Fungicides Best Used for Disease Control

July 19, 2007

WOOSTER, Ohio -- Applying fungicides as a plant health benefit, in the absence of disease or under low disease pressures, is not a practice recommended by Ohio State University researchers.

 

Despite some claims that fungicides can boost corn yields, preliminary university research has found no consistent link between fungicide applications and an increase in yields when disease pressures are low.

Over one growing season, researchers with the Ohio Agricultural Research and Development Center tested six hybrids with various levels of resistance to gray leaf spot and northern corn leaf blight at two Ohio locations: Apple Creek and South Charleston. Half of the trials were sprayed with a fungicide and the other half were left untreated. Researchers compared disease levels and yield responses. With disease levels low -- no higher than 12 percent for gray leaf spot and 6 percent for northern corn leaf blight -- researchers found no differences in yield to fungicide applications between treated and untreated hybrids.

"Because of the data, we continue to recommend an Integrated Pest Management (IPM) approach to managing foliar diseases of corn," said Pierce Paul, an OARDC plant pathologist.

IPM is an approach to crop production that specifically controls a pest or disease while minimizing impact on the environment.

Paul, who also holds an OSU Extension appointment, recommends that growers scout their cornfields for foliar diseases, specifically gray leaf spot and northern corn leaf blight, and apply foliar fungicides only if necessary.

Both diseases can impact susceptible hybrids as they enter a stage of pollination and grain fill during wet periods.

"Given the dry conditions, however, little if any disease is present and fungicide applications may not be needed," said Paul. "Surveys from across the state indicate that it is a very low disease year for corn. For example, after gray leaf spot is first observed on the lower leaves of a susceptible hybrid, it takes 14 to 21 days or even longer under dry conditions for it to develop to the extent that it can impact yields," said Paul. "Given the current stage of the corn crop, the crop will already be at maturity, and by then, the disease won't even be an issue."

According to the Ohio Agricultural Statistics Service, nearly half of the corn crop is silking. Over 70 percent of the crop is in fair to excellent condition, despite this season's moderate drought.

Corn is one of Ohio's most valuable field crop commodities, second to soybeans in acreage and economic value. According to the Ohio Department of Agriculture, corn production contributes $836 million to agriculture. Feed grain serves as a main component of corn production, but the crop is also becoming an integral source for ethanol.

 

Author(s): 
Candace Pollock
Source(s): 
Pierce Paul