Late Dry Weather is Hurting Corn and Soybean Yields

Chad Lee, Extension Agronomist, University of Kentucky

The USDA NASS lowered their estimates for Kentucky corn yields by 10 bushels per acre and soybean yields by 2 percent in their latest report. The negative numbers reflect calls and comments we are receiving from producers across the state.

In August, most of our corn and soybean fields looked great. The foliage was lush, canopies were closed and the crop looked to be in excellent condition. Now, farmers are getting surprised about low yields in some fields. Just to clarify, these reports do not reflect all fields. There are some really good yields being reported. But, there are some really bad yields as well and these fields were the surprise. I think the biggest contributor to these bad surprises is the weather. Most of Kentucky was wet early and dry late. The wet weather encouraged shallow root systems. The dry weather late penalized crops with shallow roots.

Corn Disease Update

Dr. Carl A. Bradley, UK Extension Plant Pathologist

Figure 1.  Lesions of northern leaf
blight on a corn leaf
(Photo: Carl Bradley, UK).

With the recent rainfall received in the state, conditions have become more favorable for some foliar corn diseases that are now being observed. UK Plant Pathology interns have been scouting corn fields in western Kentucky for the past few weeks, and they have been observing northern leaf blight, gray leaf spot, common rust, and Diplodia leaf streak. As of July 12, southern rust has not yet been identified by UK Plant Pathology personnel in the state. Below are my thoughts about these diseases and the use of foliar fungicides to manage these diseases.

For more information on Corn Disease in KY see the article on Kentucky Pest New

Corn Diseases to Watch for in 2016: Southern Rust and Tar Spot

Dr. Carl A. Bradley, UK Extension Plant Pathologist

Orange pustules of the southern rust pathogen
covering a corn leaf (Photo: Carl Bradley, UK)

Two corn diseases are already making some news this season. Southern rust and tar spot have been detected in southern states and could potentially make their way to Kentucky this season. So, keeping a lookout for these two diseases is a good idea.

For more information on Southern Rust and Tar Spot see the article on Kentucky Pest News .

Corn Replanting - Disease Risks

Replanting and delayed planting of corn puts the crop at higher risks for certain diseases. The following is updated excerpt from AGR-195 Replanting Options for Corn.

Diseases and Replanted Corn
Delayed planting or late replanting, could result in increased outbreaks of several diseases.
The "virus complex": Infections of Maize dwarf mosaic virus and Maize chlorotic dwarf virus, viruses which survive in johnsongrass rhizomes and are spread (vectored) by aphids and leafhoppers, respectively, cause the virus complex. Compared to corn planted on time, late-planted corn is at an earlier stage of crop development during periods of peak vector activity, and earlier growth stage infection usually results in more severe disease symptoms.