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Tuesday, Jan. 24, 2017

Crops growing well despite soggy start

Posted Monday, August 2, 2010, at 5:36 PM

With the delayed planting, replanting and weather conditions, corn is in various stages of growth Some fields that I have checked are in the R5 (dent stage) and there are some indications of black layer development.

Weather conditions are favorable for disease development and fungicide applications lasts from 14 to 21 days. All of this means that we still should check fields for any signs of significant disease development, especially in later developing fields. In checking your fields, you may find a disease imposter. The corn leaves do look like they are diseased but actually they are not. It is called "disease lesion mimic" because it looks like typical corn disease damage, but so far plant pathologists have not been able to isolate a pathogen that causes it.

Typically it starts with yellow spots on the lower leaves that develop into necrotic dead tissue. Sometimes it is just spots in the field, sometimes it affects the entire field. Along with the leaf damage, stunted plants and some plants without ears have been found. Research from Purdue University indicates that environmental factors that seem to trigger disease lesion mimic are bright light, like on a cloudless day after a rain; low humidity; and low nighttime temperatures. There is no treatment for it. Since there is no pathogen, the problem is probably genetic. The trait has been found in hybrids from different sources.

We have received a few reports of webworms in soybeans. Webworms are green to yellowish green and have three dark spots on the side of each segment. Some species may have stripes down the length of the body. They reach about 1 inch long at maturity.

Look for rolled, skeletonized, and webbed leaves as webworms remove leaf area and visible frass as worms feed. Small soybeans either late planted or double crop are most at risk. Treat soybeans when 20-30% of leaf area is showing damage. Use lower end of threshold as soybeans enter reproductive stages.

Wheat yields and other information are available from the University of Missouri variety testing program. It was not a good year for wheat. The plots that survived did well. Top yield of 76.3 bushels per acre was measured at Portageville, Mo. Across the state, at Trenton, Mo., in Grundy County, near Iowa, the top yield was 55.2 bushels. In northeast Missouri the top variety made 40.4 bushels. At Columbia the top average was 55.9 bushels, in spite of drowned plots and a late replant. All plots in western Missouri faced problems both in planting and at harvest. Wet weather delayed or drowned out plots last fall.

Yield results are available at your local extension office or at: http://www.plantsci.missouri.edu/variety...

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As our local University of Missouri Agronomy Extension Specialist, Crook has been writing a column for the print edition Agriculture page for the past three years and we will now be sharing it on our web version. Crook has a bachelor and masters degree in agronomy from University of Missouri and received his doctorate in Agronomy from Kansas State University. He was in soybean variety development research for 22 years for various seed companies and has been Saline County's agronomy specialist for 10 years.
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