Loblolly Pine Susceptibility to Nantucket Pine Tip Moth: Do Tree Genetics Play a Role?

The Nantucket pine tip moth (NPTM) (Rhyacionia frustrana Comstock) is a regeneration pest of young loblolly pines (Pinus taeda L.) that causes tree deformity, shoot dieback, and growth declines. Different silvicultural techniques are used to grow loblolly pine more effectively, including improved genotypes. Some scientists and growers have hypothesized that more expensive full-sibling families (control-pollinated [CP]) seedlings may be more susceptible to NPTM than open-pollinated (OP) families. The study objective was to assess the susceptibility to NPTM of seven loblolly OP and CP families commonly planted in the southeastern United States by observing NPTM infestation rates and pine growth metrics (height, groundline diameter, volume index, and stem form) over two growing seasons. The NPTM infestation rates varied throughout both growing seasons; however, there was no difference in infestation rates among any of the families. Pine growth metrics varied among families at the time of planting; however, growth metrics did not vary after the first and second growing seasons. Results of this study suggest that NPTM management tactics, such as insecticide use, should not be prioritized based on loblolly pine families alone, as the CP families assessed in this study were not more susceptible to NPTM than OP families. Study Implications: In this study, five open-pollinated half-sibling families and two control-pollinated full-sibling families had no differences in Nantucket pine tip moth (NPTM) infestation rates through two growing seasons (2019-2020). High infestation rates (greater than the 3-year 30% NPTM infestation rate economic injury levels) in September and October for both years and each genotype indicated that NPTM control measures may be warranted for young plantations in the Atlantic Lower Coastal Plain. Growth and stem form differences by genotype had not occurred after two growing seasons but may develop as these stands age and merits their future monitoring.