Plant Health

Overview

Plant health is a combination measure of the entire plant staygreen, stalk health and foliar disease resistance. Due to higher disease pressures this measure is much more important in the eastern U.S. than in the West.

How we test

To rate staygreen, visual observations of plant tissue color of leaves and stalks are conducted after black layer. Hybrids with better staygreen have cleaner fodder, more intact plants and are easier to harvest.

Foliar disease ratings are taken in late summer and early fall. We conduct observations to determine presence or absence of: Gray Leaf Spot, Northern and Southern Corn Leaf Blight, Stewart's and Rust. Ratings are also made for the plant's resistance, tolerance or susceptibility to these diseases.

Stalk health ratings are taken at 18%-24% moisture and consist of examination for stalk-rot symptoms, both internally and externally. We determine the absence, presence and severity of anthracnose, charcoal rot, diplodia, giberella and fusarium.

Our rating scale

The following iCORN definitions are used in rating our products:

Resistance: The hybrid's ability to restrict the spread of a disease within the plant. Individual lesions are quickly sealed off and do not spread across the leaf surface, thus preventing negative impact on yield. Resistance is not immunity. Immunity is the state wherein the plant cannot contract the disease.
Tolerance: The hybrid's ability to grow and produce acceptable or even good yields in the presence of the disease. Individual lesions are generally smaller and their spread is delayed or slowed. The degree of tolerance varies from high to low. Plants with high tolerance show little to no yield loss. Plants with low tolerance can suffer yield loss. Tolerance, even high tolerance, can be overwhelmed by extreme disease pressure.
Susceptibility: The hybrid easily contracts the disease and lacks an effective defense mechanism. Individual lesions quickly expand and merge together (coalesce) causing significant plant damage or death. The degree of damage is influenced by environmental conditions and level of disease pathogen present.

These ratings are taken in each region where we recommend their use.

Our rating scale ranges from 0 to 9, with 9 being the best score. iCORN doesn't offer hybrids rating 5 or less on plant health. Here's the definition of our ratings.

Dry, straw-colored plant below 24% moisture. Little or no staygreen. Many tops broken. As drydown continues, leaves can develop a black dusty surface (saprophytes). Early harvest is recommended east of U.S. 31 in Indiana. Hybrids with a 6 rating are generally the highest-yielding products that simply require a little extra management.
Mixed green and straw-colored tissue at 24%-28% moisture. A few dead plants, some tops out as drydown continues. Some foliar disease may be visible. 7s are acceptable east to west.
Good green color at moistures of 22%-26%. Below 24% plant health fades. Minimal stalk rot. Excellent foliar health, similar to a 9 rating.
Green and healthy even at moistures in the low 20s. Little to no foliar disease presence. Clean white fodder at harvest.