Shrubs can be affected by many different kinds of diseases. Various factors such as overcrowding, poor soil, lack of proper nutrition and drought can all make shrubs more susceptible to problems. Although many diseases are treatable, in some cases it is best to remove the affected plant so that other shrubs are protected. The main factor in treating shrubs is to know what is affecting them, since each type of problem must be handled individually. Preventative measures can also help to reverse or slow the progression of disease.
Inspect the leaves of your shrubs for problems. Powdery spots on the leaves are likely a sign of powdery mildew, which can spread rapidly. Give susceptible plants more room when possible, to prevent the spread of spores. Treat plants with a fungicide such as azoxystrobin as soon as you see any signs of powdery mildew.
Check the overall look of the plant. Plants which appear generally unhealthy, with discolored and dying leaves throughout, may be suffering from root rot. Shrubs can be helped by insuring their soil has good drainage, as roots which are continually wet are more susceptible to root rot. This problem is usually caused by a fungus and can be treated by mixing a fungicide such as Banrot 8G into the soil.
Treat brown spots on the leaves with the fungicide azoxystrobin or chlorothalonil. These spots are usually caused by different types of fungi and will spread if not controlled. Although these diseases may not kill a shrub, they will cause it to fail to thrive, drop leaves prematurely and generally be unattractive.
Kill any pests which infect your shrubs, causing it to be sickly and in some cases even killing it. These can include such pests as aphids, spider mites, borers, beetles, lace bugs and caterpillars. Depending on which pests you have, your shrub’s leaves may be curled, discolored, spotted or drop off the plant. Identify which pests are attacking your shrubs, and use an insecticide which will kill them. Insecticidal soap is a good choice if you want to avoid harsh poisons.
Inspect your shrubs on a regular basis to make sure your treatments are working. Many fungicides and insecticides must be reapplied often. Check the label to determine reapplication intervals and handling procedures.