Production Blog

Put Your Scouting Boots On

Be very worried if you see this weed in your field this spring. Palmer amaranth is expanding its range and the first line of defense is catching outbreaks early. (DTN photo by Pamela Smith)

DECATUR, Ill. (DTN) -- Reports that black cutworm are at work in cornfields have filled my inbox this week. I know it's showing my soft farm girl side when I say that rowing the first field of corn each spring takes my breath away. On the flip side, nothing makes my stomach turn faster than seeing a path of healthy corn mowed down by this despicable pest. Wait... yesterday's word that armyworms are clipping heads of wheat may be worse -- that crop has almost made it to the finish line.

This year is filled with reasons to get to the field and scout. Economic thresholds have changed dramatically for both corn and soybeans based on today's commodity prices, observes DTN Contributing Agronomist Dan Davidson. Actively scouting for insects, weeds and diseases is the best way to determine if insecticides and fungicides will pay this year.

Palmer amaranth is already showing its hand and growers are being asked to help identify the spread of this hard-to-control weed species. University of Tennessee weed scientist Larry Steckel noted in his university bulletin that a large rain event has now helped activate the pre-applied herbicides in that state. However, the bad news is the long dry spell that preceded it allowed a lot of weed escapes, which may be difficult to control.

The University of Illinois issued a statement this week warning growers that emerged Palmer seedlings had been identified May 7 near Kankakee, Illinois. It's expected that nearly every county in Illinois now has Palmer present and much of that is resistant to glyphosate. Tissue samples from suspected plants are being accepted at Illinois' Plant Clinic and molecular biology screening is available to make positive identifications. http://bulletin.ipm.illinois.edu/…

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Don't forget diseases, advises Davidson. This time of year pythium is an issue, particularly if temperatures are cool. Read more here: http://cropwatch.unl.edu/…

Frogeye leaf spot, Cercospora leaf blight, Phytophthora stem rot and white mold top Davidson's list of diseases in soybeans as the season stretches on. Anthracnose, gray leaf spot, northern corn leaf blight and common rust are worth looking for in corn.

"Also look for nutrient deficiency symptoms as you walk the crop," he added. Don't forget to look for below-ground problems. Root digs are the best way to determine if Bt corn traits are holding up to corn rootworm. Soybean cyst nematode and iron chlorosis can put pressure on soybeans. Soybean roots should be well-nodulated and have nodules that are pinkish or red when split.

"Mid-summer scouting is a good time to monitor the crop too. Let the crop tell you what is happening and make corrections next season," Davidson said. "Don't rely on yield maps at the end of the season to identify problem areas in the field because it will too late to identify many of the causes."

For a general guide on how to scout crops go to:

http://ipm.missouri.edu/…

For more information on how to scout corn go here: http://corn.agronomy.wisc.edu/…

Pamela Smith can be reached at Pamela.smith@dtn.com

(AG)

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