Horticulture Q & A

Q: I had black and reddish spots on my Photinia shrub last season and the leaves dropped off. What can I do?

A: This is called black spot and very common in Photinia.
Spotting diseases are very common on a wide range of ornamental shrubs, trees, flower and vegetable plants. These diseases are bacterial and fungal and are present in our landscapes at all times waiting for the right time to invade.
If you had problems last year, expect the possibility of seeing the same next year.
First, clean up all dead leaves and twigs and get rid of them.
Using drip or soaker irrigation rather than a sprinkler system will help. These diseases wait for warm, humid, wet times of the year. This is normally in the spring or fall.
Select a fungicide that has your plant on the label. Spraying should have started already, if you haven’t started yet, do so. Repeat at least through mid-June,  as often as the label recommends. This applies to all plants that get spots or other leaf diseases. Trees, shrubs, roses and vegetables are all vulnerable.
Remember, a fungicide does not treat a disease; it protects new growth against disease. So do not wait to start spraying a fungicide if you plants had a leaf disease last year, start before you see the symptoms.
For more information call the OSU Extension Center, 14001 Acme Road in Shawnee, at 273-7683.