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Arkansas Rice: Be on Lookout for Black Cutworms; Resistant Barnyardgrass on the Rise

Ernst Undesser
By Jarrod Hardke, Bob Scott, and Jason Norsworthy, University of Arkansas April 17, 2017

Arkansas Rice: Be on Lookout for Black Cutworms; Resistant Barnyardgrass on the Rise

Photo from Mississippi State University

Rice planting has been rocking and rolling as much of the state missed predicted rainfall this week.  We could end up close to 60% planted by the time rainfall is expected on Monday and Tuesday.

Due to the warm, dry conditions a number of fields have been receiving the dreaded flush.  However, with the crusting issues and lack of herbicide activation it could be the best money spent all year.  Farm like it’s never going to rain again is the mantra heard lately.

If you wait until next week’s forecast rain and you miss it, it may be too late to salvage the stand.  Nobody needs that kind of setback this year.

Fig. 1. Weekly planting progress, 2012-2017, USDA-NASS. Click Image to Enlarge

Fig. 2. Fields have been very busy this week with favorable conditions.

Black Cutworms Eating Emerging Rice in Southeast Arkansas

Black cutworms have been found feeding on emerging rice and cutting the plants back to the soil.  We don’t yet know how widespread this problem is – the first report was received tonight.  Hopefully it’s a pretty isolated incident.

However, they can be very difficult to see, and they like to hide under clods during the daytime when it’s hot.  If you see any stand issues inspect the plants and ground closely for larvae and an insecticide application may be needed to protect and preserve the stand.

Fig. 3. Black cutworm larva.

Fig. 4. Black cutworm larvae can be difficult to see especially on a rough soil surface.

Don’t Bust the Budget on a Mistake

Soil test based fertility recommendations are there to maximize your return on investment based on university research.  When these aren’t followed the sting can be substantial.

Herbicide Resistance Info


Just this week a conversation turned to a field that soil tests called for virtually no fertility – all categories were Optimum or Above Optimum, except needing a little zinc.  The recommendation would have been to apply a form of zinc at planting only to address this single problem and move on.

What happened was that a fertilizer blend plus 100 lbs urea was applied at planting.  This means over $40 per acre was spent and very little of what was applied was needed at all.  The urea in particular will be an almost complete waste as it will be weeks before the plant will be capable of taking up any N from it and by then almost all of it will be gone.  We do not recommend nitrogen applications at planting.  They are too inefficient.

There was nothing wrong with the blend application other than a lot more was paid for and put out than was needed.  Definitely spend where you need to spend, but this is not a year for the ‘bonus applications’.

2015 and 2016 Resistance Samples Reveal Alarming Trend

Prior to 2010, most barnyardgrass samples that were sent in to our testing program came back positive for propanil and Facet resistance.  Although we had found resistance to the ALS herbicides (Newpath, Regiment, Grasp, Beyond) and the ACCase herbicides (Clincher/Ricestar), it was rare.

This all began to change when samples came in from trouble fields in 2012 as we began to see an upturn in samples resistant to these classes of chemistry and added two more Command-resistant sites.  This was also the time when we first started to document a number of fields with resistance to multiple groups of chemistry, even 3- and 4-way resistance.

Below are graphs showing the percent (%) of samples from 2006-2012 and from 2015-2016 that tested positive for resistance to the herbicides listed.  The trend for resistance in both the ALS and ACCase classes continues to increase from almost none in 2011 to 5 and 12%, respectively, in 2012 to 27 and 46%, respectively, in 2015/16 samples.  It is important to keep in mind that these are weighted samples in that they come from fields where barnyardgrass was difficult to control.

Click Image to Enlarge

Click Image to Enlarge

The Herbicide-Resistant Weed Information Sheet is a form that can be used to send in suspected resistant barnyardgrass for testing, this service is provided at no charge through a grant from your check-off dollars from the Arkansas Rice Research & Promotion Board.  This support is greatly appreciated.

To fight herbicide resistance we recommend sampling your fields in the fall to determine what herbicides will be effective the following year and building an overlapping residual program based on the results of the resistant tests.  For more information contact your county office.

Enroll Fields in the DD50 Program to Help Time Management Decisions

The variability in environmental conditions the past few seasons has shown the importance of managing the rice crop on time.  The DD50 Rice Management Program helps to predict the timing of the most critical practices to make sure we hit our marks and produce the best crop that the environment allows.

The DD50 program can be found here.  The program is now much friendlier for mobile use than in the past and efforts are underway to further improve functionality for future seasons.  Please let us know if you have any questions or encounter any problems.


Source: : http://www.arkansas-crops.com/2017/04/14/arkansas-rice-update-14-17/

Ernst Undesser
By Jarrod Hardke, Bob Scott, and Jason Norsworthy, University of Arkansas April 17, 2017