and we can keep the fungicide in the jug.
Picture 4. Once heads are emerging from the boot – it’s too late to spray for smut suppression.
Need Help with DD50 Enrollment? Call or E-mail Me or Your Local County Extension Agent
If you prefer to enter them yourself, please visit http://dd50.uaex.edu/dd50Logon.asp.
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We sincerely appreciate the support provided by the Arkansas Rice Research and Promotion Board for this publication.
The authors greatly appreciate the feedback and contributions of all growers, county agents, consultants, and rice industry stakeholders.