Distribution and health of red pine (Pinus resinosa) in response to red pine scale (Matsucoccus matsumurae) in Acadia National Park, Maine

Wheeler, Jesse; Seirup, Camilla; Short, Mary; Miller, Kathryn; Connery, Judith

Executive Summary from document: Red pine scale (Matsucoccus matsumurae) was confirmed on Mount Desert Island (Town of Mount Desert), Hancock County, ME in September, 2014. Red pine scale is an invasive insect from Japan that attacks red pine (Pinus resinosa), which is native to the northeastern US. Red pine is found in patchy stands of varying densities, sizes and age classes throughout lands administered by the National Park Service (NPS) as the Mount Desert Island district of Acadia National Park (ANP) and non-federal lands on Mount Desert Island (MDI). Two areas of symptomatic or dead trees were believed to be the epicenters of the infestation, while stands in other parts of the park show little, if any, symptoms of red pine scale infestations. The goals of this study were to determine the distribution of both red pine and the red pine scale infestation, and establish permanent plots that can be used in the future to quantify the health and changes in red pine stands within ANP over time. We assessed red pine presence and condition from 132 observation points in October, 2014, and established 63 permanent variable-radius plots with over 1000 trees measured. Field work was conducted in the winter when the scale is dormant to prevent spread. We found that the scale is more widely distributed across MDI than originally thought; it is present at least 11 kilometers from the epicenters of the infestation. Red pine stands in the interior of MDI were healthier than those closer to the ocean. Red pine was the most abundant tree species measured within permanent plots (52%) and had an average diameter at breast height of 27.7cm and a density of 654 trees/ha, yet its dominance is declining. Signs and symptoms of red pine scale were seen on all age and size classes of red pine, and some trees that had no visible symptoms were infested. Average red pine health status for combined live and dead trees was 2.7 on a scale of 1 (healthy) to 5 (dead). Most of the red pines (71%) measured were alive, averaging 1.7 on the health status index. Red pine scale was detected on 30 of 52 twig samples analyzed with six twig samples coming from areas with pines that appeared healthy but were infested. Regeneration data collected was incomplete because of deep snow covering most seedlings. However, most plots were regenerating with spruce / fir (24 plots) or white pine (10 plots). Dead red pine trees that appear to have been dead for five or more years showed very low levels of decay, averaging 1.4 on a scale of 1 to 5 with 1 being the least decay. Woodpecker damage was observed on 23% of 125 dead red pines. With a slow rate of decay and few trails and roads through the infested areas, we predict that few trees will become structurally unstable in the next three to five years. We do not recommend removing snags unless they present a hazard to people and property; however, repeat surveys are needed in the next few years to accurately assess the rate of decay and hazard potential of standing dead red pines. A baseline of regeneration in red pine stands has been collected to enable managers to track changes in forest dynamics, although deep snow affected our ability to fully quantify the understory. Long-term monitoring of red pine in Acadia can be used to document the spread of red pine scale across the landscape as well as subsequent changes in forest composition as a result of widespread red pine mortality. Additional work is needed to analyze tree cores that we collected to determine if the date of infestation and red pine health decline are reflected in the cores."