Insect diversity and abundance within the canopy of a northern red oak (Quercus rubra L.) orchard in eastern Tennessee

The Watauga northern red oak (NRO) (Quercus rubra L.) seed orchard was established in 1987 by the USDA Forest Service in Johnson County, TN. Originally a genetic test of 220 open-pollinated families, these trees now serve as a seed source for oak reforestation efforts.

Acorn production in the seed orchard has been partially limited due to premature abscission of flowers and immature acorns. The cause of this production loss is unknown, although canopy-dwelling insects have been implicated.

To better understand the insect communities existing in the canopy of the seed orchard, a two-year insect diversity study was conducted in 1992 and 1993. The crowns of 20 trees in five genetic families were sampled for insects approximately every two weeks from March to November. Adult insect populations collected on each NRO family were analyzed statistically for significant differences.

In the two years, 26,536 adult insect specimens were collected, representing 15 orders. Within these orders, 143 families and 541 species have been identified (as of 12/1/94). These numbers suggest a diverse, well-established insect community within the seed orchard.

Of the insects collected, the Asiatic oak weevil (Cyrtepistomus castaneus Roelofs) was the most abundant species, composing 25% of all specimens collected. Other important pests found in the seed orchard were acorn weevils in the genus Curculio and Platycotis vittata P., an oak treehopper.

The overall insect communities collected from each NRO genetic family did not differ significantly. But significant differences were found in populations of certain pest species among NRO families. These variations indicate that genetic differences among NRO families do have an effect on pest populations.

Based on these comparisons, and other factors such as acorn production, NRO families suitable for use in reforestation efforts were identified. NRO Family #200, originating in Limestone Co., AL, demonstrated the most potential for use in the regeneration and reforestation of NRO in the southern Appalachians.

This research has uncovered a very diverse insect community in the canopy of an eastern Tennessee NRO seed orchard. Of these insect species, relatively few (ca. 8%) are pests on the trees. These pest populations did differ among the NRO families, suggesting that NRO genetics influence pest densities. Further research is needed to determine how these insect pests affect the trees and how NRO genetics affect the pests.