Affected plant lose vigor and cease growth. Spray with recommended fungicide as soon as mildew appears. Small, roundish spots with gray or whitish centers. Several spots may run together, killing the entire leaf. Spray with recommended fungicides two or three times during the season.
Many virus diseases affect zinnias.
Remove and destroy infected plants. Spray with insecticides every few weeks to control sucking insects which spread the viruses. For control see sections in this book dealing with nematodes .