Yield potential still tops hybrid selection list
The specter of Asian rust initially spotlighted fungicide use on soybeans. Now that spotlight is expanding to corn, mirroring a likely increase in corn-on-corn acres in 2007.
The prolific residue that accompanies continuous corn creates a haven for foliar diseases, such as gray leaf spot (GLS), to thrive. Still, remember that fungicides are just one tool for controlling foliar diseases.
"We don't see an advantage to blanketing fungicides across every acre," says Jeremy Groeteke, a research agronomist for Golden Harvest, Waterloo, Nebraska.
Nor is it a given that a hybrid highly resistant or tolerant to foliar disease is your best hybrid pick for corn either grown in rotation or continuously. Disease isn't a problem every year.
"Disease is dictated by Mother Nature," says Groeteke, who spoke along with other Golden Harvest agronomists at a recent Golden Harvest meeting in Council Bluffs, Iowa. In wet and humid years, foliar diseases can thrive. In dry years, they don't.
That's why yield potential still needs to be your top hybrid selection factor.
"Don't necessarily assume that just because hybrids have a great disease score or disease tolerance that they will be the highest yielding hybrid for corn-on-corn," says Groeteke.
Realizing yield potential is a challenge hybrids face year in, year out. That's not the case with disease tolerance or resistance. Some growing seasons have disease-conducive weather where disease resistance or tolerance help hybrids realize yield potential. Others don't.
One constant remains through both kinds of years: Hybrids with mediocre yield potential will yield that way every year.
What to do? In residue-laden fields, pick hybrids with high yield potential and high disease tolerance.
Fungicides are another disease-management tool. In 2006, Golden Harvest researchers evaluated six fungicide treatments on two sets of five hybridsâ€”one set susceptible to GLS and another tolerant to itâ€”at three sites in Iowa, Nebraska, and Illinois.
Researchers tested hybrid sets in continuous corn under no-till or minimum tillageâ€”an environment conducive for disease. Hybrid sets were compared against an untreated fungicide check to assess the impact fungicides had upon hybrid sets.
Results varied. "Depending on the location, there were different responses by fungicides," says Scott Payne, a Golden Harvest Research agronomist stationed in Ames, Iowa. "Not every hybrid responded to a fungicide in the same way. There might have been one hybrid that gained five bushels per acre with a fungicide application, while another hybrid gained 10 bushels per acre."
In other cases, fungicides gave no yield advantage, even with GLS present.
Meanwhile, an average of all study sites and hybrids showed GLS-susceptible hybrids yielded more than the GLS-tolerant hybrids. This led researchers to wonder if differences were due to fungicide applications or to genetic yield potential.
Results of the untreated check showed GLS-susceptible hybrids still outyielded GLS-tolerant hybrids.