Does Planting Time Affect the Onset of Powdery Mildew in Zinnia Crops?

This past growing season I examined powdery mildew presence for three successions of zinnia crops. The successions included three different varieties of zinnias to determine if there were variations in powdery mildew presence for the different varieties. Benary Salmon, Ballerina, and Oklahoma White were the varieties I chose to sample. Each succession was started 3 weeks apart.