A study was recently undertaken in Massachusetts, conducted by researchers from the University of Massachusetts at Amherst and the University of New Hampshire to determine the effects winter moth caterpillar populations are having on subsequent growth in oak trees. This recently published study revealed that damage from the winter moth caterpillar is severely affecting the growth of certain species of oaks. Three tree species in communities in eastern Massachusetts were examined; red oak (Quercus rubra), black oak (Quercus velutina) and red maple (Acer rubrum), for potential impacts to growth following wintermoth infestation.
Winter moth caterpillar damage was found to affect the growth of red and black oaks up to 47%, while no detrimental impacts from the same defoliation was found to affect red maples. Using tree ring analysis, this study linked defoliation to reduced radial growth. One year of defoliation is reducing 2 years of radial growth in these species. Annually a tree produces a ring in which summer wood growth can be differentiated from spring growth; in this study spring wood growth appeared stunted due to the previous year’s defoliation by winter moth caterpillars. Multiple, consecutive years of defoliation can lead to stand mortality.
Additional related results from this study indicate that the winter moth caterpillar population is moving south and west at approximately 7 kilometers per year. While long, cold New England winters help suppress populations, new infestations have reported in coastal areas as recently as 2012.
This invasive pest has been defoliating hardwood trees in Massachusetts since the 1990s. It has also been causing massive damage in Connecticut, Rhode Island, New York, New Hampshire and Maine. The full text of this study, published in the journal “Insects”, can be downloaded and viewed at http://www.mdpi.com/2075-4450/5/2/301.