Re: Mistletoe in Oak
arborwst@cdsnet.net
Sat, 1 Aug 1998 15:47:55 -0500
As per your request on mistletoe, I have been pruning and treating native oaks in Southern Oregon for 17 years. The area between Medford, Oregon and Redding, California has the worst mistletoe problem I have seen anywhere in the world.
The following are my observations:
1. Generally speaking, mistletoe is a secondary symptom of primary stress. Soil compaction (i.e. livestock), drought, roots damaged by trenching activities or backfill, and excessive watering tend to set up a tree for the onslaught of mistletoe infestations.
2. In the past, the use of sprouting inhibitors (such as "Maintain-A"), proved to be highly effective in curtailing regrowth of removed mistletoe, even on the trunk and major branches. Unfortunately, this product is no longer available (due to the prohibitive costs of retesting per new government regulations).
3. I am currently experimenting with the use of asphalt based tree trunk wrap. Although current research has shown that such wraps are inappropriate for use as a trunk guard, I feel that it is the lesser of two evils when addressing the control of mistletoe. The wrap blends in well, and would not overheat the cambium the way black plastic might in our hot climate.
4. The use of tree paints, and white latex reflective paints have proven futile in the long run.
5. In a personal conversation I had with Dr. Alex Shigo, he suggested that I try experimenting with the application of lanolin on the bark, at the point of removal.
6. It has been our experience in this climate, that the use of Florel was cost prohibitive and required a window of opportunity in the air temperature and growth stage of the tree that was extremely difficult to obtain.
7. Extreme cold, either through natural weather conditions, or the use of aerosol compressed coolant (such as is used on sprained muscles at athletic events), sprayed on the fronds may serve to provide some control.
It is my hope that a biotech company might be able to engineer an agent that would be counterproductive to mistletoe.
Genetic predisposition in the tree, pruning and mulch therapies, and adequate watering seem to help inhibit the advent of
mistletoe infestation. I hope this is of interest and value to you.
If you can afford to experiment at the risk of losing the tree, try "Roundup". The old-timers used to leave a stub of mistletoe stem and paint it with 2-4-D.
For further information you can reference: "The Biology of Mistletoes" - Edited by Malcolm Calder and Peter Bernhardt - School of Botany; University of Melbourne, Victoria (Academic Press)
Philip Frazee
Arbor West Tree Experts - Eagle Point, Oregon