Cottonwood seeds are/will begin spreading throughout the Midwest.  Cotton woods can be either male or female, however it’s the fluffy white seeds produced by the females during this time that give the tree its name.  In areas where the cottonwood is established the ground can look like it just snowed.  Cottonwoods typically establish around river banks, islands or other places close to water.  The seeds that land close to a river stream can germinate quickly and the trees can establish quickly. Cottonwoods can live to be over 100 years old. 

From a disease diagnosis perspective the deposition of cottonwood seeds can be confused with dollar spot mycelium.  If the “mycelium” is thought to be cottonwood seedling tuft, rub the material between your fingers.  You should be able to feel the seed, and the white tufted material should ball up like wet thread.