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Iowa State University Extension
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Extension Crop Update
This newsletter, and previous issues from recent years, can be found on-line at:  
http://www.extension.iastate.edu/plymouth/info/cropupdate.htm
August 17, 2017
Volume 20, Issue #11
Prepared by
Joel DeJong,
Extension Field Agronomist
Click on photo for contact info
Recent rainfall certainly helped the areas of NW Iowa that were really short. I suspect soybeans will benefit the most as we are entering the pod filling stage. I also think recent rainfall helped increase the kernel size, and therefore yield, of the corn crop. For those in really dry neighborhoods thinking about cutting silage, this rainfall might have increased the uptake of nitrate, so the nitrate content of corn plants might become a problem. Don’t forget ISU Extension & Outreach’s Drought Web Page, and in particular the “Nitrate Toxicity” publication on the Iowa Beef Center drought site. Here is a map showing the percent of normal rainfall for this region for the last 90 days from http://water.weather.gov/precip/:
Note that most of the region, because of recent rainfall events, at least has climbed back over the 50% of normal threshold. However, the most recent drought monitor reflects the areas of Iowa that still have concerns:

Palmer Amaranth – thanks to the diligence of a farmer and his local agronomist, an odd-looking plant in an Osceola County soybean field was positively identified as being Palmer Amaranth. It was destroyed, which I think is very important to reduce the risk of future plants becoming established. Although we would have rather identified them before they start growing seed heads, it is much easier to get a positive identification on them now when the seed head is present. Look for amaranth plants that have at least a few leaflets with petioles (stems) longer than the leaflet itself, and bracts below the seeds that are significantly longer than the seed. Great identification assistance can be found here.

Cover Crops: We are approaching the time when people are thinking about cover crops. Iowa Learning Farms has a Cover Crop Resources web page that supplies quite a bit of information about establishment. On that page there is a link to a short document titled “Cover Crops in Iowa: A quick Guide,” along with many other resources. The Midwest Cover Crops Council is another great web page. I particularly like the “Cover Crop Decision Tool” for deciding what works where you live.

Soybean aphids: There have been some fields in NW Iowa that reached the threshold for treating recently, but certainly not all fields. I have seen many fields reaching the R-5 stage, and a couple with early varieties getting close to R-6. Review staging here. ISU research shows there is no benefit treating for aphids when we get to R6, and there is some debate about treating after R5.5. If we are just getting to R5 (1/8-inch seed in the most mature pod on the top 4 nodes) it takes 15 days to get to R6 (full size seed in pod in the most mature seed on the top 4 nodes). Remember, the economic threshold for treatment is 250 aphids per plant, more than 80% of the plants infested and aphid populations on the increase.

Dine at the County Line, August 24 - Do you know of non-farming family or friends that want to learn more about agriculture and have a great meal at the same time? Encourage them to attend an elegant evening on the farm at the Lowell and Judy Vos farm beginning at 5:30 pm on Thursday, August 24, on the county line of Plymouth and Woodbury Counties. “Dine at the County Line” is a new event hosted by ISU Extension and Outreach in Plymouth County and Siouxland Ag in the Classroom.  The event will encourage communication between local farmers and area residents that no longer have a connection to the farm.  Every table will have a farmer/host for further discussion, along with other activities.  Registration is open, and there is limited seating. The cost is $20 per person or $100/table of six.  See more information about the event on the Plymouth County Extension Facebook page, or register at this web site if you are a non-farmer that would like to attend!
 
THANKS FOR SUBSCRIBING!
Serving Cherokee, Ida, Lyon, Monona, O'Brien, Osceola, Plymouth, Sioux
and Woodbury Counties.
My mailing address is:
Iowa State University Extension & Outreach
251 12th ST SE
Le Mars, IA 51031

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