Howdy Gardening Enthusiast!
I usually get a lot of questions this time of year to help identify a specific
blooming tree. Some of you may already know what I'm talking about, a rather
feathery leafed specimen similar to the honey locust tree that is covered with
beautiful pom-pom pink to peach colored blooms. It's mostly ladies that love
the look of this tree, and want one in their landscapes. Hopefully, this e-mail
will not only serve to help identify the tree, but keep you from making the
mistake of planting one. Yikes ... did he just say DON'T plant one? Yep, I
don't want you to plant one.
This beautiful, blooming specimen is called the Mimosa tree. While it looks
beautiful now, the rest of the year it's either pathetic looking or overwhelmed
with insects and disease. In Hawaii, the Mimosa is a weed. In Texas, it's
susceptible to borer insects, which can girdle the cambian layer just inside
the bark and kill the tree. Yet, its susceptibility to the Mimosa web worm is
the real reason to avoid a Mimosa. The Mimosa webworm is highly destructive to
honey locust trees. It is the larval stage that feeds on foliage and causes the
damage. When fully grown, larvae are about a half-inch long (12-16mm) and are
gray-brown or sometimes pinkish in color with five narrow white longitudinal
stripes. They spin webs around flowers and leaves, and feed on the foliage
within the protection of the web. The surface of webbed leaves is skeletonized,
causing the leaves to turn brown and die.
Then there's Mimosa wilt, the fungal disease. The classic symptoms are wilting
and yellowing of the foliage. In some cases, the leaves will become dry and
shriveled while remaining green or yellowish for some time. Later, the leaves
fall, and the branch dies. Usually the tree is affected branch-by-branch, and
dies completely within a year of the onset of symptoms.
Another common characteristic of the disease is brown discoloration in the
sapwood, especially the outermost annual ring, caused by gum-filled tissue
cells. This hinders or completely inhibits water movement from the roots to the
aerial portion of the tree. This discoloration can be found in trunks and
branches even before the leaves wilt. During the summer months it is not
uncommon for the bark of infected trees to rupture and exude fermented, frothy
sap. Many insects are readily attracted to this sap. The fungus lives in the
soil and enters the tree through the roots. Dead and dying trees should be cut
down and destroyed to avoid the spread of the disease.
So, do you still want to plant one?
If you already have a Mimosa, you can treat for insects with chemicals like
Malathion or Diazinon, but if you get the wilt, there are no known chemical
controls. If you're still not sure about what kind of tree I'm talking about,
click http://www.io.com/~maddog/pho_mimo.jpg
to see a Mimosa tree in bloom.