Spots on a Serviceberry Bush

Entomosporium Leaf Spot

• Entomorium leaf spot, caused by a fungus in the genus of the same name, appears on the serviceberry as tiny, reddish leaf spots that darken and enlarge as infected leaves mature. Spots are sometimes surrounded by a yellow halo and tend to appear on older growth. Dark fruiting bodies and white spores may appear in spot centers. Plants that are severely infected may experience significant premature leaf drop. To address Entomosporium, remove and dispose of infected leaves on the plant, as well as fallen leaves and other debris on the ground around the serviceberry, avoid overhead watering and prune off lower branches and thin out areas of dense growth to lower humidity around the foliage.

Rust

• Multiple species of rust potentially plague serviceberry, causing yellow to orange leaf spots that may enlarge or develop a dark border. Fruit, twigs and stems may become swollen or distorted and bright orange spore masses eventually develop on infected tissue. To minimize rust problems and improve the serviceberry's appearance, avoid overhead watering and prune off infested portions of the serviceberry as soon as you notice an infection. Rusts are complex and require another host besides serviceberry to complete their life cycle, so it is very difficult to achieve complete control of these fungi.

Powdery Mildew

• Powdery mildew is a fungal disease that appears on serviceberry leaves as whitish, powdery spots or blotches on leaves. Infected leaves may become curled, folded or distorted. If flowers are affected, they also suffer distortion and are covered in powdery white growth. This disease is most problematic when humidity is high and the plant is shaded, so to prevent or address powdery mildew, cut back or prune off branches on the serviceberry and adjacent vegetation selectively to improve air circulation and increase the amount of sunlight hitting the leaves. Also avoid excessive or fast-release nitrogen fertilizer applications, as these materials stimulate a flush of tender new growth particularly susceptible to powdery mildew.

Pests

• A few different pests of serviceberry appear as or cause spots on serviceberry leaves or other parts of the plant. Oystershell scales appear on bark as small, brownish and immobile bumps where they feed and potentially cause dieback. These scales are best addressed by pruning out heavily infested portions of the plant and permitting natural scale enemies to flourish by avoiding broad-spectrum, persistent pesticides and alleviating dusty conditions. Lacebug feeding causes whitish-yellow flecks on the upper surfaces of leaves. Feeding by spider mites, which look like tiny, moving dots to the naked eye, appears first as a stippling of leaves followed by leaf yellowing or bronzing and premature drop and is often accompanied by tell-tale webbing. Both lacebugs and mites are fairly easy to address by occasionally spraying the plant down with a forceful stream of water that will dislodge the pests and wash dust off of leaves.