Plants are most susceptible to infection when young. Infection results in the production of the gall. Galls form on any above-ground plant part. Initially, galls are covered with glistening, green-to silvery-white tissue. The interior of the gall becomes a mass of powdery, olive-brown to black spores. Galls on leaves remain small, becoming hard and dry. Galls on the lower stem may result in a barren plant.These plants will be reddish late in the season.The spores produced in galls survive the winter and germinate in the spring to produce another type of spore that is dispersed by wind or splashing rain and that can infect the plant. Smut infection is favored by dry weather.Anything that creates wounds on plant (hail, blowing soil or sand, cultivation, detasseling) can create infection courts where the fungus can gain entry to the plant. Most corn is more or less susceptible, but the percentage of plants affected in a field is usually not great.