Sunday, September 19, 2021

Arkansas receives temporary approval for rice stink bug material

• By Nick Bateman •

rice stink bug adult
Rice stink bug adult — photo by Vicky Boyd

As of Aug. 13, Arkansas has received approval for use of Endigo ZC to control rice stink bugs in rice. This approval expires Aug. 27.

The recommended use rate range is 4.5-6.0 oz/acre, and there is a 21-day pre-harvest interval. Users must report applications of Endigo ZC to rice to the Arkansas Department of Agriculture within 10 days of application.

Endigo ZC from Syngenta is a premix of lambda-cyhalothrin and thiamethoxam.

The label and forms required for applications are available for download on the Arkansas State Plant Board website.

What is control failure?

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.

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 seven 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%  to 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. Some cases were complete misses, with no change in the nymph population at five days after treatment.

When to terminate stink bug treatment

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 rice stink bug populations 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.

Dr. Nick Bateman is a University of Arkansas Extension entomologist. He may be reached at nbateman@uada.edu.

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