How to Manage Pests

Pests in Gardens and Landscapes

Ash plant bugs—Tropidosteptes spp.

Ash plant bugs are in the plant bug family Miridae. They occur throughout the United States on ash and may occasionally feed on nearby plants if ash becomes heavily infested and defoliated. Depending on the species, adults may be yellow, brown, or black and nymphs may be light brown or green with black spots. Ash plant bugs overwinter as eggs in twig bark. These hatch in February or March and the nymphs feed until they mature in April or May. The adults feed until June or July when they lay eggs. Ash plant bugs have one or two generations a year.


Nymphs and adults suck plant juices from ash leaves, twigs, flowers, and seeds. Ash plant bug damage usually consists of leaf stippling as well as varnishlike specks. Tiny, dark spots of excrement may be visible on foliage. Extreme infestations can defoliate trees.


Damage is rarely severe enough to cause defoliation or warrant control.  If damage cannot be tolerated, an insecticide such as narrow-range oil or soap may be applied to thoroughly cover leaf undersides infested with nymphs in the spring.

Brown adults and green nymphs of the Pacific ash plant bug
Brown adults and green nymphs of the Pacific ash plant bug

Statewide IPM Program, Agriculture and Natural Resources, University of California
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