Balsam Fir Chalcid Causes Loss of Fraser Fir Seed

Forest tree seed are often attacked by tiny chalcids which destroy the developing embryo and endosperm. In the western United States up to 60 percent of Douglas-fir, true fir, spruce, and pine seed are consumed by various species of Megastigmus (Keen 1958). In Scotland, Hussey (1955) reported that up to 95 percent of the Douglas-fir seed was destroyed by M. spermotrophus Wachtl. Losses of from 22 to 57 percent of balsam fir seed in Canada were reported by Hedlin (1956) due to M. specularis Walley. Insect-caused losses of seed from Fraser fir, Abies fraseri (Pursh) Poir., have never been evaluated; but, because of increased interest in growing this species for Christmas trees, information about the effect of insects on the limited seed source was needed. During the past few years, we have established that M. specularis attacks Fraser fir seed in the Southern Appalachians and may cause serious losses. Fraser fir cones were collected from Roan Mountain, North Carolina, in September of 1964 and 1965 when the cones were fully mature. After airdrying for about 2 weeks, the seed was extracted and stored in cheesecloth sacks at room temperature for about 1 month. The seed was then transferred to polyethylene bags and refrigerated at 0°F. until removed for examination. Each year, 10 lots of 100 seeds each were dissected under a microscope to determine the degree of insect infestation. To determine the feasibility of a nondestructive method of seed examination, X-rays of seed stored in 1964 and 1965 were taken in April 1966.

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Author(s): Charles F. Speers

Publication: Tree Planters' Notes - Volume 19, Number 2 (1968)

Volume: 19

Number: 2