First a little about a witches broom.
It is often a tightly clustered, diseased, abnormal growth of multiple branches on a tree or woody shrub.
These growths are caused by different organisms. “Tree pruning” can leave a plant susceptible to causes such as insects, viruses and fungus on trees.
The large clump of mistletoe, shown here to the right, is a good example of a "'broom".
This is what they look like when the winter exposes them high up
in the trees of different species. I've seen many of them in Central Florida. However, they are found throughout the world.
trees are full of leaves, they are barely noticed and you may even think they are bird's nests of some kind.
Another type of witches broom, caused by a tree fungus often appears on Ficus bonsai and landscape Ficus trees as well.
I gave this a lot of thought. I had been growing plants too long to think it was true, but I wondered what would make someone else think so ?
Ficus sap can be toxic to humans. Those who are especially sensitive may suffer small rashes, an itch or welts where the sap touches the skin. Most people are only annoyed by the stickiness of the sap ... but toxic to other plants?
Then I remembered an outbreak of witches broom we had at our 5 acre wholesale bonsai nursery, many years ago.
As it was, they all appeared on Ficus and were all on trees in one area. (They never showed up on Ficus nerifolia).
Our plant inspector removed one of the affected branches and sent it to the Florida Department of Agriculture, Pathology Department.
It was identified as Schaeropsis spp., a fungus on trees.
This tree fungus infects stems easily through wounds (such as bonsai cuts.)
This fungus can even be spread through touching the infected area with your hands and then handling a potential host.
Instead of risking our entire bonsai Ficus pre-bonsai crop, we destroyed all the plants in the infected area. All tools were disinfected.
Without disinfection, Schaeropsis can be spread by using the same tool - going from one spot to another... that is where the myth comes from.
The Ficus sap may assist the spread by sticking to tools, but the sap itself is not "toxic" to other plants. Many trees, in addition to Ficus, can be hosts.
Although not common, galls such as this can be another Ficus bonsai problem.
(Photo courtesy DPI, Florida Department of Agriculture)
It's difficult to diagnose the exact plant fungus or germ, but it's relatively unimportant. The cure is the same.
To rid a Ficus bonsai tree of a witches broom or galls of any kind, carefully prune the infected area well below the gall. Seal the removed branch in a plastic bag and throw it out.
Read about disinfecting your tools between plants or between each usage especially on any infected trees.
Consider wearing disposable gloves and always wash your hands with an antibacterial soap after handling these plant problems.
Some witches brooms appear to be caused by genetic mutations! Unlike 'brooms' caused by living organisms, there is usually only one broom per tree when the cause is a genetic mutation, and they do not spread.
Be sure you know what you're working with!
Also see the page on beneficial critters.
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