Corn Maturing

Corn crops in the Pee Dee are pretty variable this year.  Irrigated corn is looking good and growers are expecting to see high yields.  On the other hand, dryland corn is all over the map.  Some fields managed to catch some pop up showers that gave some much needed relief during the hot, dry spell we had a couple weeks ago.  Other areas had little to no rain for about a four week span.  Fields that were pollinating during the 100+ degree heat are the ones that seemed to suffer the most.  Below is an ear that suffered poor pollination due to the heat compared to an ear that pollinated a little earlier before the heat wave.

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We’re at the R5 dent stage in some older fields now meaning the kernels are decreasing in moisture and increasing in starch content.  You can distinguish this stage by the milk line moving down the kernel.  You still have about 33 days to maturity once this stage begins.

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The milk line is where the yellow meets the white on the kernel. This one is about 1/2 of the way down.

Some Aspergillus is showing up on ears in dryland fields.  This is the fungus that causes aflatoxins that are toxic to livestock.  We tend to see this more often on fields have been under stress.  The fuzzy, gold colored growth on the ear below is the Aspergillus.

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Corn smut is another fungus that can show up in higher incidences following periods of heat stress, though heat stress only indirectly lead to higher levels of corn smut.  When heat and drought interfere with pollination, a number of ovaries (kernels) can go unfertilized.  These unfertilized ovaries are more easily infected by smut than the fertilized.  The best control method is varietal resistance.

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Poorly pollinated ear with several kernels infected with smut.

Lots of stinkbugs are also showing up and causing damage.  During the kernel fill stage, growers may need to treat if 50% or more of the ears are infested with stink bugs.  For a list of labeled insecticides and their rates take a look at the SC Pest Management Handbook, page 69.  The photo below shows stinkbug damage on several individual kernels.

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Northern Corn Leaf Blight is now showing up on a more widespread basis and more growers are applying fungicides.  Fungicides were held off as long as possible to try to make one application last the rest of the season.  Some fields may even go without a fungicide spray if the crop makes it well into the R5 stage with no disease present.  Southern rust still has not been found in SC.  For more disease and fungicide information, refer back to this post.

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