Figure 1 . Damage Aphids feed on plants by sucking plant sap from the leaves, twigs or stems. When abundant, aphids remove large quantities of sap, reducing plant growth and vigor. Aphids feeding on developing leaves also can produce leaf curl injuries. This is most frequently observed on birch, mayday, lilacs, honeysuckle, crabapple and roses.
Most aphids excrete large quantities of a sweet, sticky substance called honeydew.
At times, excessive honeydew dropping from trees can be an extreme nuisance. Also, sooty mold fungus may grow on the honeydew, producing a black, unattractive covering of the leaves. Sooty mold is not damaging to the trees except when it covers leaves and temporarily reduces photosynthesis. Detection and Monitoring Aphids respond to the increasing temperatures in Alaska summers by reproducing quickly. Often the first sign of aphids will be winged aphids flying about or resting on tree trunks and sides of houses or other structures.