disease, followed by a second application 14 days after, if environmental conditions are favorable for disease development (see §Disease cycle). Upon browning of corn sheaths, Quilt is not to be applied. This fungicide can only be applied a maximum 2 applications/yr. Ground and aerial application are both acceptable. Proline 480 SC Proline 480 SC is to be applied at . This fungicide can only be applied a maximum 1 time/year. Only ground application is acceptable. A 24-hour re-entry time is required (minimum amount of time that must pass between the time a fungicide is applied to an area or crop and the time that people can go into that area without protective clothing and equipment). Tilt 250 and Bumper 418 EC Tilt 250 is to be applied at . Bumper 418 EC is to be applied at . Both fungicides are to be applied when rust pustules first appear. If disease is prevalent after primary application, a second application 14 days later may be necessary. Two weeks later, a third application can be made under severe amount of disease. Ground and aerial application are both acceptable. When spraying fungicides Quilt and Headline EC at at tassel stage using a tractor-mounted powered sprayer using , average yield was seen to increase. The use of fungicides can be both economically and environmentally costly and should only be applied on susceptible varieties and large-scale corn production. In order to prevent fungal resistance to fungicides, all fungicides are to be used alternatively, switching fungicides with different modes of action. Pyraclostrobin (Headline EC) and azoxystrobin are Quinone outside Inhibitor (QI) fungicides, whereas propiconazole and prothioconazole are DeMethylation Inhibitors (DMI) fungicides. Weed control By removing weeds, above ground airflow to the crop is increased, relative humidity is decreased, and it limits infection at the most susceptible times. Importance Before 1970, corn grey leaf spot was not prevalent in the United States, however the disease spread during the mid part of the decade throughout low mountain regions of North Carolina, Kentucky, Tennessee, and Virginia. Today, the disease has expanded to Delaware, Illinois, Indiana, Iowa, Maryland, Missouri, Ohio, Pennsylvania and west Tennessee. Corn grey leaf spot can be an extremely devastating disease as potential yield losses range from . At higher disease levels, even greater losses can result. When a corn plant's ability to store and produce carbohydrates (glucose) in the grain is diminished, yield losses take place.