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"Pine bark beetle" is a broad term used to describe several species of native Dendroctonus beetles that cause mortality in pine trees. Pine Bark Beetles are typically attracted to stressed pines, and once established, can infest healthy neighboring trees. Pine bark beetles can become a major concern in urban forests during droughts, following hurricanes or as a result of root damage or poor growing conditions. Beetles can impact vast numbers of trees and potentially devastate large acreages if left unmanaged.
In the urban forest the management techniques for controlling beetles are different that those implemented in rural timberlands due to the higher values and removal costs of landscape pines. This publication is aimed at addressing the causes, identification, and recommended integrated pest management techniques for pine bark beetles in the urban landscape.
What attracts pine bark beetle?
Pine bark beetle are attracted to stressed pines with declining health. Common stressors in the urban forest include:
Several species of bark beetles affect pines in southern urban landscape. These include the black turpentine beetle (BTB), Ips engraver beetles, and the southern pine beetle (SPB). For homeowner management options it is most important to distinguish Ips and SPB from BTB. Both Ips and SPB beetles introduce blue stain fungus which cannot be treated and will often result in tree mortality. BTB seldom carries the fungus and as result does not always kill trees. It is important to note that more than one species of beetle can be found in an infested tree.
The difference between these beetles are subtle, however, a few key points will help distinguish the beetles.
Black turpentine beetles
In most cases it's too late to save a trees once they have been infested, with the possible exception of BTB. Instead management is aimed at preventing the spread of pine bark beetles. While pine beetles are not great flyers and cannot buzz from an infested tree in your front yard to one in the backyard, they can easily glide to neighboring pines. Trees standing in close proximity or within 20 yards of an actively infested tree are at greatest risk.
Begin by make regular inspections looking for the pitch tubes up and down the stem of your pines, especially those trees that have undergone one of the previously mentioned stressors (construction damage, lightning strikes or during drought). Once beetles have been identified use the following integrated pest management short and long-term management strategies:
Short Term Management Strategies:
Short term strategies are meant for dealing with currently infested trees and preventing the spread of the pest.
Long Term Management Strategies:
Long term strategies are meant for ensuring the future health of the tree to reduce stressors which attract pine beetle outbreaks.
There are several contact pesticides labeled for pine bark beetle prevention. These include Bifenthrin, Permethrin and Carbaryl. If pesticides are used, high risk trees should be sprayed in late winter or early spring before beetles become active. High risk trees include: trees adjacent to infested areas, trees with root or above ground damage and lightning struck trees.
Each of these pesticides is sprayed on the trunk of the pine. This can pose some challenges on large trees as the entire trunk from the ground to the lower canopy must be sprayed to effectively prevent Ips and SPB attacks on high risk trees (these beetles often start in the canopy and move downwards). This will require the use of either a high pressure sprayer or a bucket truck to reach the canopy of larger pines. For BTB beetle only the bottom 12 to 15 feet should be sprayed. This method provides between 1 to 3 months of protection depending on the product and weather conditions.
Pesticide drift, non-target species toxicity (pollinators, aquatic species, etc.) and applicator safety are concerns and thus the use of a professional applicator is highly recommended. Also, some formulations of these chemicals are restricted use. Always carefully read and follow label recommendations when measuring and applying pesticides.
Injectable systemic pesticides:
There are several injectable pesticides labeled for pine beetle use. While this approach removes many of the challenges associated with the contact applications, it does require a professional arborist to drill into the base of trees and macro-infuse the tree. Injections are not recommended during periods of drought or for severely stressed trees as the system relies on the tree's vascular system to translocate the product throughout the tree. It should be noted this technique is invasive to the tree and there is a risk of introducing fungal decay. However, these technique do provide longer protection and avoid many of the non-target species and applicator safety concerns.
An alternative to pesticide use are the anti-aggregate pheromones, such as Verbenone, that help disperse adult beetles. Pine beetles naturally produce pheromones to communicate and attract or disperse beetles. Verbenone is a synthesized anti-aggregate that is packaged in slow-release pouches that are stapled to trees at risk from pine beetle infestation. Like pesticides this is only a preventative treatment. Also, research has found this product to exhibit mixed results and it's generally considered to be less effective than pesticides.
Arnold “Beau” Brodbeck, PhDAlabama Cooperative Extension System251.firstname.lastname@example.org
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