Stemphylium blight, caused by Stemphylium sp. Small light- green to yellow spots with a distinct red spot in the center form on leaves. Bacterial leaf blight, caused by Xanthomonas gummisudans , is a problem in wet seasons. A sticky slime exudes from rectangular brown spots on leaves. This corm disease, caused by the fungus Stromatinia gladioli , is more common during periods of cool, wet weather.
Leaves produced by infected corms turn yellow prematurely and die.
Small, reddish-brown, sunken lesions develop on the lower portion of infected corms. When an infected corm is cut in half, dark streaks can be seen radiating out from the core to the surface of the corm. Stromatinia corm rot can be controlled by discarding infected corms, planting in well-drained soils, and harvesting corms during dry weather. Treating the soil and corms with Botran or Terraclor prior to planting will be beneficial. Produced by Communication and Educational Technology Services, University of Minnesota Extension Service.