What do you notice about the trees in the photo below?
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| Damage to a forest caused by the Southern pine beetle (Dendroctonus frontalis). Source: Flickr |
The trees in the photo weren't killed by a fire or lack of water. In fact, the trees were killed by beetles that are smaller than a grain of rice. Despite their small size, bark beetles are a large concern across the United States. Bark beetles can kill a tree within a few months, and in the western US, entire forests have been decimated by bark beetles.
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Little beetles, big impact: the Southern pine beetle (D. frontalis) is smaller than a grain of rice.
Source: Wikimedia |
Bark beetles kill trees by consuming the inner bark of the trees, which is crucial to trees' growth and to the transport of nutrients and water throughout the tree. Bark beetles burrow tunnels in the wood, and lay their eggs deep within the tree. Bark beetles do not arrive alone, either - they also bring fungi and bacteria that block the tree from expelling the beetles' eggs, allowing the larvae to hatch and consume their way to the surface of the tree.
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Normally, bark beetles aren't bad in a forest - they help with breaking down weakened, dying, and dead trees, which helps renew a forest. Healthy trees can defend themselves by excreting sap, which can kill or immobilize attacking insects. However, when there is an outbreak of bark beetles, even healthy trees cannot defend themselves against the sheer number of bark beetles, causing widespread damage in a forest and even creating a potential fire hazard due to the large number of dead trees. A forest can contain many different species of bark beetles; different species can be identified by the type of tree infested, and by the tunnel patterns created. And with changing climatic patterns precipitated by human activity, there have been increased observations in the north of bark beetles species that had previously been confined to the south, such as the southern pine beetle, which got us thinking - what kinds of bark beetles are in White Memorial?
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| One of our summer interns, Tatiana, filling the trap with hand sanitizer. Source: K. Sudol |
To determine what types of bark beetles were in White Memorial's forests, we used a setup designed by the University of Florida for people interested in knowing what types of bark beetles were living in their backyards. It was pretty simple and inexpensive - first, we cut a small window in a clean and empty two liter soda bottle. Next, we inverted the soda bottle such that the cap was facing the ground, and then we used twine to tie the bottle to a low-lying branch, twig, or small tree. We then put some hand sanitizer into the cap. The alcohol in the hand sanitizer has two purposes - since alcohol is produced by decaying trees, the alcohol attracted the bark beetles. The alcohol also serves to prevent the beetle from decaying. We left the trap out for three mornings, and then we transferred the hand sanitizer and any beetles inside into a plastic bag before removing the trap.
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| Super easy setup! Source: University of Florida |
Using this trap design, we scaled our project to survey as much of the White Memorial property as possible. Between May 22 and June 23, 2017, we established 12 transects. Each transect consisted of 10 traps in a line that were spaced 10 meters apart. Because different species of beetles may be associated with different species of trees, and because White Memorial has a wide variety of forest types, we set our transects in locations with varying forest types. Out of 120 total traps placed, we collected 102 traps with possible bark beetles. We recently sent these beetles to the University of Florida for identification, and we're eager to know what they find!
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| A map of the 12 transects that we established in White Memorial. Source: Google Earth |
If you're interested in knowing which bark beetles live in your backyard, this setup is really easy and effective. Regardless of whether you're a homeowner curious about your backyard, a classroom teacher trying to teach a science lesson, or field scientists like us, this is a project that is easily done at any scale. Any and all results are helpful in helping identify the different species of bark beetles across the country! The project's website is http://backyardbarkbeetles.
Sources:
- http://www.ct.gov/caes/lib/caes/documents/publications/fact_sheets/forestry_and_horticulture/southern_pine_beetle_in_northeastern_u.s._update.pdf
- https://microbewiki.kenyon.edu/index.php/Bark_Beetles_and_Symbiotic_Fungi
- http://www.dec.ny.gov/docs/lands_forests_pdf/spbactsheet.pdf
- http://learnmoreaboutclimate.colorado.edu/uploads/model-lessons/mountain-pine-beetles/bark-beetles-brochure.pdf
- https://cals.arizona.edu/extension/fh/bb_faq.html#1
- https://www.fs.usda.gov/ccrc/topics/species-distribution
- http://backyardbarkbeetles.
org/
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