There is a steady discussion among homeowners, arborists and tree companies that has become more frequent over the last few months. People are noticing dying pines on Jekyll Island, Sea Island and St. Simons Island. As in most cases, homeowners don’t see the problem until needles turn bronze and start to fall. By then, the culprit has moved along to a neighboring pine. The culprit is one of five beetles known to have invaded the islands, the Southern Pine Beetle (SPB), the most destructive insect of native pine of pine in the southern United States; the Black Turpentine Beetle (BTB) and three species of IPS (bark or engraver) beetle. The first wave of SPB attacked in 2014 in three locations on St. Simons Island-Musgrove Plantation, Cannons Point, and Sinclair Plantation. Now in 2018, beetle damage (species not confirmed) is being seen in other locations including Sea Palms West, and various locations on Sea Island.
The Southern Pine Beetle is native to the United States. Mature adults are brown to black in color; younger adults change from yellowish-white to yellowish-brown to reddish-brown to dark brown. The beetle has short legs, a body length of 2-4 millimeters and a rounded rear end. The female is the initial invader, responsible for the choice of the tree. Able to fly up to 2 miles (further with a strong wind), she selects a diseased or wounded tree, and bores under the bark to begin the construction of a gallery in the phloem (nutrient conducting) tissue. She then emits a very strong pheromone that attracts both male and females to the tree, creating a mass attack. Increasing numbers of the beetles then become capable of overwhelming the only means of defense used by healthy, vigorous trees, the excretion of resin to entrap or repel the beetle. Healthy trees then become victims. When the beetle count is high enough, the human ear can hear the chirping noise that the beetles make when communicating among themselves.
Mating occurs after infestation and the burrowing beetles make many more galleries. These are soon filled with frass (excrement) and boring material. Up to 30 eggs are laid in little niches found along the length of each gallery. Eggs hatch within three to nine days. Both adults and offspring feed on the phloem tissue of the tree, creating winding S-shaped or serpentine galleries so extensive that the tree is girdled. The legless larva will go through three larval states, munching their way through the pine, eventually reaching the outer bark where each grub will form the final pupal stage. In five to 17 days, the insects turn into adults, remaining under the bark for another six to 14 days, while their cuticle hardens and turn to the mature brown to black color. They then bore out of the outer bark, leaving an open shot hole behind, flying immediately to attack another tree. They leave behind a dead tree. The cycle from egg to adult can be anywhere from 26 to 60 days, with as many as nine generations occurring in a year.
In addition to the destruction their feeding causes, the beetles carry blue-stain fungi which when introduced into the pine tree, clog the xylem (water conducting) tissue of the tree. Once the beetles colonize a tree, the tree is doomed; no control measure is effective. The only solution is to remove the infected trees and create a virtual distance from the infected areas and other remaining unaffected stands. Left uncontrolled, infestations can take over thousands of acres in forests, parks and even home yards.
The first sign of the beetle is the presence of orange-brown boring dust and tiny white pitch pellets at the base of the tree, or in crevices of the bark. Also easily seen are multiple popcorn-size lumps of pitch (pitch tubes) on the outer part of the pine stems. Sometimes the round shot-like holes left by emerging adults can be seen. Infested trees will show noticeable foliage discoloration from green to yellow to red. By the time the foliage is brown, the beetles may have already come and gone. Removing the outer bark, which will uncover the winding S-shaped galleries that cross over each other, will provide the most positive diagnostic sign of Southern Pine Beetle.
Is there any way to stop the spread of the voracious beetles? Keep your pines healthy! Remove any wounded, sick or lightening-struck pines immediately, because the beetles’ preference is to move in and attack the sick and the weak ones first. In new home construction, keep the soil from being compacted by heavy equipment, and also prevent any grade change to existing roots. Be vigilant in observing the health of older mature pines particularly if construction occurs in the summer months. Any sign of pitch tubes, feeding galleries under the bark, or fading tree foliage means beetles have arrived! Remove the pine as soon as possible because once infiltrated, nothing will stop the death of the pine but you might be able to prevent emerging adult beetles from flying over to the next pine. In established landscapes, water pines during dry spells and fertilize them as needed. Generally, this requires two pounds of a complete fertilizer such as 10-8-6 for each inch of tree diameter on mature trees, and just one pound on pines less than six inches in diameter.
According to Rog Ditmer, a professional certified arborist with risk management training, highly valued healthy mature pines or those with very early infestations have benefited from a trunk injection of Emamectin Benzoate. As a professional, Rog has to assess each situation and ask: How long ago was penetration? By how many beetles and what species of beetle? Is the tree healthy or stressed? Is it surrounded by other infected trees and in the swath of moving advancement or does the tree stand alone as an isolated case? Is the tree an important landscape investment or will it go unnoticed if lost? If this costly treatment is deemed warranted after a thorough assessment, a trunk injection is done; this can be effective for up to three years.
According to the Georgia Forestry Commission, application of Onyx™ or Bifen XTM™ by spraying on an urban ornamental pine tree for IPS and BTB must include the entire trunk of an insect-free tree, from the base and reaching to at least halfway into the live crown. The site claims that spraying can be effective for up to six months. However, the spray has better effect on some beetle species but not all (once again taking in all the questions mentioned above).
With relatively low cost, it is at least worth the effort. Onyx™ can also be used to kill emerging beetles on infested ornamental pine trees if they can’t be removed quickly but requires the spraying of the entire tree, a method not recommended on small lots in urban settings.
Please note: A licensed, insured professional should be hired to make applications both into the trunk or when spraying high into the tree canopy; specialized equipment is necessary and the risk of chemical drift when spraying must be minimized.