The southern pine beetle (Dendroctonus frontalis) is an insect that develops within pine trees and is native to the forests of the eastern United States. The adult beetle is black, and smaller than a grain of rice. As its common name indicates, the southern pine beetle had been endemic to the southern states. However, as climate change has warmed winters, the southern pine beetle made its way northward. By 2015, the southern pine beetle had been observed on Martha’s Vineyard and on Nantucket.
The southern pine beetle communicates with pheromones. Once adult beetles have found a suitable tree, they bore holes into the tree, and tunnel beneath the bark. These beetles emit scents that call other beetles to the same tree. Once enough beetles have reached the tree, they emit a different pheromone, one that tells other beetles that the tree is full, and that another tree must be found. Female beetles lay eggs beneath the bark. These eggs hatch, and the larvae wriggle about in sinuous tunnels, eating a symbiotic fungus all the while. The tunnels created by thousands of beetles and beetle larvae girdle the tree, killing it in about six weeks. The reproduction of beetles is affected by temperature. The warmer the weather, the more generations of beetles occurring per year.
On Martha’s Vineyard, the southern pine beetle prefers pitch pines. An infested tree is easy to recognize. Up and down the stem, one finds orange globs of sap, sometimes referred to as “popcorn.” A close inspection of a glob will generally find a beetle stuck in the sap. This is the tree’s valiant, yet futile, attempt to ward off the infestation by “pitching out” the burrowing insect. Once the infestation is well underway, the crown of the tree turns from green to red, a clear indication that the tree is dying. The needles turn from red to brown, and then fall off the tree entirely.
Pitch pine forests already present a high risk of wildfire; a southern pine beetle infestation exacerbates that risk. In addition, once the trees have died, the dead trees also present a safety risk, as they may fall on people, structures, roads, trails, or power lines.
The recommended approach to addressing a southern pine beetle outbreak in the forest is to try to suppress the outbreak by cutting infested trees, and cutting the healthy trees in a buffer surrounding the infestation. In areas of pitch pine forests where southern pine beetles are expected, but are not yet present, thinning of the forest is recommended. Sheriffff’s Meadow Foundation is following both recommendations in its pitch pine forests. In addition, Sheriff’s Meadow is addressing the wildfire hazards and safety hazards created after the beetles have killed scores of pitch pines and have moved on to other areas.
