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Agronomy Update: Corn Rootworm Pressure; Be Safe this Fall

Corn Rootworm “Rewind”

Below is a recap of our July 22 agronomy newsletter article about corn rootworm (CRW). We acknowledged the historically low CRW populations of the past few seasons in that article. But as the summer of 2020 has progressed, many areas are observing a surge in corn rootworm population. Some agency/university reports double population numbers, but this still keeps them near or below the 0.75 beetle per plant threshold on average. Time will tell if this uptick is a long-term trend or a cyclical surge.

As you evaluate your 2020 crop and look to 2021, keep CRW control in your mind. The pressure is still there and hotspots occur! Crop rotation is our friend in very high-pressure areas, but we continue to see excellent control from our CRW corn hybrids. Be sure to get a close look at our Qrome®, Optimum® AcreMax® Xtreme, or SmartStax® hybrids this fall. Get out there and scout!

From the July 22, 2020 Newsletter:

Corn rootworm (CRW) larvae should be at, or just past, their peak feeding frenzy for the season, making it an ideal time to dust off the shovel and investigate any potential issues. Many universities and state agencies track CRW populations over time and most show that Midwest numbers are the lowest in 10 to 15 years, likely due to the widespread implementation of Bt traits. However, hotspots do occur with damaging consequences, so we need to monitor field conditions closely to properly manage the pest in the moment and in the future.

July: First, if you are just entering pollination, watch for silk feeding. If beetles are clipping silks back to less than a half inch and much of pollinating still remains, consider a treatment.

Next, we need to inspect roots for signs of larval feeding, ideally from mid-July to mid-August. Pruned brace roots will appear ragged and off color while healthy roots are white. The NIS rating system developed at Iowa State University is often used to assess CRW pressure and Bt trait use and effectiveness. You might see a score that looks like 1.75. This means that 1 node was completely pruned while the next was 75 percent pruned. A root is considered pruned if it has been consumed to a length less than 1.5”. A NIS score of greater than 0.75 typically leads to economic yield loss.

For August/September: Root assessments are mostly post-mortem at this point, but will be important for future planning when combined with knowledge of beetle presence during August. Conveniently, we want to watch for more than 0.75 beetles per corn plant in August. Areas that experience ‘rotation resistant’ populations will need to get sticky traps into their soybean fields too.

Safety:  The Safe Way Versus The Quick Way

With the 2020 harvest season upon us, remember to take time to think about the safe way to work or do a job. During harvest season, we may be running on less sleep, running on less than ideal nutrition, and pushing hard to get a crop in before inclement weather hits and stops us. Amidst all these stresses, we need to remind ourselves, our family, and employees to do the job the safe way.

We have all done many of the jobs that need to be done ahead of, during, or after harvest, numerous times. We all know the best, safe way to do a job, and then we also know a short cut or two that is quick. And, we have done it that “quick way” countless times. The issue is the “quick way” may not always be the safest way, 99 percent of the time the “quick way” works; however, that 1 percent of the time could lead to an accident or worse.

Lastly, remember by doing it safely you are setting an example of how to do a job correctly. Others may watch how you do things -- it could be your spouse, your children, your grandchildren or an employee. Set a good example and do it safely.

Labor Day

Due to next week’s Labor Day Holiday, Dairyland Seed will not have an agronomy newsletter to share. The Agronomy Team will return with a newsletter the week of September 14.

We’d like to thank all of the men and women who work tirelessly to provide food for your community and for our country. Wishing you and your family a safe and fun Labor Day!

Corteva Technology Use Agreements

All growers with orders for any Corteva Agriscience brand seed product, regardless of crop or trait (including non-GM products) need to have a signed Corteva Technology Use Agreement in place by September 1. Growers should sign the Corteva Technology Use Agreement electronically at Signing electronically is preferable, however, paper copies are available at

Brian Weller
Brian Weller
Western Region
Dan Ritter
Central Region
Branden Furseth
Northern Region
Rod King
Eastern Region
Terry Jones
Eastern Region
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