Serviceberry (Amelanchier spp.) shrubs or trees display delicate white flowers in early spring and red or yellow leaves in the fall. They grow up to 10 to 25 feet tall and 10 to 15 feet wide in landscapes and are hardy in U.S. Department of Agriculture plant hardiness zones 3 through 8, depending on the variety. Serviceberry plants prefer partial shade and well-drained soil. Insect pests, including pear slugs and Japanese beetles, may devour the leaves before you can enjoy the fall colors. Ask someone else to apply insecticides if you are pregnant or nursing, and keep children and small pets away from insecticides.
Slimy-looking, dark green to orange pear slugs are actually pear sawfly larvae. These bugs feed on the upper leaf surfaces of serviceberry plants but leave the veins intact. After the 1/2-inch-long larvae finish feeding on the leaves in the summer, a serviceberry shrub or tree looks lacy and brown. The damage, however, is usually cosmetic and does not harm the plant. To control pear slugs, spray the entire shrub or tree with a mixture of 1 part insecticidal soap concentrate and 50 parts water, and repeat the application if you see more pear slugs in late summer.
In the summer, shiny, metallic-green Japanese beetles feed on the upper leaves of a serviceberry shrub or tree. The beetles measure 1/3 to 1/2 inch long and have white hair tufts along the sides of their abdomens. Like pear slugs, Japanese beetles turn leaves into skeletons as they feast. If your serviceberry shrub or tree has just a few beetles, you can remove the bugs by hand. Ask someone for help if you cannot reach the branches without a ladder. Beetle traps can make the infestation worse by attracting more Japanese beetles, notes the University of Illinois Extension.
Leaf miners are flies that damage serviceberry leaves in a variety of ways. The small, black and yellow adults create white speckles as they feed on leaf juices in the summer. As the larvae feed, they create winding trails or mines in the leaves that usually do not kill the plant. Heavy infestations, however, can lead to stunted growth and leaf drop. Insecticides are not effective against leaf miners, according to the University of California Statewide Integrated Pest Management Program. Remove and dispose of infested leaves to control this insect.
Other serviceberry pests include tiny aphids and spider mites, which suck the juices from the undersides of leaves. Sooty mold grows in the clear sticky honeydew that aphids secrete as they feed. Heavy aphid infestations cause curled or yellowed leaves. Spider mites, which have eight legs and are not true insects, produce fine webs and give leaves a mottled appearance. Dislodge aphids and spider mites with forceful water from a garden hose, or spray the entire plant with a mixture of 1 part insecticidal soap concentrate and 50 parts water every week for two or three weeks. A daily water mist also helps control spider mites.