Ask
the ‘Carefree’ Gardener
by
Craig Allison
Dear
Craig:
I
caught the last part of your radio show on
KFNX 1100 one Sunday morning. You had a guest
on and were talking about a kind of insect
that could destroy oleanders, citrus and grapes.
I have a beautiful oleander hedge that surrounds
my property. I would hate to lose it and the
privacy it provides. Can you give me more
information about this?
Lesa
in Phoenix
Dear
Lesa:
Thank
you for listening to our show. We are pleased
to help all those who call from throughout
the country. On July 9, we had Dave Maddison,
the Quarantine and Nursery Program Manager
with the Arizona Department of Agriculture,
on the Carefree Gardener radio hour. He was
talking about a possible threat to not only
oleanders, but also to grapes grown in Arizona.
The culprit is called the Glassy‑winged
Sharpshooter, or GWSS for short. It is an
insect about one‑half inch in length,
dark brown to black in color with small ivory
or yellow spots
on
its head and transparent front wings. GWSS
feeds on an assortment of host plants, including
oleanders and grape vines. Damage isn’t caused
directly from the insect, but from the diseases
it can spread from plant to plant. Once the
GWSS acquires the bacterium from infected
plants, it will remain in its system for the
life of the insect, approximately six months,
and can be transmitted to each plant it feeds
on.
The
threat to oleanders is from the spread of
oleander leaf scorch. This is a lethal disease
that can kill
shrubs within two years of infestation. The
leaves start to yellow and the edges and tips
begin to look scorched. The death of twigs
and branches follows.
Unfortunately,
there is no cure for oleander leaf scorch.
Grapes
are also at risk from a disease called Pierce’s
Disease. You may be surprised to learn that
grapes can and do grow well in the Southwest.
When I lived in Phoenix, I had an arbor covered
with grape vines to shade an area behind my
pool. Many edible and wine grapes do well
here, and there are about thirteen active
wineries in Arizona, most located in the southeastern
part of the state. As with the oleander leaf
scorch problem, there is no cure for Pierce’s
Disease.
