To the naked eye, corn and soybeans that were planted later than usual might appear to have made up for the time lost earlier in the spring. The pace at which these plants have grown, though, means they might be prone to a unique combination of challenges. One of these is the increased likelihood of disease.

It’s common knowledge that late-planted corn is more likely to display fungal disease symptoms. Not as well-known is why the corn is so much more susceptible to disease. Bayer CropScience identified the following reasons the crop is more susceptible:

  1. When planting is late, warmer environmental conditions lead to faster disease growth.
  2. Faster fungal growth leads to more inoculum, increasing the odds of infections.
  3. Late-planted corn means plants are younger when the fungi are more active.
  4. Young plants are more vulnerable to infection than older, hardened plants.
  5. Warmer conditions lead to rapid tissue growth on the plants.
  6. Rapid tissue expansion leads to a thinner, waxy cuticle. This compromises the plant's first line of defense against infections.

Bayer CropScience agronomists replicated field trials to test yield response to fungicides applied in corn and ran models using the average yield response and average industry costs for product and application to see if applying fungicides in corn pays.

In short, the agronomists found that fungicides are profitable even when corn prices are lower than where they were a year ago. Three years of trial data show at-tassel applications of StrategoYLD fungicide resulted in an average corn yield increase of 11.bushels per acre. At $5 corn, that translates into a profit of $42.91 per acre.

Soybeans and fungicide

Like corn, late-planted soybeans can grow rapidly when conditions stabilize. This compromises the plants’ natural defenses.  

Late-season diseases aren’t usually a concern in soybeans because they tend to occur when plants are mature. Yet, late planting can affect timing of maturity. Later-maturing plants are more susceptible to
late-season disease.

Of course, the bottom line comes down to a number of factors related to the growing season such as what kind of rain and temperatures will finish out the summer. What is known is that application of a fungicide in soybeans can be as profitable as it is in corn.

For the past several years, soybeans treated with an application of Stratego YLD at flowering averaged 3.25 bushels per acre more than untreated soybeans. This means an additional income of $22.91 for $12 soybeans.