Agronomy Talk

Agronomy Update

E. Indiana and Ohio: Fungicide, Planting Depth, and Unhealthy Emergence

Published on Wednesday, May 7, 2014

Protecting the Flag “Leaf”
In the next few weeks we will be approaching the time for fungicide applications on wheat. Applying fungicides at or immediately after flag leaf appearance provides the best protection against foliar diseases. The flag leaf provides about 50% of the energy to fill the grain head, so it is important to keep it clean. If you want to control Fusarium Head Blight (head scab), then it is best to wait until mid-flowering and use the fungicide Proline® or Prosaro®. Do not apply the strobilurin class of fungicides at flowering as this can increase DON levels, plus it will not control head scab. 



                                                   Click on the chart to download. 

Do I Adjust Planting Depth?
Some farmers are thinking about shallowing up their planting depth to get the corn out of the ground quicker since it is getting a little later. Is this a good idea? The answer is no. Some of the corn may emerge quicker (usually by less than a day), but the long term effects of shallow planting will linger for the remainder of the growing season. You will get less of a stand, more uneven emergence, possibly rootless corn, shorter plants, less drought tolerance, greater chance for herbicide injury, and ultimately less yield. Try a strip to test. Plant a strip shallow and plant the rest of the field deeper. You will be happy with your choice to plant deeper at the end of the growing season!

On the flip side, many areas in Ohio and Indiana are drier than normal and growers are planting deeper to reach moisture. This practice is ok. It is better to plant too deep than too shallow. Planting into moisture will allow for more uniform emergence. How deep is too deep? You should be able to go at least 3” without running into much trouble. Many farmers worry about crusting, but crusting occurs at the surface and affects shallow planted corn as well as deep planted corn.

My Corn Has Emerged But is Yellow in Color
More than likely the corn planted so far is going to be colorful. Unfortunately, the color it is turning is not the healthy dark green we were expecting. It is turning yellow, pale green, and probably will turn purple. Why? Corn is a warm season crop. The optimum temperature for corn is 85-90º F. We are planting at temperatures between 50-60º F (see chart below). Root growth is about 5 times faster at 85º F versus 60º F. So root growth is slow and microbial activity of the soil (which releases phosphorus, sulfur and other nutrients) is slow due to cold temperatures. These two reasons alone explain the odd colors. 



                              Soil temperatures across the midwest from May 4-11, 2014

The plants may stay an ugly color until temperatures warm up or the nodal root system gets established at around the V2-V3 stage. If the plants are uniform coming up, that is the most important thing, not the color. The color will change. Yield should not be impacted from pale yellow or purple corn early.

2,4-D is an effective burndown treatment for many weeds that are glyphosate resistant in Ohio and Indiana including marestail and giant ragweed. Because of its cost and effectiveness it is used on many fields. To avoid crop injury, however, there are some precautions with using 2,4-D. As always, follow the label directions. 

--The amine formulation of 2,4-D is more water soluble and has a greater potential to leach into the seed zone than the ester formulation and should be avoided as a burndown.

--Wait at least 7 days after application before planting at rates <0.5 lb. ai/A. If you use higher rates, you may need to wait up to 30 days. Again, different products have different restrictions, so follow what the label says.

--Tilling the soil after application can increase the risk of injury by moving it down into the seed zone.
Injury chances increase when applied to sandy soils.

--Cool and wet conditions (which most areas have had) increases the risk of injury. It is usually the rainfall received within the first two weeks after application that determines the extent of injury.

--Injury can be avoided or reduced with deeper planting. In fact, the University of Nebraska suggests we should plant soybeans 1.75” deep (in all tillage situations).

Several management practices you can do to reduce the chances for injury not only for 2,4-D, but many of the other preplant herbicides, is to give it at least 7 days prior to planting, don’t plant right before a rain, and plant deeper.


Integrated Pest Management, University of Missouri 2009.

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Mark Apelt

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