Insects Associated with Southern Magnolia (Magnolia grandiflora L.) in East Tennessee

No comprehensive studies have been conducted to assess the insect fauna associated with southern magnolia, Magnolia grandiflora L. Thus, a two-year study was initiated in 2000 to: 1) determine the richness and abundance of insect species associated with southern magnolia in East Tennessee, 2) compare the insect fauna collected from upper and lower tree canopy levels during 2001, 3) compare the insect fauna collected from pitfall traps and malaise traps at two sites, 4) compare the floral insect visitors of southern magnolia, and 5) develop a species database for future studies.

The insect fauna associated with southern magnolia was evaluated at two sites: 1) a forest site located at the University of Tennessee Forestry Experiment Station and Arboretum in Anderson Co., TN, and 2) an urban site located on the University of Tennessee Agriculture campus in Knox Co., TN. Insects were collected from six mature trees from November 2000 through June 2002 using four collecting methods (pitfall traps, malaise/pan traps in the upper and lower canopy, floral collection, and canopy fogging).

During this study, 5,757 insect specimens, representing 480 species in 119 families and 12 orders, were collected. Potential insect pests and beneficial predators, parasitoids, and pollinators also were identified. Significantly (P < 0.05) greater numbers of insects were collected from the upper canopies of trees than from the lower canopies, possibly due to the more rapid decay of specimens in traps from the upper level, which attracted dipterans in the families Calliphoridae, Muscidae, and Sarcophagidae. The number of species collected in the two canopy levels was similar (n = 243 and 230 species in upper and lower canopies, respectively). Significantly (P < 0.05) more specimens were collected at the urban site, probably due to more favorable environmental conditions including temperature and food resources. Significantly (P < 0.05) greater numbers of species were collected at the forest site, probably due to the greater diversity of plant life and habitat structure. Also, significantly (P < 0.05) more specimens and species were collected on the flowers of southern magnolia in 2002 than in the adjusted data (*0.6667) for 2001, in part due to the addition of floral sticky trap samples and collection times.

This newly developed database containing information on species associated with southern magnolia will be helpful to nursery producers, homeowners, and scientists to better understand the incidence and impact of exotic insects or diseases on plant health. This research may facilitate future studies on insect/plant interactions, alternate pest management strategies, biocontrol of pests, or pollination of flowers of southern magnolia.