Understanding Bark Beetle Infestations: Prevention and Solutions
Bark beetles are small insects, but don’t let their size fool you.
The strong jaws of these beetles chew and create a buckshot pattern of holes on the bark surface of infested branches or trunks of trees, causing widespread mortality in forests and forested communities. About the size of a grain of rice, most species have hard, cylindrical bodies that are dark red, brown, or black.
Native bark beetles cause high levels of tree mortality in California and elsewhere. The extent of mortality is primarily influenced by forest stand and drought conditions. During a period of inadequate precipitation, a dramatic rise in dead trees is likely. Dense groups of trees are particularly susceptible to bark beetle attacks due to stress caused by limited resources. The main species include mountain pine beetles, fir engraver beetles, western pine beetles, Jeffrey pine beetles, and ips (also called pine engraver) beetles.
An Aerial View of a Forest Damaged by Bark Beetles
Impacts of Infestation
Under outbreak conditions, the sheer number of beetles can overwhelm the tree's defenses with resulting impacts on the lumber industry, water quality, fish and wildlife, and property values. The reproductive cycle of bark beetles is particularly alarming because it allows for rapid population growth under the right conditions. They typically have several generations within a year, especially in warmer climates, which compounds their impact on forested areas. Early detection is key to preventing widespread tree loss; this involves regular monitoring of tree health and immediate action when signs of infestation are observed.
Severe infestations can also lead to substantial economic losses in urban management, forestry, and the lumber industry. The loss of trees in urban areas can decrease property values and increase city temperatures, leading to higher energy costs.
Signs of Bark Beetle Activity
Pine Tree Bark Showing Signs of Bark Beetle Activity
Bark beetle infestation is easily spotted. Bark beetle activity starts on the bark surface and extends to the inner bark of twigs, branches, or trunks. A living tree can be killed by the feeding activity of adults and larvae, which damages the phloem in such a way that the tree is girdled. The beetles also introduce several species of fungi which invade and infect the wood. The first sign of a bark beetle infestation in a tree may be the discoloration of the needles that occurs when fungi block the xylem and prevent water transport to the foliage.
The following are additional signs that a tree may be infested by bark beetles:
In the Bark
- Trees react by releasing pitch as their natural defense against bark beetle attack. A white pitch tube means the beetle was successfully repelled by the tree. If the pitch tube is reddish brown, most likely the beetle was successful in attacking the tree.
- The pitch is accompanied by a sawdust-like substance, called "frass," created by bark beetles and their larvae as they bore through the bark.
- Frass has accumulated in tree crevices and may have fallen to the ground, resembling very fine reddish-brown coffee ground material at the base of the tree.
- Bark flaking or holes in the bark caused by woodpeckers foraging for bark beetles are also a good indicator that bark beetles are present.
- Removing bark sections will reveal holes created by bark beetles as well as dead or degraded inner bark.
On Leaves or Needles
- The needles on conifer trees, like pines, begin to turn a reddish-brown color. Often the change begins at the tops of the trees and moves down.
- Some trees may slowly fade in color from green to brown.
- Some trees may die within a few weeks of infestation but may not show yellow-green, fading, or red foliage for several months. Other types of trees may survive for years before dying; by the time a tree appears dead, it cannot be saved.
Ecological Importance
Ecologically, bark beetles play a role in forest dynamics by promoting the renewal of forests through the decomposition of dead and dying wood. However, when their populations are unchecked, they can cause the loss of biodiversity and disrupt local ecosystems. Effective management strategies are therefore crucial not only for preserving landscape aesthetics but also for maintaining ecological balance and supporting local wildlife.
Though most species of bark beetles live in dead, weakened, or dying specimens, some species attack and kill live trees. A few species are aggressive and can develop large populations that invade and kill healthy trees and are therefore known as pests.
Preventative Measures and Treatment Options
A Mountain Pine Beetle, Which Can Devastate Forests - Photo by Egor Kamelev
To combat the destructive nature of bark beetles, it is essential to consider both preventative measures and direct treatment options. Preventative measures include maintaining tree health through proper watering, mulching, and pruning practices. Stressed trees are more susceptible to infestation, so improving tree vigor is a proactive way to ward off beetle attacks. Additionally, removing infested trees and debris can help prevent the spread of beetles to healthy trees.
For direct treatment, insecticides can be effective, but they must be applied at specific times during the beetle's life cycle. Biological control methods, such as introducing natural predators of the bark beetle or using pheromone traps, are also discussed as environmentally friendly options. It's important to consult with a professional arborist to choose the most appropriate treatment plan based on the specific conditions and beetle species involved.
Arborist Now's Role in Managing Bark Beetle Infestations
At Arborist Now, we are committed to protecting the San Francisco Bay area's trees from pests like bark beetles. Our team of certified arborists is equipped with the latest tools and knowledge to diagnose and treat bark beetle infestations effectively. By choosing Arborist Now, you benefit from comprehensive tree care services that include regular health assessments, tailored treatment plans, and preventative care advice to keep your trees healthy and vibrant. We are experienced in finding and treating problems created by pests and diseases that can decimate the trees on your property.
We understand the importance of maintaining a healthy urban forest for future generations. Contact us today to learn how our expert services can help preserve your landscape and protect it from the threat of bark beetles and other pests. Your trees are an invaluable asset to your community; let's work together to keep them healthy and thriving.
Originally published on April 21, 2017.
