Seattle’s skyline is famous for its mix of modern architecture and towering evergreens. But our city’s conifers are more than just a beautiful backdrop – they’re a vital part of our ecosystem and urban identity.

Unfortunately, these important trees face a growing threat: bark beetles. These tiny insects are causing big problems, especially as our region experiences more frequent droughts due to climate change. In this post, we’ll explore the bark beetle issue, its connection to recent weather patterns, and how you can help your beloved conifers to thrive in the face of adversity.

Key Takeaways

• Bark beetles are threatening Seattle’s conifers, with drought conditions making trees more vulnerable to infestation.
• Look for signs like small holes in bark, sap tubes, red-orange dust on tree bark, and discolored needles.
• Preventive treatments offered by Seattle Tree Care can effectively protect trees from bark beetle attacks, keeping them healthy and strong.
• Deep root watering using specialized equipment helps trees stay healthy and resistant to beetle infestations by reducing drought stress.
• Regular tree care practices like proper mulching, pruning, and monitoring are important for maintaining tree health and preventing beetle problems.

Understanding Bark Beetles

Bark beetles are small insects that burrow into tree bark to lay their eggs. While they’re a natural part of forest ecosystems, certain conditions can lead to harmful infestations. In Seattle, we commonly see several types of bark beetles, including:

1. Douglas-fir beetle
2. Spruce beetle
3. Pine engraver beetle

These beetles attack different conifer species, but their method is similar. They bore through the outer bark and create tunnels in the phloem – the layer just beneath the bark that transports nutrients throughout the tree. As the beetles dig these galleries, they destroy the tree’s vascular system, interrupting the flow of water and nutrients. This eventually starves and kills the tree.

A few beetles won’t usually harm a large, healthy tree. However, when trees are stressed or when beetle populations surge, the damage can be severe and even fatal.

The Growing Problem

In 2021, more than half of tree mortality across Washington’s forests were caused by the various species of bark beetles. And the Puget Sound region saw higher concentrations of Douglas-fir beetle-caused mortality compared to the rest of western Washington.

But why is bark beetle increasing? More frequent and prolonged periods of drought.

Drought conditions, which are becoming more common due to climate change, have put our trees under more stress than ever before. Drought-stressed trees are like a welcome mat for bark beetles. Here’s why:

• Weakened defenses: Healthy trees produce sap to push out invading beetles. Drought-stressed trees can’t produce enough sap for this natural defense.
• Chemical signals: Stressed trees release chemicals that actually attract bark beetles.
• Reduced resistance: With less water and nutrients during time of drought, trees have a harder time fighting off beetle attacks.

As droughts become more frequent and intense, we’re seeing more trees fall victim to bark beetle infestations. This creates a vicious cycle: more successful beetle attacks lead to larger beetle populations, which then attack more trees.

Red-orange boring dust caused by Douglas-fir beetles | Sandy Kegley, USDA Forest Service, Bugwood.org

Signs of Bark Beetle Infestation

Catching a bark beetle problem early can make a big difference in saving a tree. Here are some signs to watch for:

• Small holes in the bark: These are entry and exit points for the beetles.
• Pitch tubes: As beetles bore in, trees try to push them out with sap. This can create small tubes on the bark made of red resin mixed with bark and wood borings (most commonly seen on pines).
• Discolored needles: Infested parts of the tree may have yellowing or browning needles.
• Peeling bark: In later stages, bark may become loose and fall off.
• Woodpecker activity: These birds feed on bark beetles, so increased woodpecker attention can be a sign of infestation.

If you notice these signs on your trees, it’s important to get professional help quickly.

Watch our video below for more information on bark beetles.

The Impact on Seattle’s Urban Forest

Bark beetle infestations can have wide-reaching effects on our urban environment:

• Tree loss: Severe infestations can kill trees, changing the landscape of our neighborhoods and parks.
• Reduced air quality: Fewer trees in our busy city can mean less air filtration and oxygen production.
• Increased urban heat: Trees provide cooling shade. Losing them can increase the urban heat island effect, making our city hotter.
• Habitat disruption: Many animals that local residents appreciate rely on our urban trees for food and shelter.
• Property value: Mature trees can boost property values. Losing them can have economic impacts.
• City character: Our evergreen canopy is part of what makes Seattle special. Losing it would change the look and feel of our city for the worse.

Prevention and Treatment

The good news is that we’re not helpless against bark beetles. There are effective ways to prevent and treat infestations:

Preventive Treatments

Seattle Tree Care offers a highly effective preventive treatment for bark beetles. To prevent infestation, we apply a special insecticide as an injection into the trunk and the vascular system of the tree. This kills beetles as they try to bore into the tree. This treatment is:

• Long-lasting: It can protect trees for up to a year.
• Safe for the tree: It doesn’t harm the tree.
• Targeted: It specifically targets boring insects, not beneficial insects or pollinators, so it’s not harmful to local ecosystems.

For high-value trees or those in areas with known beetle problems, this preventive treatment can be a game-changer, especially as bark beetles can spread so rapidly during drought.

Early Detection and Response

If you spot signs of bark beetles, quick action is key. Seattle Tree Care can:

• Assess the extent of the infestation
• Apply targeted treatments to stop the beetle attack
• Help stressed trees recover with proper care

Sometimes, removal of heavily infested trees is necessary to protect nearby healthy trees. If this is the case, we can safely remove the tree and advise on replanting options.

Drought Management: Deep Root Watering

One of the best ways to protect trees from bark beetles is to keep them healthy and stress-free. And the most important way to do that is to ensure your conifers get the water they need during times of drought. In our ever hotter and drier summers here in the PNW, we need to be caring for urban and suburban trees by providing supplemental water.

You can do this by watering trees deeply but infrequently. You want to water enough to allow the roots to receive moisture deep below the surface. But you don’t want to water too frequently so that you create a root rot problem or attract fungal diseases.

The best method is the use of soaker hoses rather than sprinkler systems. Soaker hoses slowly wet the soil, allowing water to reach deep down into the roots without runoff or excessive evaporation.

The Benefits of Deep Root Watering

Because watering your trees during times of drought can be time-consuming, our tree health experts here at Seattle Tree Care have devised a solution. We’ve invested in a new, specialized truck to efficiently provide Seattle residents with deep root watering. This service is especially valuable during drought conditions. Here’s how it works:

The truck is equipped with a high-pressure system that can deliver water directly to the tree’s root zone. We use a probe to inject water deep into the soil, where the tree’s main roots are.

This method is more effective than surface watering because it:

• Reduces water waste through evaporation
• Encourages deeper root growth, which allows trees to better cope with drought conditions in the future
• Helps wash away salt buildup in the soil
• Can deliver fertilizers or treatments along with the water

Regular deep root watering can help trees stay healthy and resistant to bark beetle attacks, even during dry spells. If you want to outsource your watering to us, to keep your conifers and other trees healthy during times of drought, just call us at 206-789-0534 today to get on our schedule.

Additional Tree Care Tips

Beyond professional treatments, there are more summer care tips you can use to keep your conifers healthy and make them less attractive to bark beetles:

• Mulching: Apply a layer of organic mulch around the base of your trees. This helps retain soil moisture and regulate temperature.
• Proper pruning: Remove dead or damaged branches, but avoid unnecessary pruning during peak beetle season (usually spring and early summer).
• Avoid root damage: Be careful not to injure tree roots during yard work or construction.
• Diversify: When planting new trees, choose a mix of deciduous and evergreen species to reduce the risk of widespread pest damage.
• Monitor: Regularly check your trees for signs of stress or pest infestation.

Take Action Against Bark Beetles

Bark beetles pose a real threat to Seattle’s iconic conifers, especially as the drought problems get worse and worse in the PNW. But by building awareness, prioritizing early detection, and applying preventative treatments, we can protect our important evergreens.

Seattle Tree Care is committed to preserving our city’s trees. If you have conifers on your property, don’t wait for signs of trouble – call Seattle Tree Care today at 206-789-0534 to schedule an inspection and take steps to protect your trees.