Leaf crowding

C ause Powdery mildew. The powdery leaf patches of this common plant disease consist of fungal strands and spores. The fungus feeds on plant nutrients, causing leaf yellowing. The problem is most common on upper leaf surfaces. Fungus from 1 plant can spread through a crowded area within days. 

Fortunately, the same controls are effective against many leaf spot diseases. Remove and discard infected leaves. Thin plants and avoid crowding future plantings. Wash your tools and hands after handling infected plants.. Avoid overhead watering. Inspect bedding plants on purchase. Clean up plant debris to remove overwinterins sites. 

Leaves with water-soaked spots rhizomes rotted and soft. Cause Bacterial soft rot. Soft rot attacks during wet seasons in poorly drained soil, entering through wounds in the rhizome made by premature leaf removal or cultivation or carried on the bodies of iris borers. Crowded plants in shady locations are more susceptible to this disease. Infected rhizomes are dry on the outside, but wet, smelly, and slimy inside. This rot may start in the leaves... 

To control all 3 of these diseases, also use cultivation methods that help prevent fungal infections. Maintain good air circulation by selecting a sunny, well-drained site. Each fall, remove diseased or crowded canes at ground level. Prune when plants are dry and rain is not expected for the next 3 days. For persistent fungal infection, apply lime-sulfur spray just as leaf buds break in the spring. 

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