Tree-mendous

Tim Iverson
Seasonal Naturalist
Cunningham Falls State Park

(11/2012) The world of trees may not seem glamorous, but just under the bark is a world of intrigue with dire implications for us all. James Bond may sport all the glitz of a secret agent, but right in our own backyards some of our very own trees are fighting a battle with invasive alien species that reckons millions of dollars worth of destruction to state and local economies. So don’t be fooled, the world of trees is packed with intrigue, and fraught with alien invaders that seek to destroy entire species for their own malicious purpose. Trees come in all shapes, sizes, colors, categories, and each one provides a unique service to the environment and economy.

In broad general terms trees are broken down into two main categories: coniferous and deciduous. Coniferous trees have needles, and produce cones. Deciduous trees have broad leaves, which die off in cooler temperatures in a process called abscission. Deciduous means "to die off", which is where the name comes from and this usually, coincides with winter and cooler temperatures. Abscission happens when leaves stop producing chlorophyll and green pigmentation. Depending on location and weather from mid-September through mid-November the forest lights up with a beautiful array of colors. This allows other pigments that are already present, just unseen, to shine through until the leaf breaks away and floats to the ground.

For some of the best views in the park of the fall foliage try trekking the Cat Rock and Bob’s Hill trails, which are moderate to challenging hikes (respectively). Cat Rock Trail is approximately 3 miles round trip, and can be accessed off Rt. 77, just across from the Catoctin National Park administration building. The Bob’s Hill Trail is approximately 3 miles round trip to the overlook. This trail ascends about 1,100 ft to the top of the mountain, not only ensuring sweeping views of the valley but also a shortness of breath. This view is certainly earned, but remember it’s all down hill on the return, and it’s well worth the investment.

While the transient display of color fades into winter the coniferous trees will remain. Along Hunting Creek, at the base of the falls, and throughout other areas of the park reside Hemlocks. These trees are presently defending themselves from invasive species. The foreign invaders wrecking havoc upon these trees are known as the Hemlock Wooly Adelgid (HWA). The HWA is a tiny insect that measures in at 1/16 of an inch, or about the size of a ball point pen. As a true undercover operative, HWA will infect a hemlock and eat away at the starches and nutrients stored in needles. It hails from Japan, and was first introduced into our park in late 2002. The larger trees became infected with HWA and were killed off within three years. Subsequently, HWA spread to the smaller trees and killed most of the understory. Ranger Eric Creter notes, "Hemlocks are the last defense of the creek bank. They play a vital role in buffering pollution and sediment from running into the creek. Hemlocks also provide shade to creeks, which helps regulate water temperatures". Since the initial infestation and die off the Maryland Park Service, Maryland Forest Service, and Catoctin National Park banded together in alliance to confront the menace.

Beginning in 2007 Maryland Department of Agriculture began treating the remaining trees with stem injections, which looks akin to a medical IV for people. By 2011 Maryland Department of Forestry planted approximately 120 new Hemlocks, which were pretreated for HWA. Currently Cunningham Falls and Catoctin National Park are in the process of planting 200 trees along Hunting Creek with the help of the Maryland Conservation Corps. These trees were funded through a grant paid for by the Odwalla Corporation. Recently while leading a hike to the base of the falls I was explaining this very situation to a group and someone inquisitively pointed out that it looked like one of the Hemlocks was in tree jail. While I can’t promise I maintained my composure I did manage to explain that it was not in fact tree jail. This cage was actually protecting the tree from "browsing" by wildlife. Apparently the deer and other wildlife browse a little too enthusiastically. So while all trees are being treated against future HWA infestation smaller ones are also being surrounded by cages and netting for protection.

At this stage of the game plantings and treatment will continue, with other means of protection being investigated. A treatment for HWA lasts approximately five years. Success of this program and regiment will be monitored overtime to determine the next appropriate course of action. However, Hemlocks are not the only trees in our area who are defending themselves from would-be foe.

The Emerald Ash Borer (EAB) may pose the greatest threat to any species of trees currently. This little green bug, about an inch long, takes no prisoners and doesn’t differentiate between any of the various species of Ash trees. It’s estimated that it has already destroyed 50 – 100 million Ash trees in North America, since its discovery in 2002, and is well on track to devour much of the remaining 7.5 billion. Trees haven’t seen such destruction since the American Chestnut was virtually eradicated from the "Chestnut Blight" at the beginning of the 20th century. In a matter of 40 years the estimated near 4 billion American Chestnut population was decimated, and only several thousand still exist today. Today the Ash tree is staring down a comparable problem.

The EAB seeks out Ash trees and lays eggs in the trunk of the tree. When these eggs hatch they essentially eat their way out, making the tree susceptible to disease. When the larva reaches adult stage they migrate into the canopy of the tree and begin to feast on the leaves. When cold weather returns they will overwinter by boring into the trunk and base of the tree and the process repeats annually. The EAB gives a one-two punch by eating through the bark into the trunk, and the leaves in the canopy. In Maryland the spread of the EAB is being curtailed by banning the moving of firewood, and in state parks you can only burn wood that has been treated for the pest. The ban on moving firewood is effective in the short term, but the EAB is known to migrate at least ½ a mile.

Over the past several years you may have noticed purple triangular boxes hanging from trees. Those boxes are essentially bait traps, because the best defense is a good offense. If there are any of these pests found in a trap then treatment will begin in that area to prevent further spread and destruction. Once the EAB has been detected various insecticides can be deployed to prevent any additional damage. Much research is still underway on how to best handle the problem. Currently Maryland is operating with universities, state, and federal agencies to manage the issue. Treatment and removal are what is being utilized throughout the country, and possible introduction of other species which are predators of the EAB are being considered and experimented with in other areas of the nation.

Sure, trees may not hold the explosive action of a spy vs. spy tale, but some are in grave danger and their importance isn’t just limited to supplying the air we breathe. There is a Greek proverb that reads, "A society grows great when old men plant trees whose shade they know they shall never sit in". We can remember the outcome of the American Chestnut, and look to the Hemlock and Ash trees with promise as we prepare them for their respective battles. Thanks to the many combined efforts of various local, state, national, and civic contributions we can hopefully enjoy the shade of these magnificent trees for generations to come.