Balsam Woolly Adelgid
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Hagle, S.K; S. Tunnock; K.E. Gibson; and C.J. Gilligan. 1987. Field Guide to Diseases and Insect Pests of Idaho and Montana Forests. U.S. Department of Agriculture, Forest Service. State and Private Forestry, Northern Region. Missoula, Montana. Reprint 1990. Publication Number R1-89-54.
Contents |
Hosts
In Northern Region, subalpine fir and grand fir.
Distribution
Thus far has been found only in northern Idaho, but may occur in Montana.
Damage
Nymphs feed on the bark of all parts of the tree injecting a chemical which causes abnormal cell division. This produces annual rings composed of thick cells ("compression wood") in the stem, and stunting of terminal growth with distinct swellings around the buds and branch nodes ("gouting"). All sizes of trees are attacked, but infestations may be concentrated on the stems or in the crowns. Stem-attacked trees may be killed after 2-3 years of heavy feeding.
Identification
The most obvious indicator of the aphids' presence is the white "Wool"-covered females on the bark of stems or branches during summer months (figs. 28, 29). Without the wool, adults are about one-sixteenth of an inch long and dark purple to black in color. Overwintering nymphs are about one thirty-secondth of an inch long, amber colored, flattened, and fringed with whitish wax. "Gouts" (fig. 30) can be on outer branch nodes and terminal buds, and can stop production of new shoots. Dying or dead branches and crowns are other symptoms.
Similar damages
May be mistaken for damage caused by scale insects. "Wool-" covered females and "gouts" are distinctive.
References
- Furniss, R. L., and V. M. Carolin. 1977. Western For. Insects. USDA Forest Serv., Misc. pub. 1339, 654 p., illus
- Mitchell, R. G., G. D. Amman, and W. E. Waters. 1970. Balsam woolly aphid. USDA For. Serv., For. Pest Leaflet 118, 10 p., illus. Adelges piceae (Ratzeburg)
