Posts Tagged ‘infections’

Oak wilt is caused by a fungus (Ceratocystis fagacearum) which colonizes the vascular system of the tree.  Conduction of water is disrupted causing the leaves to wilt and ultimately for the tree to die.  The disease is highly virulent and spreads in two (2) known ways.  Trees which have formed root grafts with infected trees may themselves become infected through root graft transmission.  For this reason entire stands of Oak forests may be destroyed over a period of time.  New Oak wilt infection centers may begin when a small sap feeding beetle (aka Nitidulid) visits a spore mat on an infected Red Oak.  (Live Oaks do not produce spore mats).  Once the insect has visited a spore mat, his body may carry the fungal spores to a fresh wound, thus creating a new Oak wilt center infection.  The sap feeding beetles are attracted to feed on the sap which oozes from fresh wounds on trees.  Sap feeding beetle activity, spore formation and tree susceptibility are all at high levels from February to June.  For these reasons the Oak wilt control strategy involves the following recommendations:

1. Avoid pruning mid February – mid June (Red Oaks and Live Oaks).
2. If you must prune during this time, paint cuts and wounds as soon as possible after they occur.  The sap flow from wounds usually has stopped within 24-48 hours, therefore, old wounds do not require painting.
3. Healthy trees near Oak wilt infection centers may be treated on a preventable basis with the fungicide “Propaconizol” (aka Alamo).  This fungicide is injected into the tree at the root flares, and can protect trees for up to three (3) years.
4. Once trees have become infected, successful therapeutic treatment with Alamo is possible, however, results vary and most trees will not survive once symptoms develop.
5. Infected trees, particularly Red Oaks, should be removed promptly.  Red Oak firewood may be another means by which the fungus may be transported to new areas.

Additional research is needed to solve the biology regarding the overland transmission of this potentially devastating tree disease.

More information is available concerning Oak wilt through the Texas A&M extension service, the Texas Forest Service

If you have any further questions or suspect you may have Oak wilt please give us a call or fill out a QUICK contact form!

Winter is upon us and many times our trees go without attention.  The dormant season is actually a very good time to prune many of our shade and ornamental trees.  One of the most obvious things we deal with this time of year is mistletoe.

This plant is a parasite that derives its nutrients and moisture from the tree it has infected.  Infections left to develop in trees can lead to weakened areas in larger limbs thus resulting in limb failure.  Once the mistletoe plant matures, seeds are produced which spread throughout the tree canopy, causing multiple infection sites.  Our mistletoe control program is directed toward removing entire branches or twigs infected with mistletoe.  When large limbs or limbs critical to the structure of the tree are infected we remove the mistletoe only, however regrowth occurs.  Mistletoe removal will be necessary about ever 2 to 3 years on average.  This will address regrowth of old infections as well as new infections that will constantly occur on susceptible species.

The North Texas area has a number of susceptible species, many of which are growing in our residential landscapes.  Cedar Elm by far is the most susceptible high value species where we see mistletoe infections.  Other species include American Elm, Hackberry, Mulberry, Ash, and Bois d’ arc.  Winter is also a common time for new infections to occur as birds will consume the fruit that has now matured, and deposit seeds throughout the canopies of susceptible species.  We can remove mistletoe anytime of the year.  However, it is much more visible during the dormant season and in most cases more easily removed this time of year.

Another important process that can be forgotten this time of year is deep root fertilization.  Our process utilizes a high quality organic fertilizer solution applied directly to the root area of our urban shade trees.  This material will be available for uptake by the tree or plant for 6-8 months.  Many of us forget our southern soils rarely, if ever, freeze and soil temperatures are generally quite favorable for root growth and development this time of year.  The mixture we use is applied under pressure which aids in aeration of the root zone as well as uniform distribution throughout the root area of our trees.  Many times the lack of oxygen alone can be the most limiting element in healthy root growth.  This is especially true in the heavy clay soils of North Texas.

Call one of our qualified I.S.A. Certified Arborists to assist you with a plan and an estimate of cost for mistletoe removal and/or deep root fertilization.