Downy Mildew Seedlings and cuttings are stunted and leaves curl downward. Gray to white fungus lightly covers the underside of leaves. Upper side of infected leaves have yellowed areas. The fungus causes a systemic infection of all leaves of seedlings. Older plants yellow, may be stunted, and die from the top down.
Plants fail to flower.
Peronospora antirrhini Heat and vent to maintain low humidity, especially when weather is cool and cloudy. Water in a manner that keeps leaf surfaces dry. Spray azoxystrobin to cover all leaf surfaces. Before replanting greenhouse beds, steam the soil because the fungus survives in debris. Phyllosticta Blight or Leafspot Yellow spots on leaves collapse and become black.