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18
Jul
2013
Arkansas Rice Update 7-18-13
Author: Jarrod Hardke, Rice Extension Agronomist

July 18, 2013                              No. 2013-17

Dr. Jarrod Hardke, Dr. Gus Lorenz, Dr. Bob Scott, and Dr. Yeshi Wamishe

Crop Progress

Finally, (almost) all rice in the state is beyond ½” internode elongation.  By the end of the week, nearly half of the rice acreage should be reaching 50% heading.  The majority should follow in the next three weeks with the latest planted fields getting there about mid-August.

The point at which fields are projected to reach 20% grain moisture for harvest is spread out to say the least.  The first fields should get there the first week of August, but the last fields won’t until late September or early October.  Say it with me now, “NO EARLY COOL SPELL.”  Maybe if we all say it enough it will happen.  Rain dances always worked because they wouldn’t stop dancing until it rained – maybe we’ll be more fortunate.

For now, warm temperatures in the low to mid-90s fill out the 10-day forecast.  Isolated thunderstorms are also a constant throughout the weekend and early next week.  I am still hoping our temps remain in that range throughout crop maturity to help us producer solid yields with no loss in grain quality.

With the rice crop beginning to head – be on the alert for rice stink bug infestations.  While blast and sheath blight reports have been low, keep an eye on these diseases as your crop begins to head so that fungicide applications can be appropriately timed.  More information on these topics on the following pages.

Tables – Percent of rice acres to reach growth stages during listed weeks of 2013 according to current DD50 enrollment.

Table 1. 50% Heading Table 2. 20% Grain   Moisture
50% Heading   Date Percent Harvest Date Percent
50% Headed 47% Aug 3-9 2%
July 19-25 23% Aug 10-16 13%
July 26 – Aug   1 16% Aug 17-23 23%
Aug 2-8 9% Aug 24-30 23%
Aug 9-15 3% Aug 31 – Sept 6 20%
Aug 16-22 2% Sept 7-13 11%
Sept 14-20 5%
Sept 21-27 2%
Sept 8 – Oct 4 1%

Out Standing in Your Rice Field

Rice Stink Bug

Early planted rice is beginning to head this past week and even more will be heading this week and next.  As expected rice stink bug numbers are extremely high in these fields.  With a threshold of 5 stink bugs per 10 sweeps, the question isn’t whether or not you’re at threshold but rather do I really need to count how many are in the net?  May sound silly to some but the answer is, yes, you need to count, so when you come back after application you can see how much control you were able to get.

Remember with numbers as high as this it may require 2 applications to achieve control.  If one shot does it that’s great, but you need to be prepared if one isn’t enough.  So remember, the threshold of 5 stink bugs per 10 sweeps the first two weeks of heading then dropping to 10 stink bugs per 10 sweeps the second two weeks of heading.

Choices on insecticides are Declare, Karate (lambda-cyhalothrin), Mustang Max, and Tenchu.  I expect these will be the most available.  We’ve tested all of these and found them to all be effective.  I don’t see any advantages of one over the other, so shop and get the best price.

One question I’ve received this past week on fields that have treatment level stink bugs but aren’t even heading:  Should I go ahead and spray?  NO.  If you spray before heading it’s no guarantee that you won’t have to spray again once the rice begins to head, because there is usually a big influx of stink bugs into the field at heading.  So you potentially just cost yourself another application.

The first two weeks of heading we are protecting yield potential so get out there and scout if you have rice beginning to head.

To Spray or Not to Spray

Plenty of questions lately about cleaning up escaped grasses in fields.  It all depends on crop progress and the size/stage of the weeds.  Take a look at the field in Picture 1 – are a few large grasses enough to warrant an application?  What about the field in Picture 2?

Picture 1.  Rice field with scattered large grass.

2013-17 Picture 1

Picture 2.  Rice field with a lot of large grasses.

2013-17 Picture 2

Herbicide applications such as Clincher + Facet or Ricestar HT + Facet are about $40-50/acre + application costs.  There are other products recommended to try and clean up large grass, but all will likely be in the same cost range.

So the question is – what’s worth it?  I find it hard to justify an application on that first field at ~$50/acre.  The second field seems much more obvious that an application is needed – but wait – what are you going to gain with that application?  Will it be cleaner?  Yes.  Will it help to reduce the amount of weed seed mixed in with your rice grain at harvest?  Yes.  Will it lead to a direct yield gain?  Probably not.  It may help prevent lodging though.

Weeds allowed to remain in the field much past flood have already caused yield loss by the time we get to where we are in the second field.  It is important to weigh the costs with the benefits.  The cost of the application should be equal to or less than the yield you hope to gain plus the mill dockage you save by keeping weed seed out of your rice.

Spraying very large weeds with many of our available herbicides will hurt those weeds and will likely kill a good number of them.  However, spraying weeds too large to kill is a good way to speed toward herbicide resistance to those products.

You probably remember seeing Picture 3 last week where we were talking about rice stink bug.  This week we show it to focus on the weed itself.  That is headed grass in a field.  You know what we call a herbicide application to kill headed grass like that?  Revenge.  It has already cost you yield.  It has already set seed.  A herbicide application at this point is about nothing more than revenge and will not provide any justifiable benefit – and will only expose that plant to a herbicide that could (possibly) pass on some level of herbicide tolerance to its offspring.

Late herbicide applications to clean up fields is a judgment call that should be made a on a field-by-field basis.  Spray because it will provide you with some benefit – don’t do it just to kill some weeds.

Picture 3.  Headed barnyardgrass in a pre-heading rice field.2013-17 Picture 3

Disease Notes

Sheath blight has been seen in a few more fields this week compared to last week.  Recent and forecasted rainfall may favor disease development.  Temperature and humidity are also high and there is a possibility for vertical movement of the disease.  Continue scouting until a few days before heading and make sure the top three leaves are free from the disease.  Research has indicated Stratego at 16 oz/A will give ~14 days of protection, at 19 oz/A will give ~21 days of protection.  Quadris at 6.4 oz/A will give ~14 days of protection, 8.5-9.2 oz/A will give ~21 days of protection, and the full 12.5 oz/A will give ~28 days of protection.  These are average figures and may change depending on field factors that affect the activity of the fungicide used.

Blast:  So far, there are reports of blast on Jupiter and CL151 in Woodruff County, on CL261 in Monroe County, and on Rex in Phillips County.  Fields that are susceptible to blast are those that are difficult to hold a flood.  Maintaining a deep flood of at least 4 inches after midseason will help reduce the risk of blast.  Scout fields close to tree lines more frequently.  Blast can appear in wide-open fields if other conditions are favorable (Picture 4).  Trifloxystrobin (GEM) is considered slightly more effective on blast than azoxystrobin (Quadris).  Repeated blast history in the field, susceptibility of the variety, high preflood nitrogen and lower flood depth in soil types that do not hold water should be taken as evidence for the need to scout for blast.

Picture 4.  Blast started at the edge of this field where water was very limited.2013-17 Picture 4

Autumn Decline:  We have heard good news from fields that followed the “drain and dry” strategy to rescue the rice crop that suffered from this black root rotting problem.  Rice plants in these fields started to grow new roots and greened up again showing normal appearance.  The culprit of this phenomenon is hydrogen sulfide toxicity.

We saw a field that shows a yellow cast similar to the symptom caused by autumn decline.  However, the rice plants on the levees are also yellowish, unlike the situation in autumn decline (Picture 5).  Although there is blackening of the roots and also crown rot to a certain level, nutrient deficiency, likely phosphorus and potassium, stands out.  Plants in greener spots of the field were shorter, brittle, and some leaves show bronzing, indicating phosphorus deficiency (Picture 6).  Brown spots in this particular case also could be an indicator for potassium deficiency.  Among other physiological advantages, phosphorus is essential for healthy root growth and potassium for general health of the crop.  The amount of brown spots on the leaves in this field is a good indicator that the crop is under stress – likely from nutrient deficiency.

Picture 5.  Yellow cast on the levee as in bay.2013-17 Picture 5

Picture 6.  Phosphorus deficiency symptoms.2013-17 Picture 6

Aug. 1 – Consultant Training / County Agent In-Service Training

Thursday, August 1, there will be a training session held for rice consultants and county extension agents working in rice.  This field-based training session will be held at the Rice Research and Extension Center near Stuttgart, AR.  Specialists slated to speak include Dr. Jarrod Hardke, Dr. Gus Lorenz, Dr. Karen Moldenhauer, Dr. Trent Roberts, Dr. Bob Scott, and Dr. Yeshi Wamishe.  Registration begins at 8:30 a.m. with field tours beginning at 9:00 a.m.  CCA credits will be available.  Further details will be sent out next week.  For more information please contact Dr. Chuck Wilson (cwilson@uaex.edu) or Dr. Jarrod Hardke (jhardke@uaex.edu).

Thursday, August 1, there will be a training session held for rice consultants and county extension agents working in rice.  This field-based training session will be held at the Rice Research and Extension Center near Stuttgart, AR.  Specialists slated to speak include Dr. Jarrod Hardke, Dr. Gus Lorenz, Dr. Karen Moldenhauer, Dr. Trent Roberts, Dr. Bob Scott, and Dr. Yeshi Wamishe.  Registration begins at 8:30 a.m. with field tours beginning at 9:00 a.m.  CCA credits will be available.  Further details will be sent out next week.  For more information please contact Dr. Chuck Wilson (cwilson@uaex.edu) or Dr. Jarrod Hardke (jhardke@uaex.edu).

 

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.

Additional Information

Arkansas Rice Updates are published periodically to provide timely information and recommendations for rice production in Arkansas.  If you would like to be added to this email list, please send your request to jhardke@uaex.edu.

This information will also be posted to the Arkansas Row Crops where additional information from Extension specialists can be found.  Please visit the blog at http://www.arkansas-crops.com/

Acknowledgements

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.


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