Tar spot is a foliar corn disease that has recently emerged as an economic concern for corn growers. Recent data shows corn growers losing 20-60 bu/A in locations with severe tar spot.1 Symptoms include black oval or circular lesions developing on the corn leaf, hence the name “tar spot.”
Environmental factors that favor disease development include cool temperatures, high humidity, frequent cloudy days and 7+ hours of dew at night. Tar spot symptoms appear 14-21 days after infection, and spore production can continue if conditions stay favorable.
After the growing season, the infected tissue dries and is returned to the field at harvest. The fungus then overwinters in infected corn residue and has been proven to survive for more than one year. Unfortunately, managing corn residue doesn’t eliminate the risk of tar spot. Spores can still come from neighboring fields or from fields counties away. When favorable conditions return during the next corn growing season, new spores are released, starting the tar spot cycle over again.
You can limit yield loss from tar spot and other corn diseases by choosing disease-resistant corn varieties, scouting fields frequently throughout the growing season and applying a fungicide when environmental conditions favor disease development. Choose a fastacting fungicide such as Aproach® Prima fungicide to protect your yield from tar spot.
