If you believe you have found susceptible host trees killed by southern pine beetle in Massachusetts, please report their location, here: https://survey123.arcgis.com/share/688810dbaae1430f86b595c1c57daf5c . The southern pine beetle (SPB) undergoes complete metamorphosis (is holometabolous) with four life stages: egg, larva, pupa, and adult. Adults are dark red/brown to black in color and 1/16 – 1/8” in length. Eggs are white and larvae are crescent-shaped with a dark red/brown head and a white body. Four larval instars are present, with pupa being bright white. The adult is light brown in color prior to drying and hardening and becoming darker in color. Female beetles will select suitable host trees and release chemical pheromones to attract male mates. She will penetrate the bark and begin creating a gallery where she is joined by the male and mates. Early attacks to the tree may be “pitched out” by the resin defenses of the tree. The pheromones produced by the females and the volatile chemicals expressed by the stressed host plant will attract additional males and females. If tree defenses can be overcome, females will colonize beneath the bark, creating S-shaped galleries. The inoculation of the tree with a blue stain fungus as well as other fungi occurs with colonization of southern pine beetle, however, it is the act of "mass attack" by the insects themselves which leads to tree mortality. Entomocorticium spp. symbiotic fungi are associated with southern pine beetles and the immature larvae feed on this fungus. Females may lay up to 160 eggs in their lifetime and development can take as little as 26 days in warmer climates. In the south, 3-9 generations of SPB have been observed to occur per year. In NY, 3-4 generations have been observed on Long Island. Current Massachusetts temperatures should keep the number of generations per year to the lower end of this range.
Southern pine beetle can be detected most easily by the presence of popcorn-sized pitch tubes on the outer bark of trunks and branches. Pitch tubes can range in color from white to red. They can occur from the ground level to high in the canopy of the tree. Exit holes (about 1/16” in diameter) can be observed in the bark from emerging adults. S-shaped galleries can also be observed by peeling back any bark that may be falling off the tree. Brown-orange frass (excrement) that looks like wood shavings is found packed within the galleries. By the time foliage fades from green to yellow to brown, the infestation may be advanced. The presence of certain checkered or clerid beetles can also indicate high populations of southern pine beetle, as these checkered beetles prey upon SPB. Southern pine beetle prefers trees damaged by lightning strikes or fire. In the southeastern part of the insect's range, southern pine beetle is not known to preferentially attack drought stressed or chronically stressed trees. Trees under 15 years of age or 2 inches in diameter may be seldom attacked.
Aerial surveys (from aircraft) can be employed to look for southern pine beetle killed trees in forested locations. Trees can then be ground-truthed by land managers to see if southern pine beetle is the causal agent of mortality. Southern pine beetles can also be trapped using pheromone (sexually attractive) and kairomone (host plant volatile) chemicals. Female pheromones (frontalin) and male pheromones (endo-brevicomin) as well as kairomones such as alpha-pinene and others can be included with flight intercept funnel traps and can be used to monitor for southern pine beetle. (Some research suggests placing the male pheromone a short distance from the trap itself to increase efficacy).
The silvicultural management of southern pine beetle in forested stands will not be discussed as a part of this management guide. However, such best management practices in forest stands do exist.
In urban or ornamental landscape settings, maintaining a distance of at least 25 feet between susceptible hosts can help reduce or prevent the likelihood of southern pine beetle attack. Promoting tree species diversity in the landscape is also a helpful cultural management practice. Remove damaged host plants (lightning struck trees, those damaged by heavy equipment or construction) immediately if in an area where southern pine beetle outbreaks are known to occur. Avoid accidental damage to susceptible hosts and minimize the potential for construction damage.
If an active infestation of southern pine beetle is occuring, it is recommended to cut and remove any actively infested trees as soon as possible. If removal is not an option, it is still recommended to cut and fell infested trees as this practice has been found to reduce larval survival (Swain and Remion, 1981; Coulson and Klepzig, 2011). If possible, remove the bark of felled trees or chip the entire tree. Inactive trees (trees from which southern pine beetle has already developed and emerged) can be left at the site in order to encourage the presence of natural enemies (Turchin et al., 1999).
Predaceous clerid beetles (checkered beetles) are some of the most important natural enemies of the southern pine beetle, including Thanasimus dubius. Adult T. dubius are attracted to trees being killed by mass attack by the southern pine beetle. Adult T. dubius will feed on adult southern pine beetles, and the larval clerid beetles will attack the larval or immature southern pine beetles beneath the bark. A species of longlegged fly (Medetera bistriata) is also known to be a significant natural enemy of the southern pine beetle. This fly will lay its eggs near southern pine beetle gallery entrance holes and the fly larvae will enter them in order to attack the immature life stages of SPB. Pupation of this fly species likely occurs on the host plant bark surface. Downy, hairy, and pileated woodpeckers (Picoides pubescens, P. villosus, and Dryocopus pileatus) are also known to be significant predators of the southern pine beetle. Some research has shown woodpecker densities to increase over a 10 year period of southern pine beetle infestations (Reeve, 2011).
Abamectin (L)
Beauveria bassiana (NL)
Bifenthrin (NL)
Cyantraniliprole (NL)
Emamectin benzoate (L)
Flonicamid+cyclaniliprole (N)
Isaria (paecilomyces) fumosoroseus (NL)
Lambda-cyhalothrin (L)
Neem oil (NL)
Permethrin (L)
Tau-fluvalinate (NL)
Systemic injection of emamectin benzoate has been found to be effective (Grosman et al., 2009). Contact insecticide applications need to be made preventatively in order to reach southern pine beetle adults before trees become infested.
Active ingredients that may be applied systemically include: abamectin (injection), cyantraniliprole (soil drench, soil injection), neem oil (soil drench), and emamectin benzoate (injection).
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
