University of Illinois trials find disease presence boosts fungicide response
University of Illinois (U of I) trials in 2010 found the most profitable use of strobilurin fungicides occurred when application was based on:
* Disease risk, such as hybrids susceptible to disease or hybrids planted in corn-on-corn situations with reduced tillage.
* Scouting that shows disease is present on the third leaf below the ear or higher on at least 50% of plants prior to tasseling.
“The most consistent profitable use of a fungicide occurs when disease is targeted,” says Carl Bradley, U of I Extension plant pathologist.
He reminds farmers that that yield response returns need to exceed fungicide and application costs. If fungicide and application costs hover around $25 per acre, you’d need a 5 bushel per acre yield increase at $5 per bushel corn to break even.
However, corn prices and fungicide prices can vary. Over time, he notes aiming for a 10 bushel per acre yield increase can better ensure profitability. This mainly hinges on disease severity in corn. In 21 U of I test sites from 2008 to 2010, 10 bushels per acre yield spikes occurred about one-third of a time following fungicide applications.
“When disease severity was less than 10%, we saw just an average of .1 bushels per acre yield response,” says Bradley. “In these cases, a 10 bushel per acre yield responses or more occurred just 14% of the time.
Between 10% and 14% disease severity, there was an average 6.8 bushels per acre response,” he adds. “A 10 bushel per acre yield response occurred 17% of the time.
“At 15% or more disease severity, yield increased on average 15.4 bushels per acre,” he adds. “Ten bushel per acre-plus yield increases spikes occurred 75% of the time.”
Sizeable yield increases can occur with little disease present. Fungicide application at a Perry, Illinois, site in 2009 spiked yields 10 bushels per acre when disease severity was well under 5%.