Black Fungus on Maple Leaves

Pest Identification

• Among the sap-sucking pests, aphids are the most likely to cause the growth of sooty mold or black-colored fungus on maple trees. Aphids are oval-shaped, soft-bodied insects that primarily infest foliage undersides. The pests pierce tender plant areas with their specialized, long mouth parts and feed on the sap or plant juice.

Causes of Fungus Growth

• As aphids, or any other sap-feeding pests, feed on maple trees, they produce a sticky liquid called honeydew as a form of excrement. Since the pests are unable to digest all the sap they suck given the high level of nutrients contained in it, they excrete it as honeydew. This shiny, sticky honeydew coats infested plant areas and invites the black-mold-causing fungi to start growing.

Black Mold Fungi

• Black fungus is the result of several fungi. Common fungi in landscape maple trees and other plants are from the Fumago, Scorias, and Capnodium genera. Other less common mold fungi include Aureobasidium, Limacinula, and Antennariella. Though certain fungi are host specific, black fungus generally starts to grow on any plant areas covered by honeydew.

Management

• The best way to manage black fungus on maple is to control the pest infestation. Introduce natural aphid predators in trees as a biological control option. These predators include lacewing, syrphid fly, certain species of parasitic wasps, and lady beetle. Chemical control options include the use of products containing permethrin, acephate, or malathion. Avoid the excessive use of chemicals, since this can harm the natural predators of the pests that are already present in the tree.