Sudden Oak Death - Phytophthora ramorum

Sudden Oak Death (Phytophthora ramorum) - SOD (also known as Phytophthora canker disease), was originally identified in Germany and The Netherlands in the early 1990's on Rhododendrons .  Since being discovered in the United States, it has been confirmed in forests from California, Oregon, Washington and British Columbia.  The origin geographically of Phytophthora ramorum is unknown and before the early 1990's there were no reports in Europe or the United States.  The areas that do exist in Europe and the United States are believe to have been originally transported from other areas or even the original site of origin.  Phytophthora ramorum's very limited distribution related to the host's distribution suggests a more recent introduction versus a point of origin.  

Image Citation: Joseph O'Brien, USDA Forest Service, Bugwood.org

Two types of disease are caused by Phytophthora ramorum, the first being bark cankers and the second being foliar blights.  Bark cankers may eventually kill the host while foliar blights serve as a reservoir for the pathogen to remain within and be tranferred from the foliar host.  The list of hosts (and foliar hosts) seems to grow with each new report and now includes Coast and Canyon Live Oak, Tanoak, California Black Oak, Coast Redwood, Douglas Fir, Rhododendron, Bay Laurel, California Buckeye, Madrone, Bigleaf Maple, Oregon Myrtle, Toyon, Honeysuckle, Arrowwood, Camellia, Californis Hazelnut, Mountain Laurel, Valley Oak, Poison Oak and Grand Fir.  In lab testing it has been found that both Red and Pin Oaks are susceptible this opens up the potential for spread into the Eastern portions of the US as the Red Oak family is found in most of North America. In the field the White Oak family including the Valley, White and Blue Oaks have not been confirmed as hosts or even shown any symptoms- hopefully this means they are immune to Phytophthora ramorum or at least have a higher tolerance level.

Image Citation: Bruce Moltzan, USDA Forest Service, Bugwood.org

As with many diseases of woody plants the spread of Phytophthora ramorum most likely occurs from contact with foliar hosts, infected material, soil transfer and spreading by rainwater.  Windy, cool and moist conditions are also thought to aide in the spread of the pathogen by further dispersing the spores from their foliar hosts.  Transporting (for nursery sale, wholesale or production) of foliar hosts may also aide in the spread of this disease making it harder to control.  

The symptoms of Sudden Oak Death are easily identified by large cankers on the trunk or main stem, browning of the leaves or even death of the entire plant/tree.  Some infected trees also become host to Bark or Ambrosia Beetles, or Sapwood rotting fungus-these outside organisms may speed up or even contribute to the death of the host.  Foliar host infection os harder to identify and may not be noticed until it is to late.  With a foliar host you may notice deep gray or brown lesions on the leaf blades, vascular tissues, petiole, or stems of the host.

Learn more about Oak trees and their diseases/pests on our Website www.ArundelTreeService.com  or our blog  www.MeetaTree.com 

What is Oak Wilt?

Oak wilt effects all Oak species, but has different results and signs with each group. Ceratocystis fagacearum is the fungal pathogen that causes Oak Wilt.  It is a vascular disease, meaning the fungus is only found in the outermost xylem of the tree. This fungus is thought to be native of the Eastern US but the problems identifying and isolating it delayed the recognition of the true effects of the fungus until the 1980's.  Oak wilt is a very aggressive disease, currently it is one of the most serious tree related diseases in the Eastern US-killing thousands of Oaks each year in both forest and landscape settings.

Oaks in the Red Oak family- such as Black, Northern Red, Northern Pin and others with pointed edged leaves are particularly susceptible and when infected usually die over the course of a single season-some declining to the point of complete defoliation in a matter of weeks.  Infected Red Oaks will begin wilting from the top of the tree down, the leaves will gradually become bronze in color and fall off of the tree.

Oaks in the White Oak family- such as White, Swamp, Bur, or others with rounded edged leaves are less susceptible to Oak wilt and when infected can live for several years, losing only a few branches each season also from the top down.  Symptoms in White Oaks are very similar to that of the Red Oaks.








The Live Oak however is not so predictable, it's infection level and timeline is effected by many other variables in the environment.  Usually however, Live Oaks infected will die within a six month period from the first sign of decline.  Lives Oaks foliar symptoms differ from those of the Red and White Oak.  An infected Live Oaks leaves will develop chlorotic veins that eventually turn necrotic prior to falling from the tree.

Oak Wilt fungus spreads in two basic ways.  Spores can be transferred from an infected tree to a healthy tree by insect movement or The fungus can move from the roots of an infected tree to those of a healthy tree through root grafts.

Oak Wilt is very similar to Dutch Elm disease but considered to be more controllable.   On good factor to consider is the nitidulid Beetles that carry the Oak Wilt Fungus do not have chewing mouth parts, so in turn would need another creature or a damaged portion of the tree to make the transfer.  This is different from the Beetles that carried Dutch Elm disease, they do have chewing mouth parts and are able to enter any tree without help.

When an Oak has died from Oak Wilt, trees should be chipped and then burned or covered with plastic sheeting to speed composting.  The heat from the chips composting should destroy or severely enervate the fungus.  Logs from infected trees should never be moved to unaffected areas, even for use as firewood.

More at www.ArundelTreeService.com or www.MeetATree.com


Downloadable Oak Wilt fact sheets: 

http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsbdev2_043443.pdf

http://na.fs.fed.us/pubs/howtos/ht_oakwilt/identify_prevent_and_control_oak_wilt_print.pdf


Photos sources:
Joseph O'Brien, USDA Forest Service, bugwood.org (Photos# 1,3,4,6 & 7)
Forestthreats.org with Google Earth overlay (Photo #2)
Wikipedia (Photo #5)

Meet A Tree: Devil's Walking Stick -Aralia spinos

Meet A Tree: Devil's Walking Stick -Aralia spinos: The Devil's Walking Stick - Aralia spinosa  is best known for it's prickly trunk, umbrella form, and bi-pinnate or tri-pinnate leav...

Meet the Tent Caterpillars

It is that time of year again where those mysterious little tents seem to form in our trees overnight.  Have you ever wondered what they are and what they are doing in there?

Tent Caterpillars (Malacosoma) are a mid sized genus in the Moth (Lasiocampidae) family.  There are species found in both North America and Eurasia.  There are thought to be 26 different species (some having many subspecies), 6 of which occur in North America.  They are considered by many to be pest as they have a nasty habit of defoliating trees.  Tent caterpillars are considered to be one of the most social of all caterpillars often developing together within the same tent system. They are not only social but most often very colorful and are easily recognized by their silk tents built within the branches of host trees.  Tent mates are often decided based on the foraging ability of each caterpillar.  The Eastern Tent Caterpillar is the most common of the genus.  Tent caterpillars hatch from their eggs in the early spring at the time the leaves of their host trees are just unfolding.

Image Citation: Robert L. Anderson, USDA Forest Service, Bugwood.org

Some species of Tent Caterpillar build one large tent that houses them throughout the larval stages, while others build a series of smaller tents that are abandoned sequentially throughout the stages.  Tent caterpillars establish their tents soon after they eclose. They always make their tents within the nodes and branches of trees in a location that catches the rays of the morning sun.  Positioning of each tent is very critical as the caterpillar must bask in the sun during the early morning hours to elevate their body temperatures.  If their body temperatures dip below 59 degrees farenheit their bodies are not able to perform the simply process of digestion.  Each tent is made up of layers of silk that are separated by gaps, each individual compartment temperature can vary noticeably.  The caterpillar can move between compartments to alter it's body temperature as needed. 

Image Citation: Lacy L. Hyche, Auburn University, Bugwood.org

Tent Caterpillars are foragers searching out food and feeding to the point of repletion, once it has reached that level it returns to it's tent.  Along the way each caterpillar leaves a trail for other tent mates to follow to a good food source.  The chemical trail left behind in often compared to that of the ant or termite.  Their development is greatly in tune with that of their host trees, once the leaves of the host tree reach maturity they are no longer to feed from them.  They feed multiple times a day based on the needs of that level of the larval development.  They often leave the tent in mass, and move together to feeding sites.  

Image Citation: Lacy L. Hyche, Auburn University, Bugwood.org

Caterpillars grow at a very rapid pace and complete their entire larval process in a short 6-8 week period.  Once they leave their tents they find a suitable location (often a protected area on the ground or a structure) to spin their cocoons.  About two weeks after spinning their cocoons they emerge as adults moths.  Shortly after this point the female moth excretes a pheromone attracting a male to her for the purpose of mating.  After mating the eggs are then placed around branches and covered with spumaline, this material prevents the eggs from drying and protects them from parasites.  Once the eggs are laid the female dies.  The cycle of a female moths adult life may only last a short 24 hours while a male can live for a week or more.  Within three weeks of egg laying, small larvae can be identified within each egg mass, these larvae will remain encased within their shells until the following Spring.

Meet more trees and pests on our website www.ArundelTreeService.com  or follow our blog  www.MeetATree.com

Salvaging your trees and shrubs after heavy snow or ice

With what forecasters are calling a possible snow storm of the century just hours from arriving it is a little too late to take those extra steps to prevent possible storm damage to your trees and shrubs.  You can however be prepared for how to handle certain situations that may arise after the storm has passed.  The first thing to remember is DO NOT try to swat, beat, bang or knock heavy snow or ice off of your trees or shrubs.   They may be leaning over or look like they are going to break at any moment but you interefering with Mother Natures "process" will more then likely cause more harm then good, not to mention the risk you take of injuring yourself if the tree should give way and fall on you.....or cause the snow and ice load to fall on you..... It is just not smart either way you look at it so PLEASE don't try it!  In cases of small evergreens (Yews, Junipers, Hemlocks, Leylands, etc) and snow (not ice) you can gently brush snow off ot the limbs with a soft broom to help eliminate some of the weight from its branches, again please wait until after the storm has passed.

Image Citation: Amy Gilliss, Arundel Tree Service

If your trees are damaged remember, trunks, limbs and branches can in some cases be cabled or braced professionally (if the damage is not to severe).  If the damage is too much for cabling or bracing to correct, damaged sections may be able to be cut back to a safe point to save the remaining tree.   In cases of severe damage the entire tree may need to be removed entirely and replaced with a more sturdy option (Remember the right tree right place rule if you are replanting!).  When trying to determine if a tree is worth saving you need to considered not only the extent of the damage but the extent of the possible repairs and the overall value of the tree itself.  If your tree has a small amount of bark that is peeling, ripped or torn after a limb breaks off completely, do not try to cover the wound or repair it.  If it is hanging and pulling on the wound causing further damage, you can cut (with clean sharp trimmers) off just the loose/hanging portion, leaving a small portion loose near the edge of the wound (not cutting tight to the wound) be very careful not to pull or peel anything further from the tree. Trees have a natural process (CODIT) by which they heal themselves.  Covering wounds or interfering during the process could actually prevent this healing process from occurring.

Image Citation: Billy Humphries, Forest Resource Consultants, Inc., Bugwood.org

If your small tree or shrub begins to uproot it may be able to be uprighted and secured with stakes or guy wires.  Keep in mind that if more then 1/3 of the roots are damaged you may be fighting a losing battle.  Do not try to upright large trees, not with your truck, not with a come-along, and never with a ladder (yes we have seen the results of these attempts ad they are not pretty) - if the tree is too large to be lifted by natural human power then contact a professional and let them lead you in the right direction.  

Image Citation: Joseph O'Brien, USDA Forest Service, Bugwood.org

Some tree varieties are damaged more often during storms then others because of inherent structural weakness such as weak wood, weak roots or narrow crotch angles, these include but are not limited to Bradford, Cleveland and Aristocrat Pears, Elms, Poplars, Silver Maples and many common evergreens/conifers.  With these types of trees artificial support may be recommended to help prevent crotch or branch splitting or breakage. Of course, it is always best to plan ahead before storms arrive, look up at your trees often to monitor for any changes that may be cause for concern. Remember, trees are living, growing and changing, they require care maintenance and TLC to thrive!  Structural damage caused by wind and ice can usually be prevented by careful and through pruning including removing weak/diseased limbs, or limbs forming narrow crotches.  

You may reach us during an emergency (24/7/365) via email arundeltree@gmail.com or call our office during regular business hours (410)439-1900.  Stay safe if you must venture out during the storm, otherwise stay warm and enjoy the Snow Days to come!

You can always keep busy by reading our blog www.MeetaTree.com or exploring our website for more tree facts and tips!www.ArundelTreeService.com