In the past, fungicide applications on hybrid corn were mostly regarded as uneconomical. The increased corn-following-corn acres and associated increased disease risk, together with the higher price of corn and fungicide marketing, are responsible for changes in corn production practices. As a result, fungicide applications on corn may be more common in 2007. It is anticipated that most of these foliar fungicide applications will occur during corn tasseling stage and will be aerial applications.

The Iowa State University Extension Pest Management and the Environment (PME) program has received numerous questions over the past couple of weeks regarding the use of foliar fungicides on corn. Even though most applications will occur aerially, the PME program would like to remind farmers to communicate with their applicator and/or dealer to ensure that fungicides are NOT applied when conditions favor drift beyond the area intended for application. Favorable conditions for drift include wind speeds of 15 mph or greater, high temperatures, low relative humidity, or when a temperature inversion exists.

Fungicides containing the active ingredients azoxystrobin and trifloxystrobin are toxic to certain apple varieties. The active ingredients pyraclostrobin and trifloxystrobin should not be sprayed on Concord grapes. Therefore, extra care should be taken to avoid drift onto neighboring orchards or vineyards.

The Iowa Department of Agriculture and Land Stewardship (IDALS) can provide locations of apple orchards and vineyards in the state; please see the Grape and Wine Development Commission.

Next week, we will discuss factors that should be considered before applying a fungicide to hybrid corn.

Red dye is used to calibrate aerial applications. (Kristine Schaefer)

Alison Robertson is an assistant professor of plant pathology with research and extension responsibilities in field crop diseases. Daren Mueller is an extension plant pathologist with the Iowa State University Corn and Soybean Initiative and the Pest Management and the Environment Program. Carol Pilcher is the interim director of Iowa State University's Pest Management and the Environment Program and coordinator of the Integrated Pest Management Program. Kristine Schaefer is an extension program specialist with the Pest Management and the Environment Program.

This article originally appeared on page 197 of the IC-498(16) -- June 25, 2007 issue.