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Late Season Corn Management

Jul 16, 2021

By Jeff Blauwet, CFE Technical Agronomist

We are into that late season last chance to add management part of the crop year. We have corn in the pollination – early grain fill phase which is the most critical part of the year in yield determination. Now is decision time for fungicides, foliar insecticides and foliar feed micronutrients.

Fungicides have become commonly used products and will be more common now that we have decent commodity prices and have some moisture to soften the drought issues, at least for now. The corn crop in general looks quite good considering what we had for June weather. Properly placed fungicides have shown us 10-30 bu + yield responses in farm fields the last number of years. Several factors lead to the “properly placed” part.  Understanding your hybrid’s response potential is a big one to look at. Winfield’s Answer Plot system tests most of the major germplasm to compare the genetics and how they response with fungicide applied. Testing in 2020 plots showed the least responsive hybrid only gained 3.9 bu while the most responsive shown a 35.3 bu gain. Knowing that is important before deciding. Another component is crop rotation. We feel that corn on corn is nearly a no-brainer due to the increased disease pressure that usually comes with the additional corn residue. Lastly, all fungicides are NOT created equal. Like most things in life, you get what you pay for. There is some cheap single mode of action (MOA) older fungicides available but much like herbicides, we can (maybe already have) generate resistance in our diseases to a class of fungicides. We have already done that in beans with Frogeye Leaf Spot. I would recommend we prioritize usage of multiple MOA products like Miravis Neo or Delaro Complete so we can maintain their effectiveness into the future.

Insecticides are also of interest right now, especially in corn-on-corn rotations. We have started to see Western Corn Rootworm beetle emergence being heavy due to ideal hatch soil conditions for them. I expect silk clipping may need to be watched closely in corn-on-corn fields.  Spider Mites are present in most fields and are slowly expanding. They flourish in hot dry conditions like we had in June, so they have a foothold already. Fungal pathogens keep the mite populations in check in “normal” or wet years but if we get back to hot and dry, they WILL be a problem like 2012 was with them. We have seen some grasshopper nymphs along edges of fields and like the mites they flourish in hot dry conditions. I haven’t spotted corn leaf aphids yet, but they often will show up after pollination. They likely are coming yet. Some products like Lorsban have better knockdown and less residual while others have better residual but take a little longer to kill the bugs.

Corn has very high demands on it right now with pollination and early grain-fill happening. It can get a boost from boron or manganese during this stage of growth, and these generally aren’t very costly to add in if the plane is in the air.  This could be even more important in 2021 as root development went more vertical this year due to the drought thus is has less root mass near the top 6” where the nutrients are more likely present.

Talk to your CFE agronomist to help put all the pieces together and make a plan for success.


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