PINE BEETLES ALONG ALABAMA’S GULF COAST
By: Beau Brodbeck (Alabama Cooperative Extension System), Tom Ellis (Retired Forester with USFS), and Jennifer Fidler (City of Fairhope Horticulturalist)
Have you noticed all the pine trees turning bright rusty red on your drive to work? Have pine trees in your yard died? Currently southern Alabama is in the midst of a severe pine beetle infestation, which is threatening our urban forest by causing massive pine mortality throughout our area.
Each year, pines across Alabama become susceptible to pine bark beetle infestations during the long hot dry summer months. These attacks have been unusually common in the past year in southern Alabama causing cities, homeowners, and businesses to remove large numbers of dead or dying pines. This article is aimed at addressing the causes, identification, and recommended management of southern pine bark beetles in the urban landscape.
What is causing the increased pine bark beetle outbreaks?
Beetle outbreaks are generally associated with increasing tree stress. Several factors have combined over the past two years in southern Alabama to increase pine tree stress. First, the area has been impacted by a series of hurricanes, which have blasted the area with high winds, isolated salt spray, and in some cases flooding. The most widespread impact has been high winds, which have defoliated and reduced tree canopy, however, the damage hidden beneath the soil is by far the most important factor contributing to stressed trees. Often high winds rock trees damaging root systems and often severing the smaller feeder roots trees depend on for water absorption.
A second factor has been the recent drought, which has caused trees with hurricane damaged root systems, to become increasingly stressed. By some estimates, mature trees can lose up to 300 gallons of water per day from transpiration. As the summer drought lingered and high temperatures persisted, trees became increasingly susceptible to pine bark beetle infestations.
Site disturbance can also increase tree stress. Construction in and around trees often damage the roots or trunks of trees. Soil compaction (paving around trees or parking heavy equipment and materials under trees), root suffocation (placing a layer of soil over root systems will reduce airflow to roots), and physical injury (removing roots within the drip line or damaging the main stem) can greatly increase tree stress. Additionally, trees with physical injuries above ground such as lightning strikes or exposed wood attract pine bark beetles, thereby increasing the risk of infestation and mortality.
How can I tell if I have pine bark beetles?
Signs of attack are pitch tubes along the tree’s stem and yellowing to red needles in the crown. Pitch tubes are easily identified by white popcorn like spots of dried pine resin on the tree caused by the adult beetles boring into the trees. These spots occur on the main stem of the pine from the ground up into the canopy, depending on the species of pine bark beetle. These beetles lay eggs and after their eggs hatch the larvae (grubs) then make elaborate feeding tunnels through the inner bark. The tree dies as a result of the larvae girdling the tree inside the bark as well as the introduction of "blue stain" fungi which clog up the water conducting tissues of the stem. This process can be exceedingly fast often occurring inside of one week due to the high stress levels in many southern Alabama pines.
Are all pine trees susceptible to pine bark beetle?
Yes and no, while no tree is beetle proof there are certain species of pine that are less likely to become infested and die from pine bark beetles. Loblolly (Pinus taeda) and shortleaf pines (Pinus echinata) are highly susceptible to pine bark beetles and rarely survive an infestation. Longleaf (Pinus palustris) and slash pines (Pinus elliottii), however, are more resistant to pine bark beetles due to their higher sap flow, which helps repel beetles by expelling them from the tree with sap. Due to drought and lower sap flows even longleaf is having problems surviving beetle attacks and should be closely monitored in the rare case it is attacked.
What kind of pine beetle do I have?
Several species of bark beetles affect pines in Baldwin County. These include Black Turpentine Beetle (BTB), Ips engraver beetles, and Southern Pine Beetle (SPB). Attacks in pines south of Bay Minette are probably from Black Turpentine Beetles (BTB) or Ips engraver beetles. Additionally, for homeowner management options it is only important to distinguish Ips and SPB from BTB. Pines trees with BTB are generally easier to save.
The adults of BTB, Ips, and SPB all bore holes into the outer tree bark (producing pitch tubes), then lay eggs in galleries in the inner bark. The difference between these beetles are subtle, however, a few key points will help distinguish the beetles.
Black Turpentine Beetles
BTB attack from the ground up to 8 or 10 feet high on the stem.
Pitch tubes are larger than Ips or SPB and are about one inch or larger in diameter
The pitch tubes are purplish to reddish in color.
Attacks typically occur on damaged trees or on stumps of recently cut trees and may spread to adjacent trees.
- Healthy Longleaf Pine and Slash Pine often survive BTB attacks, even with no treatment. Chances of survival can be improved by immediately spraying freshly cut pine stumps, attacked trees and adjacent trees with insecticides.
Ips and SPB beetles
Attack high in the tree, often up into the crown, and nearly down to the ground
Pitch tubes are much smaller about the size of a dime
Pitch tubes are also white, yellow or reddish in color and resemble popped pop corn
Generally pines attacked by Ips or SPB beetles are doomed
If you remove dead bark the wood will have carved etchings in a “Y” or “H” shape for Ips and “S” shaped for SPB (these are caused by larva eating the cambial tissue)
What can I do to save or protect my pine trees?
In most cases it’s too late to save a tree by the time pine needles have turned bright rusty red. Unfortunately, it is often at this point that many people begin to notice that their pine has a problem. Often by the time needles have turned red the beetles have moved to neighboring trees. To prevent further beetle development it is important to detected bark beetles while trees are still green.
To attempt and save an infested tree it is essential that the problem be identified as early as possible. Make regular inspections looking for the white pitch tubes up and down the stem of your trees. Trees can be saved in some cases, more importantly homeowners can take steps to reduce the chances of beetles spreading to adjacent trees in their yards.
It is important to distinguish Slash and especially Longleaf pines from the more common loblolly pines. Longleaf and Slash are far more likely to survive beetle attacks, especially BTB. Secondly it is important to distinguish BTB from Ips or SPB because of their less severe attacks and mild impacts on longleaf pines. Below are some short and long term management strategies to help protect uninfected pines.
Short Term Management Strategy
First, identify the species of tree that is infected; longleaf is likely to survive BTB attacks.
Second, identify the type of beetle impacting your tree.
Thirdly, if the tree is dead or is severely infested, cut and remove the tree as soon as possible. It is also important to spray or grind the stump immediately. This will reduce the chances of the beetles spreading to adjacent trees. (It is important to hire a competent tree service with the proper insurance, business license, and preferably one that is International Society of Arboriculture (ISA) certified. This certification will help ensure you are dealing with a knowledgeable and professional arborist.)
Finally, use preventative sprays to protect nearby trees from beetle attacks.
Long Term Management Strategy
Maintain a healthy tree by watering regularly
Mulch the areas around your trees to help hold soil moisture
Avoid damaging the trunk or roots with lawn equipment or by building close to the tree
What preventative sprays are available?
Using preventative sprays is often expensive due to the high pressure spraying equipment needed and thus careful evaluation of the probability of infestation and the value of the trees should be considered. There is one insecticides on the market labeled for Pine Bark Beetles. This is Bifenthrin (sold as Onyx). Follow insecticide label recommendations when measuring the mixture, if incorrectly applied chemicals can be dangerous and can inversely impact aquatic life.
When spraying for BTB it is important to spray from the base of the tree to about 10 feet up the stem. Do not spray wet trees -- the bark should be dry. Apply sprays until the bark is dripping wet from about 3 feet above the highest pitch tube down to ground level.
If spraying for Ips or SPB beetle it is best to hire a professional pesticide applicator due to the need for the spray to reach from the ground well into the crown of the tree. Ips and SPB beetles often begin their infestation in the crown and move down the trunk of the tree, unlike BTB which rarely moves above 10 feet. Like spraying for BTB beetle, apply until the tree is dripping wet.
Professional pesticide applicators, using high pressure sprayers, can reach high enough in adjacent trees to limit Ips attacks, but can rarely save trees already attacked. Additionally, after carefully felling newly infested trees it is important to spray the stumps with Bifenthrin insecticides to help control beetle spread, especially if done immediately after the initial attack.
Inspect the trees at least once every two weeks for evidence of new attacks and continue inspecting for a period of one year. Spray the trees again when new attacks begin. The total number of sprays, frequency of spraying, and application methods may be legally limited, be sure to check the insecticide label.
If you have any further questions contact the Alabama Cooperative Extension System at 251-937-7176.