These insects (family Membracidae) suck and feed on various hosts. At least 40 treehopper species occur in California.
Treehopper adults are commonly brown to greenish but some species have colorful markings. Adults are 1/2 inch long or shorter. They have an expanded first segment behind the head (pronotum) that forms a hoodlike covering over the front, top one-half of their body and may include a thornlike projection. This enlarged prothorax distinguishes treehoppers from most other true bugs (Heteroptera) they resemble. To help you discriminate between types (families) of insects with similar-looking adults see Distinguishing Among Sucking Insects That Resemble Each Other.
Treehopper adults and nymphs also have rows of spines along the length of the hind tibia (longest leg segment), as do also cicadas and leafhoppers. Nymphs have numerous spines on the back of the abdomen. Both immatures and adults readily jump when disturbed, such as when they observe movement nearby.
Buffalo treehopper. Stictocephala bisonia adults and nymphs are brown or green with a yellowish underside. Adults and last instars are about 2/5 inch long. Nymphs have prominent spines on the back, which is characteristic of treehopper nymphs. Host plants include ash, elm, fruit trees, hawthorn, locust, poplar, and many herbaceous plants (e.g., tomatoes and peppers).
Oak treehopper. Platycotis vittata is common in the spring on the lower branches of deciduous and live oaks and occasionally on birch, chestnut, and certain other broadleaf trees. Individuals commonly aggregate in rows on twigs. Adults are bronze to olive-green with reddish bands. The surface of their pronotum is covered with tiny pits. The nymphs are black with red and yellow markings and have two soft, black spines on the back. The spring generation of nymphs is especially colorful.
Threecornered alfalfa hopper. Spissistilus festinus adults are about 1/5 inch long and green without distinct spines on the back. Nymphs are greenish with 12 pairs of hairy spines on the back and a protruding tail-like process at the rear of the abdomen. Hosts of adults and nymphs include various legumes, herbaceous weeds, and certain low-growing plants grown as cover crops. Threecornered alfalfa hopper feeding in grapes vectors Grapevine red blotch associated virus.
Treehoppers develop through three life stages: egg, nymph, and adult. After hatching from an egg, nymphs develop through several (commonly five) increasing larger instars. Late instars develop wing pads and the last instar sheds its skin to emerge as an adult. Treehoppers have one to several generations per year, varying by location and species.
Treehopper feeding damage in landscapes is generally slight and not threatening to plant health. They excrete sticky honeydew on which blackish sooty mold grows. This fouls leaves and twigs and surfaces underneath infested plants.
Most treehoppers injure plants primarily by making numerous, small slits or punctures in bark where females lay eggs. Egg punctures cause bark to appear roughened and oviposition-injured twigs may die back. Where terminal dieback occurs regrowth can be crooked or distorted. On herbaceous hosts, treehopper feeding and egg laying sometimes girdles and kills green stems. Mature woody plants tolerate extensive egg laying damage, but the growth of heavily infested younger plants may be slowed.
For species known to feed on many different plants (e.g., buffalo treehopper and threecornered alfalfa hopper), removing some of the alternate hosts (e.g., herbaceous weeds) may reduce treehopper feeding on more-valued plants. A forceful stream of water can provide some control on small plants.
If treehoppers were abundant on deciduous trees, shrubs, or vines the previous season and damage cannot be tolerated, horticultural (narrow-range) oil can be applied to thoroughly cover terminals during the dormant season to kill overwintering eggs. During the growing season, high populations of nymphs and adults may be reduced by spraying exposed insects with horticultural or narrow-range oil, insecticidal soap (potassium salts of fatty acids), or another insecticide.
For photographs and references for more information on numerous species, see Treehoppers Aetalionidae, Melizoderidae, and Membracidae (Hemiptera). For more photos of planthoppers and other insects they can resemble see CalPhotos and near the bottom of Hemiptera (Bugs) from Orange County, California.
Adapted from the publications above and Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide, University of California Statewide Integrated Pest Management Program (UC IPM).
Adult oak treehopper.
Adult threecornered alfalfa hopper and stem girdled by its feeding.
Nymph of threecornered alfalfa hopper with spines characteristic of immature treehoppers.
Adult oak treehoppers and egg laying wounds that caused roughened bark.
First instar (nymphs) of oak treehopper.