Thinning Southern Bottomland Hardwood Stands: Insect and Disease Considerations

The effects of thinning on insects and diseases have not been thoroughly examined in southern bottomland hardwood forests. To address this issue, a study was initiated at sites in Mississippi and Alabama. These study sites allowed us to make observations concerning insect and disease activity 1-5 years following thinning. On all sites there was an unthinned control and 1 or more thinned areas. Mississippi study sites received only 1 type of thinning treatment, whereas sites in Alabama were subjected to 3 different thinning treatments: (1) light thinning to 70-75% residual stocking, (2) heavy thinning to 50-55% of residual stocking, and (3) B-line thinning to a desirable residual stocking for bottomland hardwoods (Putnam et al. 1960). Study sites in Mississippi were surveyed for insects and diseases before and after thinning operations. Woodboring beetles (Coleoptera: Buprestidae, Cerambycidae, Scolytidae, and Platypodidae) were of primary interest as some species are associated with tree mortality and wood-degrade. Signs and symptoms of pathogens associated with rot andlor decay were tabulated. Potential effects of insects and diseases should be of interest and concern to resource managers. We report here on the numbers of insects and diseases recorded during individual tree surveys, as well as on the results of insect sampling conducted in thinned and unthinned stands. Observations on tree wounding, as a result of thinning, are reported. Conclusions and hypotheses will be drawn and stated as to the management and ecological significance of these findings. Directions for future investigations also will be recommended.