Pine Tip Moth, Rhyacionia spp., Response to Herbaceous Vegetation Control in an Intensively Site-Prepared Loblolly Pine Plantation

Abstract

Abstract Herbicide release treatments were applied to an operationally regenerated loblolly pine (Pinus taeda L.) plantation to assess the effects of vegetation control on pine tip moth (Rhyacionia spp.) damage. Treatments included banded herbicide applications (1.5-m wide bands centered over rows of seedlings) for 1 or 2 years after planting, broadcast herbicide applications (total area covered) for 1 or 2 years after planting, and an untreated check. All of the herbicide treatments significantly reduced the mount of herbaceous vegetation and improved the survival and growth of planted pines. By the end of the third growing season, pine survival in the check plots (67%) was significantly less than survival in all of the herbicide-treated plots (≥92%). Trees in herbicide-treated plots suffered more tip moth damage than trees in the check plots during the first two growing seasons after planting, but by the third growing season, damage to trees in the check plots was equal to that in the herbidde-treated plots. The method or number of herbicide applications did not have a substantial effect on tip moth infestations. Pine growth gains resulting from reduced vegetative competition were more than enough to compensate for higher tip moth damage following herbicide treatments. However, increased tip moth damage still reduced potential growth gains. Two herbicide applications did not significantly improve pine survival or growth compared to one application, but the broadcast treatments produced slightly larger trees than the banded treatments by the end of the third growing season. For. Sci. 36(4):1105-1118.