Arkansas Rice: Managing Stink Bugs in Late Fields, Weeds on Prevented Plant Ground

Rice Stink Bug

Application Timing for Rice Stink Bug in Late Rice

Over the past week we have gotten multiple calls about some growers not wanting to spray for rice stink bug in their late rice. This is understandable, we have spent a lot of money this year already to get the crop to where it is. We should keep in mind that our late rice is going to have high rice stink bug populations, and that the higher these populations are the greater the chance of having ‘pecky’ rice. Most mills do not dock for 2% peck or less, but starting at 2.5% we can see a loss of $30 an acres on 200 bushel rice.

With this in mind, the question becomes: If I can only make one application for rice stink bug, what timing gets me the most bang for my buck?

Based on our work the past few years, an application around 50% milk and 50% soft dough gives us the best chance of reducing peck. This is not a suggestion for an automatic application, but rather if I can only make one application this is the timing I would choose. This application timing has also shown increases in total rice, which can help maintain profitability. We have a lot of confidence in our current thresholds for rice stink bug, and would like to see rice stink bugs managed by those guidelines.

Rice stink bug management is not an area where money should be saved on our late rice. At a minimum we are looking at one application, but most likely more. If we are only willing to make one application, we should time that application when rice panicles are around 50% milk and 50% soft dough.

Residuals for Weed Control on PP Ground

On the ~1 million acres of prevented plant (PP) ground this year in Arkansas, managing weeds has become a priority to reduce seeds from returning to the seedbank. End-of-summer/fallapplied residual herbicides are a great option to stop more flushes of weeds from emerging and save us from extra postemergence applications.

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However, later applied residual herbicides have the potential for carryover into our next cropping season, which may severely impact our crop potential. Here’s a few things to keep in mind if applying residual herbicides on PP ground and rotating to rice next season:

1. Many residual herbicides have plantback intervals to rice at or greater than 8 months. Therefore, there are limited options to apply at this time to remain on-label.

2. Beware of drifting these late-applied herbicides onto neighboring crops that may be finishing up. A lot of crops are at a delicate stage with grain-fill and even a slight drift amount can significantly impact yield.

3. Herbicide carryover is a guessing game in most situations (dependent on environment, soil, precipitation, etc.). Although certain residual products may be successful 4 out of 5
years and not result in crop injury, those same herbicides may significantly damage the crop the other year.

Residual herbicides that can be used, used with caution, or should not be used for PP ground rotating to rice are as follows:

Can use: Sharpen, Prowl, Verdict (10 fl oz/ac max), Valor;
Use with caution: Dual Magnum, Outlook, Callisto, Treflan;
Do not use: atrazine (if applied after June 10, only corn or sorghum can be planted FY), metribuzin especially in a high pH soil, Zidua.

These residual herbicides should also be selected depending on the target weed species and timing. If applications are planning to go out now to manage late flushes of Palmer amaranth, PPO-inhibitors (Valor, Sharpen), Group 15’s (Dual Magnum, Outlook), Verdict, and Callisto would work well. If the primary concern is grasses, especially ryegrass later this fall, applications of Prowl, Treflan, and Group 15’s (Dual Magnum, Outlook) will help.

However, the later applications get delayed into the fall, the greater potential for crop injury to occur. A study from Mississippi State showed crop injury, stand loss, delay to 50% heading, and yield loss from fall applications of Dual Magnum, Zidua, and Treflan. Their study had approximately a 6 month gap between applications and rice seeding (sprayed in November, planted in May), and was conducted on a heavy Sharkey clay soil with high pH (8.0 – 8.2). Therefore, the potential for injury in Arkansas on lighter soils, especially those which also have a high pH, is greater than what was documented in the Mississippi study.

Although residual herbicides are a great option for weed control on PP ground, implementing tillage where possible is also still beneficial without a risk of crop injury the following year. In the war against weeds, keep fighting the good fight out there.


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