Arkansas Rice: Harvest Approaching, Management Options for Rice Stink Bugs

Rice Stink Bug

We’re looking at an unsettled weather pattern for the upcoming week which may be a welcome turn for those tiring of season-long irrigation efforts, but ill timed for others.  The earliest fields that have already been drained should be about ready for harvest to begin next week, and potential scattered storms could certainly put a damper on getting started.

We’re at that stage where we want clean, clear, warm weather to finish up the crop and get it out under drier conditions.  The possibilities of scattered storms and the beginning of activity in the Gulf are some causes for concern.  But beyond a few days out there’s little to be confident in with our weather predictions this year, so it’s more of a “stay tuned” situation.

The upside is that conditions are still expected to stay fairly warm (if you believe the long-term forecast) which is really good considering half the crop was planted in May and June.  This will hopefully set us up to finish up with solid yields on the later acres.

One thing to keep in mind is that some of the odd weather and temperature occurrences from earlier in the year have further bunched together the crop, meaning that once we get rolling in harvest, even seemingly spread out planting dates are going to get ready a lot closer together.  Be prepared to hammer down as soon as the opportunity presents itself as you likely won’t need to check up for anything but weather.

Rice Stink Bug Management and Current Options

We have had numerous phone calls over the past three weeks about rice stink bug control failures with lambda (Warrior II, Kendo, Lambda-Cy, Silencer, etc.). Before we go into what we are currently observing in the field, we need to address what constitutes a control failure.

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Nymphs, or the immature stage of rice stink bugs, is what we are keying on to determine if we have had a control failure.  If we find large nymphs (cream colored) within 7 days of the application, then there is a good chance those nymphs were present or eggs were laid shortly after the application was made.  If you are only finding adults then these are most likely new adults that have migrated into the field.

In our studies we sampled this week, we were only able to achieve 26-61% control of rice stink bug nymphs with a 1X rate of lambda (3.65 oz Lambda Cy) with an average control level of 50%.  The reports we are receiving from growers and consultants are similar to the results we are seeing, with some cases being complete misses, with no change in the nymph population at 5 days after treatment.

As of today (8/13), Arkansas has received approval for the use of Endigo ZC for use in rice.  This approval expires on Aug. 27th.  The recommended use rate range is 4.5-6.0 oz/acre and there is a 21-day pre-harvest interval (PHI).

Users must report applications of Endigo ZC to rice to the Arkansas Department of Agriculture within 10 days of application.  The label and forms required for applications will be available on the Arkansas State Plant Board website.

The last thing I we want to mention is when can we terminate rice stink bug applications.  We have done quite a bit of work on this and have determined that when we hit 60% straw-colored kernels on a panicle we can terminate rice stink bug applications.  We do want to be pretty clean going into 60% straw coloration, because at high populations of rice stink bugs some damage can occur after 60% straw-colored kernels.

The only time we would not recommend terminating at 60% is if we have several days of rain in the forecast.  This can soften kernels and make it easier for rice stink bugs to damage kernels that would otherwise be past the point of receiving damage from rice stink bugs.  Good luck finishing out this crop, and feel free to call us with any questions.

Cercospora – Narrow Brown Leaf Spot (NBLS)

Late season Cercospora was probably more responsible for some yields being off than many realize.  However, so far this year very little has been observed.  Unfortunately, Cercospora can sometimes show up late and only fungicide apps at the kernel or false smut timings prevent it.

Given the upcoming forecast and possible conditions on some of this later rice, it’s better to think through field histories on whether a fungicide application may be needed for protection.

If treatment is required, go with a triazole (such as Tilt).  The later the rice is planted, the more it could possibly benefit from a fungicide application.  The later the planting date, the earlier in rice growth Tilt should be applied.

For example, Tilt can start being applied at 1/2” IE to prevent Cercospora.  Rates of Tilt may have to lean higher than the 6 oz rate we more commonly use; instead, 8-10 oz may be needed for proper management of NBLS.

Cercospora sprayed versus unsprayed

Propiconazole sprayed strip at booting (left) and untreated strip (right) at LSU. Courtesy Dr. Don Groth.




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