Douglas Fir Pitch Moth: Essential Facts and Tips

Douglas Fir Pitch Moth is a native species found in mixed-conifer forests throughout the western United States and southern British Columbia. These moths are known for causing damage to the Douglas-fir, spruce, and true fir trees by feeding on their foliage. Understanding the life cycle, biology, and management methods of the Douglas-fir pitch moth is essential for keeping your trees healthy and minimizing the impact of these pests on your landscape.

The life cycle of the pitch moth typically requires two years to develop from egg to adult, though the exact time of emergence varies. In some cases, adults can emerge at different times, making the moth’s population more widespread and difficult to manage. To help prevent damage caused by the pitch moths, it is crucial to keep your trees healthy and identify possible infestations early on.

Some signs of a Douglas-fir pitch moth infestation include yellow spots on needles, reddish-brown patches, and needle loss. When an infestation is identified, various approaches can be undertaken to manage the situation, such as ensuring proper tree hydration and employing pest management techniques. Early detection and appropriate action can significantly decrease the impact of the pitch moth and maintain the health of your trees.

Douglas Fir Pitch Moth: An Overview

Identification of the Douglas Fir Pitch Moth

The Douglas Fir Pitch Moth is a clearwing moth belonging to the species Synanthedon sequoiae. This moth is known for its striking appearances, with a wingspan ranging from 1 to 1.5 inches. Key features of the Douglas Fir Pitch Moth include:

  • Transparent wings with dark borders
  • Black and yellow bands on the abdomen
  • Antennae with a comb-like appearance

Biology and Life Cycle

The life cycle of the Douglas Fir Pitch Moth is quite similar to that of the Sequoia Pitch Moth. The development process takes about two years, from egg to adult. Key stages of the life cycle are:

  • Egg-laying on the bark of Douglas-Fir trees
  • Larvae feeding on tree roots, followed by pupation
  • Adult moths emerging from pupae, with variable emergence times

Douglas Fir Pitch Moths and Sequoia Pitch Moths share similarities in their biology and management practices. However, Douglas Fir Pitch Moths are typically not managed in landscapes, unlike Sequoia Pitch Moths.

Comparison Table: Douglas Fir Pitch Moth vs. Sequoia Pitch Moth

Feature Douglas Fir Pitch Moth Sequoia Pitch Moth
Life cycle Two years Two years
Host tree Douglas-fir Sequoia
Wingspan 1 – 1.5 inches Similar to Douglas Fir Pitch Moth
Management Not commonly managed Managed in landscapes

Understanding the biology and life cycle of these moths is vital for guiding appropriate management practices and ensuring healthy forest ecosystems.

Damage and Infestation

Signs of Infestation

The Douglas Fir Pitch Moth causes damage to conifers, particularly the Douglas Fir. The larvae bore into the tree bark, causing the tree to produce excessive amounts of resin. Some indicators of infestation include:

  • Resin globs: Found around branch scars, pruning wounds, and other weak points
  • Exit holes: Adult moths leaving the tree after their larvae stage
  • Frass: Sawdust-like material ejected by larvae while feeding on the tree

Areas at Risk

Douglas Fir Pitch Moths are commonly found in the following regions, where they infest Douglas fir, spruce, and other conifers:

  • Oregon
  • California
  • Washington
  • British Columbia

Damage caused by Pitch Moths can vary. In most cases, they don’t significantly harm the tree. However, excessive infestations may weaken trees, making them susceptible to other pests or diseases.

Prevention and Control

Cultural Practices

One way to prevent and control Douglas-fir pitch moth infestations is through cultural practices. Properly maintaining the health of your fir trees can deter pests and reduce vulnerability. For instance:

  • Prune branches only during the dormant season to avoid attracting the moths
  • Avoid injuring trunks and branches as pitch moths are attracted to pruning wounds

Pheromone Traps

Another method to prevent and control Douglas-fir pitch moth is using pheromone traps. These traps attract and capture male moths, reducing the mating potential and eventually decreasing the population.

Pros:

  • Pheromone traps are non-toxic and environmentally friendly
  • They are species-specific, targeting only Douglas-fir pitch moths

Cons:

  • These traps should be used alongside other prevention methods for a complete approach

Insecticides

In certain cases, insecticides can be used as a control measure. However, they should be applied with caution and only when absolutely necessary. Insecticides can be harmful to beneficial organisms, the environment, and humans.

Table: Insecticide Comparison

Insecticide Type Pros Cons
Contact Faster acting, broad-spectrum Can harm non-target species, shorter residual
Systemic Longer lasting, target specificity Slower acting, potential for environmental harm

In summary:

  • Cultural practices: healthy trees, pruning during dormant season, avoid injuries
  • Pheromone traps: environmentally friendly, species-specific
  • Insecticides: use with caution, consider contact or systemic based on situation

Additional Concerns and Considerations

Impact on Christmas Tree Industry

The Douglas-fir pitch moth can negatively impact the Christmas tree industry due to its impact on the appearance and health of trees. It can cause deformations of branches:

  • Reduced density of needles
  • Formation of pitch masses on branches

Christmas tree farmers should monitor their trees for signs of infestation, particularly from June to July, when the yellowjacket wasp can spread these moths.

Association with Other Pests and Diseases

Douglas-fir pitch moths are often linked with several other pests and diseases affecting Douglas-fir, pine trees, and hemlocks including:

  • Douglas-fir tussock moth
  • Western gall rust
  • Laminated root rot
  • Mistletoe

Each of these pests and diseases has a unique set of characteristics and manifestations:

Pest/Disease Characteristics
Douglas-fir tussock moth Feeds on needles, causing defoliation; produces a distinct cocoon
Western gall rust Causes swollen, gall-like growths on branches
Laminated root rot Leads to root decay, tree death, favoring wet/saturated soil
Mistletoe Parasitic plant that weakens trees due to nutrient loss

To mitigate the risk of these pests and diseases, it is crucial to maintain proper tree care, including a suitable soil pH, appropriate watering, and monitoring for signs of infestation such as yellow jackets in June and July. Oregon State University and UC IPM provide valuable resources for identification and management of these challenges.

Additionally, farmers should avoid overwatering, which can create a favorable environment for diseases like laminated root rot. Many of these problems can be managed through a combination of physical and chemical control methods. Monitoring and timely intervention at the appropriate stage of pest or disease development is crucial for ensuring the health and vigor of trees.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Douglas Fir Pitch Moth

 

lobster/butterfly?
Location: Redmond, WA
June 26, 2011 1:21 pm
Hey, I found this flying creature at work and was really curious as to what it is. It looks like a lobster crossed with a butterfly.
Signature: Joe

Douglas Fir Pitch Moth

Hi Joe,
We could have easily given you a general family name of Sesiidae, the Clearwing Wasp Moths, without any research.  These Clearwings are wasp mimics, and the larvae are borers.  There are numerous members in this family, and many are very poorly represented with photographs of living specimens.  Pinned specimens from collections are often quite difficult to compare visually with living moths as the colors seem so much duller in museum specimens.  We scoured the pages of BugGuide, eliminating possibility after possibility, until we stumbled upon the Douglas Fir Pitch Moth,
Synanthedon novaroensis, which is represented on BugGuide by a single mounted specimen from Alaska.  Bold Systems Taxonomy supplied additional images of pinned specimens from museums, and it was not until we searched the Moth Photographers Group website that we found a photo of a living specimen that satisfied us that we had properly identified your moth.  We also located this technical paper on the Douglas Fir Pitch Moth.

Douglas Fir Pitch Moth

Letter 2 – Douglas Fir Pitch Moth from Canada

 

Subject: could this also be a scarlet bodied wasp moth
Location: edmonton alberta canada
June 22, 2013 2:02 pm
Hello, I found this guy sitting on the concrete in my back yard in Edmonton Alberta, Canada. These pictures were taken June 22nd 2013 on partially rainy partially sunny days.
Signature: kk

Douglas Fir Pitch Moth
Douglas Fir Pitch Moth

Dear kk,
We believe we have correctly identified your Douglas Fir Pitch Moth,
Synanthedon novaroensis, from the Clearwing family Sesiidae, another group of wasp mimic moths.  You can see one of the few other images of a live specimen on the Moth Photographers Group website.  For more information, see this online article.

Douglas Fir Pitch Moth
Douglas Fir Pitch Moth

Authors

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  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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