Effects of Invasive Winter Moth Defoliation on Tree Radial Growth in Eastern Massachusetts, USA

Abstract

Winter moth, Operophtera brumata L. (Lepidoptera: Geometridae), has been defoliating hardwood trees in eastern Massachusetts since the 1990s. Native to Europe, winter moth has also been detected in Rhode Island, Connecticut, eastern Long Island (NY), New Hampshire, and Maine. Individual tree impacts of winter moth defoliation in New England are currently unknown. Using dendroecological techniques, this study related annual radial growth of individual host (Quercus spp. and Acer spp.) trees to detailed defoliation estimates. Winter moth defoliation was associated with up to a 47% reduction in annual radial growth of Quercus trees. Latewood production of Quercus was reduced by up to 67% in the same year as defoliation, while earlywood production was reduced by up to 24% in the year following defoliation. Winter moth defoliation was not a strong predictor of radial growth in Acer species. This study is the first to document impacts of novel invasions of winter moth into New England.

Invasion of Winter Moth in New England: Effects of Defoliation and Site Quality on Tree Mortality

“…The significant radial growth divergence between Quercus and P. strobus RWI from 2005-2010 suggests the presence of a stressor that is specific to Quercus. Radial growth analyses of individual trees throughout this region (including at some of the study sites of the present study) found that winter moth defoliation was a strong predictor of radial growth of Quercus trees defoliated by winter moth, when tested concurrently with site and year as random covariates [21]; however, other factors (e.g., other defoliators, pathogens, physical stressors) were not tested. According to Massachusetts aerial detection survey (ADS) data, winter moth defoliation occurred throughout much of eastern Massachusetts from 2004-2011 [11].…”

“…While site index and winter moth defoliation only explained 20% and 13%, respectively, of the mortality across our sites, the lack of relationship between stand relative density and % Quercus in dead stems suggests that some density-independent factor may have contributed to some of the mortality noted in our stands. Although we cannot be certain that Quercus mortality was attributable to winter moth and not some other defoliator, pathogen, or physical disturbance, the abundance of winter moth in eastern Massachusetts over the last decade, the known relationship between percent winter moth defoliation and radial growth [21], and the dominance of dead Quercus trees in snag classes 1-3 (and thus the assumption of tree mortality occurring within the 1995-2010 period) collectively implicate winter moth as an important contributor to Quercus mortality in these forests.…”

“…In total, 787 (Q. rubra = 227; Q. velutina = 167; P. strobus = 311) trees were cored from the 13 study sites. As per Simmons et al [21], Q. rubra and Q. velutina were combined for radial growth analyses and are herein referred to as Quercus when applied to tree core and mortality results, as these two species are both in the Erythrobalanus subgenus and can hybridize [33]. Although Q. alba L. was present at some of the study sites, this species did not occur in sufficient numbers across all sites to be included in radial growth analyses.…”

“…This threshold was determined using the regression equation for current year winter moth defoliation and Quercus RWI provided in Simmons et al [21], as follows. The defoliation level at which the upper 95% confidence interval of Quercus RWI was equal to the y-intercept value of the regression was calculated using JMP ® Pro 10.0.0 software.…”

Variation in Captures of Adult Winter Moths (Operophtera brumata) in Coastal Maine Over Two Years

“…The typical damage results in partially defoliated leaves, but can cause lasting damage to the tree. Simmons et al (2014) showed that defoliation by winter moth caused significant decline in tree growth in red oak (Quercus rubra L.) in Massachusetts, as measured by growth rings in increment cores of tree stems. Embree (1967) reported that repeated defoliation by winter moth resulted in as much as 40% tree mortality in red oak stands in Nova Scotia.…”