For control of general diseases and fungus on shrubs and trees I recommend using products that contain Neem oil, which can also be used on fruits, flowering plants, ornamentals, and roses to prevent black spot, rust, leaf spot, and powdery mildew. Neem oil also works to prevent and control many harmful insects.
Some diseases, such as chlorosis (yellowing of foliage) and leaf gall (abnormal bumps or growths on leaves which is a defense response to insects or mites), will require remedies other than spraying chemicals. Chlorosis is usually a sign of iron deficiency and leaf gall can simply be cut away and discarded.
In any event, before spraying your plants for a disease, it's always a good idea to consult with your local professional nurseryman or County Extention Agent for a diagnosis, and appropriate methods for treatment. A leaf and/or stem sample will always help for diagnosis.
When spraying your shrub or tree, make sure to wet as much of the foliage as is possible. Treat only diseased plants and those nearby to prevent spreading.
Homemade Recipes for Treating Fungal Diseases
Try these remedies to see how they work for you:
Fungus: Mix two tablespoons of baking soda into a quart of water. Pour into a spray container and spray affected areas. Repeat this process every few days until problem ceases.
Powdery Mildew:Mix equal parts milk and water and spray on infected plants. Three treatments a week apart should control the disease.
Insects and Fungal Diseases: Combine one tablespoon of cooking oil, two tablespoons of baking soda and a few drops of Ivory soap into a quart of water. Pour into a spray container and spray foliage.
Disease Prevention Tips for Ornamental Plants
- Water plants at the base to avoid splashing water on leaves.
- Water or irrigate plants in the morning hours to allow any water that might splash on foliage dry during the day. Water left standing on foliage overnight can cause development of fungus and disease.
- Plant ornamentals in well-drained soils to avoid root rot, leaf spot and other plant diseases caused by wet feet.
- Space plants properly instead of overcrowding. Overcrowding does not allow for good air circulation; one of the best preventive measures for disease and fungus.
- Make sure you select plants that have demonstrated tolerance to disease - especially if you garden in a hot and humid climate.
