Urban Forestry

The City of Livingston, along with most of California's Central Valley, has been infested with an imported "Asian woolly hackberry aphid." These insects are primarily host-specific, meaning they target our hackberry trees.

Identification: These pests appear as small white fuzzy tufts less than 1/10 of an inch long. They suck the plant juices from the leaves and excrete a sticky fluid ("honeydew") that covers sidewalks, cars, and anything below the tree. The honeydew is basically sugar; it is unsightly and annoying but poses no health risk. The City Manager and the Public Works Director have initiated control methods to manage this long-standing problem, and a major step in control is knowledge for everyone involved.

Management: The City has treated many infected trees with an integrated pest management (IPM) system. One method injects an insecticide into the ground around a severely infected tree; it is taken up by the roots and carried through the tree to the leaves where the target pest is. The second method is a foliar spray of horticultural oil onto the leaves. Both practices are safe to people and the environment.

Control: Another useful practice is for a resident to use a garden hose with a stream of water to spray the insects off the leaves reachable from the ground. This helps reduce the aphid numbers and also washes the honeydew from the leaves, reducing the amount of ants using it as a food source.