Shrubs are smaller than trees and more noticeable since they are at eye level. According to Yardener, these plants have several woody stems that grow as high as 15 feet tall. Shrubs are mostly used for privacy or windbreaks, in addition to adding color and texture to landscapes. Gardeners need to understand the challenges affecting shrubs so they can keep shrubs healthy.
Bacterial and Fungal Diseases
Erwinia fire blight and Bacterial canker are the two most common bacterial infections attacking shrubs. You'll need fungicides containing copper to manage bacterial diseases, although using them can burn young shoots or cause spotting on leaves.
Common foliar fungal diseases include anthracnose, shoot blights, leaf spots and twig dieback. You can control these diseases by removing infected leaves and using a general fungicide.
Leaf Scorch, Wet Feet and Spine Spot
Leaf scorch, which affects roots, crown and the vascular system, occurs when leaves fail to receive enough water. Other causes include high temperatures, root damage from transplanting, compacted soil or excessive fertilizer and road salt. Protecting plants with windbreaks and keeping soil moist in autumn will help control the problem.
Wet feet is a condition in which plants turn yellow then brown with an entire plant dying quickly. Spine spot involves small grayish brown scratches on both inner and outer leaf surfaces. It occurs in early spring and is caused by leaves being damaged from windy spring conditions. Avoid spine spot by planting shrubs in a sheltered location or by providing erect wind barriers.
Aphids are one of the most common shrub pests. They're small green insects usually found in large groups on the first spring growth. These pests suck sap from stems; wash them off or spray shrubs with an insecticide containing malathion or acephate.
Japanese beetles eat foliage parts and sometimes flowers from shrubs. Pick them off bushes by hand or spray foliage and flowers with an insecticide. Other common pests include scales, leaf miners and lace bugs.
Chemical injuries can occur from not using pesticides properly, so carefully follow label directions. Usually, plants are at greater risk for damage if you apply pesticides on humid, hot days. Applying pesticides to wilted foliage also can cause chemical damage.
Applying excess fertilizer can damage roots and scorch leaves, turning them brown. Newly planted or young shrubs are most vulnerable to over-fertilizing. Injuries can also occur to shrubs close to roads or walkways where excess salt or other de-icing chemicals have been used.