A Sticky Situation on Hackberry Trees

If your neighborhood has Chinese hackberry trees, chances are you've noticed a sticky substance on cars, parking lots and sidewalks. The sticky substance is called honeydew, and might be caused by a pest called the hackberry woolly aphid.

Hackberry woolly aphids appear as fuzzy, bluish white masses on leaves and other tree parts and are about 1/10 of an inch or less in diameter. Not all the aphids have wings, but those that do have distinct black borders along the forewing veins and their antennae have alternating dark and light bands. As the aphids suck out plant juices, they excrete the sticky honeydew. Sometimes blackish sooty mold grows on the honeydew and creates a sticky mess on leaves and surfaces beneath infested trees.

Before initiating any management methods, inspect hackberry tree leaves for signs of the aphids and make sure they are the culprits of the sticky honeydew and not another insect that also attacks hackberry trees and excretes honeydew: the citricola scale.

Populations of hackberry woolly aphid are normally highest in the spring and fall with lower numbers and less honeydew production during the summer. To learn more about this pest of hackberry trees and what to do about them, visit UC IPM's Pest Notes: Hackberry Woolly Aphid.

For information about other pests and problems on hackberry trees, visit the UC IPM home and landscape web page.