Flowering almonds (Prunus triloba, Prunus glandulosa), sometimes called flowering plums, are ornamental shrubs that make attractive accent plants in smaller yards. The shrub's fragrant pink or white flowers bloom in mid-spring and give way to red fruit in late summer or autumn. The attractive green leaves turn showy copper and yellow shades in the fall. These Chinese natives thrive in U.S. Department of Agriculture plant hardiness zones 3 or 4 through 6 or 8. Although flowering almonds have the reputation of being hardy and easy to grow, these shrubs still suffer from the occasional disease and pest problems.
Flowering almonds may contract various plant diseases, but the highly contagious fire blight is the shrub's most significant health problem. The bacterial pathogens (Erwinia amylovora) enter the plant through flowers and bark wounds. Once inside, the infection spreads quickly throughout the plant, causing the leaves and blossoms to suddenly discolor and wilt. Blighted twigs develop water-soaked, sunken cankers at their bases and often look as if they've been scorched with fire. Severe blight infections can kill flowering almond shrubs.
Once a fire blight infection has hit your flowering almond, you can control the disease only by pruning out the infected plant tissue. Cut at least 6 inches below infections to make sure you prune into healthy wood tissue. Sanitize your pruning shears or loppers between cuts by dipping the tools into a 10 percent chlorine bleach solution for about 10 seconds. Using a copper-based fungicide often works effectively as a preventative treatment. The University of Georgia College of Agricultural & Environmental Sciences suggests spraying your shrub when it first starts blooming and repeating applications every seven days until bloom time ends. Following the instructions on the products label, mix 1/2 to 2 ounces of liquid product for each gallon of water. Thoroughly spray all parts of the flowering almond shrub for optimal blight control.
Several spider mite species (Tetranychus spp.) occasionally become troublesome on flowering almond plants. The adult females overwinter in the bark and emerge to lay eggs on newly developing foliage when warm weather arrives. Spider mites feed by piercing the leaves and sucking out the contents. Feeding activity might cause stippling or yellowing of the foliage. These tiny pests are very hard to see with the naked eye, but you can often spot the fine webbing they spin on the foliage.
Aphids are tiny, soft-bodied pests that suck the juices out of plant tissue. Aphids tend to group together in large numbers to feed beneath the leaves or on the stems. Feeding activity can cause stunted plant growth, loss of vigor and discolored, distorted or curled foliage. Heavy aphid populations also excrete honeydew, a sticky substance that provides the ideal growing environment for sooty mold fungi.
Spider mites thrive in hot, dusty environments, so reduce dust levels by watering down any dirt pathways, driveways or roadways near your shrub. Hosing down your flowering almond with heavy sprays of water from a garden hose can reduce spider mite and aphid populations by washing the pests off the leaves. Prune out and destroy any foliage that has small, localized pest populations. Horticultural oil sprays can help treat both spider mite and aphid problems. Following the label's directions, mix about 5 tablespoons of oil-based insecticide product into 1 gallon of water. Wait at least 30 days before the next application, if needed.