Diagnosing Plant Diseases Part I of IV- Leaves
 (Read 250+ times)
By Agnes Farside
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When inspecting a plant that is in poor health, environmental conditions, the type of care the plant is receiving, even surrounding plants can help in determining if, and what type of disease might have inflected the plant. A gardener needs to make every possible observation of every part of the plant to form an accurate diagnosis, and if needed, consult reference books on plant disease, or even seek help from a professional laboratory. The following are some known leaf diseases, host plants, symptoms, and suggested controls. (This is not an exhaustive list.)
Powdery Mildew
Woody and non-woody plants are hosts to Powdery Mildew, a fungal species, and a gardener will recognize this disease by the white, powdery patches on leaves, flowers, buds, and stems. These patches can grow, covering the entire leaf. They become soft, almost like felt and may turn to the color of off-white or light tan. Leaves may drop off early as they become stunted and curled. To help control Powdery Mildew, remove all dead and dying debris, do not crowd plants, and keep them well watered in dry seasons, but keep the water off the foliage. Ensure the area is habitable (light and soil), for the plant. If it is early in the growing season, chemicals may be an option for the gardener.
Sooty Mold
Sooty Mold is a sugary-type fungus that grows on honeydew caused from the excrement of scale and aphids. The hosts can be almost anything, not just plants, due to the accumulation of insects. Sooty Mold can be identified by its dark-brown or black coating on leaves, which prevents sunlight from getting through to the leaves, causing the leaves to die. In order to control Sooty Mold, a gardener needs to control the scale and aphids.
Rusts
The hosts of rust are many including hawthorn, sweet corn, hollyhock, apple, crabapple, and juniper, just to name a few. Some rust needs hosts in order to survive, such as cedar-apple rust, which needs cedar and apple trees. Rust is identified by raised areas, resembling blisters and can be any shade of yellow, orange, orange-red, brown, or black. Leaves will eventually die and plant growth can be stunted. If the rust is discovered in an orchard, it may be best to remove the infected host before the disease spreads to others. Try growing a resistant strain of the plant and when necessary, seek out chemical options.
Scab
Scab can be caused by several fungi, with crabapple and apple being host to one kind, and aspen, birch, cottonwood, hawthorn, maple, pear, poplar, and willow being host to another. A gardener will know Scab by the irregular shaped, tan to olive green lesions on the underside of a leaf. The lesions will grown and turn black causing the upper surface of the leaf to bulge. On fruit, the Scab is almost circular and velvety feeling, and olive green in appearance. As this disease appears during the rainy season, keep plants pruned to allow good airflow around leaves. Remove any infected leaves or fruit and when necessary use a fungicide spray.
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Author Bio Box: Agnes Farside
 http://www.associatedcontent.com/user/110407/agnes_farside.html
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