Poplar-Gall Saperda (Saperda inornata)
Ostry, M.E.; Wilson, L.F.; McNabb, H.S.; Moore, L.M. A Guide to Insect, Disease, and Animal Pests of Poplars. United States Department of Agriculture, Forest Service. Agriculture Handbook 677. January 1989. 118 p.
Importance - Larvae bore in the wood of immature Populus and cause globose galls on the stems and branches. Damage is worst to nursery whips and 1- to 3-year-old trees in plantings. Stems and branches occasionally break off or die above the gall; most trees, however, overgrow the gall. Injured trees generally recover height growth within 2 to 3 years.
Look For -
- Egg niches (horseshoe-shaped scars) on stems or branches cut by the adult beetle.
- Gray beetle one-third to one-half inch long on foliage or stem.
- Broken over or dead tops of trees or branches above the gall.
- White larvae or pupae in the woody tissues inside the gall.
- A gall with a hole on the side will be empty.
Biology - In late spring, the female beetle lays eggs in several niches cut in the main stem and branches. Usually one larva develops in each niche and feeds on the woody tissues, boring irregular galleries under the bark. A globose gall forms around the injured area as a result of the boring. In late summer, the larva bores into the center of the gall, enlarges the gallery, and pupates there. The pupa overwinters in the gall.
Monitoring - Inspect whips and young trees for egg niches or adult beetles in early May to late June. After June, search for galls on stems and branches. If the infestation exceeds 15 percent in the nurseries, prepare to treat the following year. Plantations seldom need treatment even if more than 90 percent of trees are attacked.
- Spray nursery stool beds or rooting beds if monitoring suggests control. Use an insecticide recommended for wood-boring insects, and apply when adults begin making egg niches.
- Plant resistant clones on good sites for Populus.
- Prune rooted nursery stock to remove galls at harvest. Eliminate stem cuttings that have galls.
For Additional Information -
Nord, J.C.; Grimble, D.G.; Knight, F.B. 1972. Biology of Saperda inornata [S. concolor] (Coleoptera: Cerambycide) in trembling aspen, Populus tremuloides. Annals of the Entomological Society of America. 65: 127-135.
Wilson, Louis F.; Ostry, Michael E. 1980. How to identify and prevent injury by the poplar-gall Saperda. St. Paul, MN: U.S. Department of Agiculture, Forest Service, North Central Forest Experiment Station. 6 p.