Pine Tree Decline is a Common Issue
The UF/IFAS Flagler County Extension Service receives at least three calls a week concerning the health of declining pine trees. What is killing these trees? The answer is a little more complicated than it may first appear. Pines are susceptible to wind damage, root damage, and insects and pathogens. Many times trees that are injured will begin to also show signs of insect infestation. Decisions to apply pesticides should take all things into consideration.
Pine Trees Can Suffer Unseen Damage During Storms
Pine trees are not as resistant to strong winds as some other types of trees, for example live oaks. Lone pines are more susceptible to wind damage and failure during hurricanes due to a buffering effect from trees that are planted in groups or were left together during initial site clearing. Pine trees that survive hurricanes may not show any immediate signs of damage, but then decline over the next year to two. The reason for this decline is suspected to be internal damage to the trunk above ground, and delicate roots below ground. This damage causes stress that makes the tree more attractive to wood boring insects and susceptible to pathogens. For more information, please visit “Wind and Trees: Lessons Learned from Hurricanes”,
Compaction Can Damage Roots
During site clearing tree roots should be protected by creating a large fenced area around the roots to avoid compaction caused by equipment. Excavation near trees can also damage roots. Trenching severs many roots, including large diameter roots that can lead to tree failure. The best way to dig around a tree’s roots is with an air spade. Construction for driveways, sidewalks, and other hardscape can sever tree roots on one side of a tree, not only negatively affecting tree health, but also creating an unstable tree that could fall due to high winds.
Stressed Trees are Attractive to Insects
Pine trees can be stressed from human activities or due to natural causes, but regardless of the reason, the stressed tree is more susceptible to insect infestation. Color change or partial needle loss are common, and may not be a sign anything is wrong. Rapid color change accompanied by sawdust and resin on the tree trunk could require quick action. In Florida we have two basic classes of pine beetles, epidemic and non-epidemic beetles. As the names imply, the non-epidemic beetles don’t usually spread to neighboring pines. These include pine engravers, black turpentine beetles, and a few other wood boring species. Decision making to remove pines should be based on the number of adjacent pines that are threatened. A lone pine presents little threat due to the lack of adjacent trees.
Southern Pine Beetle?
Southern pine beetle (SPB) are considered epidemic due to their capability to spread to neighboring trees. SPB are actually relatively rare. Infestations are detectible by hundreds of popcorn like white balls of resin exuding from the tree trunk. Immediate removal is recommended for positively identified southern pine beetle infested pines. Consideration should also be given to removing adjacent pines even if no obvious signs of infestation are present. For more information, please visit “Southern Pine Beetle, Dendroctonus frontalis Zimmermann (Insecta: Coleoptera: Curculionidae: Scolytinae)”.
Insecticidal treatments are not effective for trees that are already heavily infested. Preventative applications are only recommended for high value healthy pine trees. Injections of insecticides may not work because the vascular tissue of the tree is already compromised by pathogens and the infestation. Applications of insecticides can actually kill many beneficial predators of bark beetles making the problem worse over time.
Decisions about Removal and Treatment
Making decisions about pine tree removal and/or treatment can be complex. Many pines in our area are still showing lasting effects from hurricanes Matthew and Irma. Proximity of trees to the home and the number of trees growing together can impact decisions. Pesticide applications should be reserved for a very narrow window of situations. Most issues that are not southern pine beetle related will work themselves out over time as weaker trees die off. Care should be taken to protect tree roots and trunk from damage during construction and site clearing. If possible pines should be left in groups to increase wind resistance. For a full list of pine bark beetle infestation symptoms and suggested actions to take please visit “My Pine IS Under Attack-What Should I Do?”