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by Rett Davis | |
Gardening Q&A by Rett Davis appears in
Alamance County's daily newspaper, The Burlington Times-News,
every Sunday in the Accent section. Each week's installment is
posted to this
website, beginning with January 1998. Scroll to the bottom of
this page to navigate to other Gardening Q&As. Please contact
Rett via e-mail with questions
or
comments in regard to this column.
Answer:
This is a serious problem that I am afraid is
only going to get worse in the coming years. The Asian Ambrosia
beetle has finally found Alamance county. This insect pest was
first detected in Charleston, S.C. in 1974 in peach trees. Since
then it has slowly spread throughout the southeast. I first ran
into this insect last year and have received several calls last
week. This boring beetle will infest newly transplanted trees,
trees that have been stressed (heavily pruned or topped), and
damaged trees. To make matters worse, they will also attack
seemingly healthy thin barked trees. This includes maples,
cherries, peaches, dogwood, pecan, figs, magnolia, and even
azalea. The sawdust tubes that you see emerging from the trunk
are the result of the female boring into the tree. Infested
trees will soon wilt and may die if the infestation is severe.
Rain and wind will destroy the toothpick size sawdust tubes
leaving only the small entry holes. These beetles are most
active from March through the end of April. Once the trees are
infested the beetle cannot be killed in the tree. Licensed
landscape professionals are advised to spray Astro on tree trunks
to provide protection during this time of the year. Insecticide
choices for homeowners is limited to pyrethroids such as
cyfluthrin. This product is marketed to homeowners as Bayer
Advanced Garden Lawn and Garden Multi-Insect Killer. It is also
sold as Tempo. This insecticide is only sold at a few lawn and
garden stores. This will cause much confusion to both the
homeowner and retailer. At this time there are few registered
chemical alternatives. The old standby such as Lindane and
Dursban have proven ineffective.
Question:
Last year I planted a row of Nellie Stevens
holly as a screen. The plants did very well up until now.
The
leaves are turning yellow and falling off. Addtional fertilizer
and water does not seem to stop it. Why are they dying?
Answer:
They are not dying. In the spring Nellie
Stevens and especially American holly will shed their older
leaves. The leaves will turn yellow and tan and fall to the
ground. Although it looks alarming, it is a naturally occuring
event. To reassure you that the plant is healthy, check the tips
of the branches for new growth. New growth should be visible.
The yellowing leaves will eventually fall. A good downpour of
rain will hasten their fall.
Question:
We live in a new housing development with
what I have been told has bad soil. There is no standing water
to indicate poor drainage but we have lost a lot shrubbery. I
have been told we should have a drainage system put in and bring
in some topsoil before we replant. Do you have any suggestions?
Answer:
By far the number one cause of plant death and
decline is soil related. It is estimated that 75% of all plant
problems are related to an unhealthy root system. I am not
referring to low fertility but to poor soil drainage. Many new
housing developments are put on soils have been regraded, filled,
highly eroded, and would not pass a perk test for a septic
system. Even though there is no standing water on the surface,
the internal drainage is terrible. These soils will often smell
sour, have a blue gray coloration, and will be wet even in a
drought. Conditions like this lead to various root rots and root
suffocation. Drainage systems have little impact on these soils
and the addition of topsoil into the planting hole is useless.
So is the addition of sand and gravel in the hole. Unless you
are willing to build berms of good topsoil for planting you need
to be very selective in what you plant. Avoid all culitvars of
Japanese (Crenata) hollies, azaleas, camellias, rhododendrons,
boxwoods, roses, and most junipers. Plant yaupons, Chinese holly
culitivars (Cornuta), inkberry, clethera, winterberry, and
nandina which can tolerate these soils.
Upcoming 4-H Summer Fun Program
Registration for the 4-H Summer Fun Program will begin at 8 am, Wednesday, May 22 at the Agricultural Building. Fun shop offerings for youth ages 5 and up can be obtained by calling the Extension Office at 570-6740.
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If you have any horticultural questions, please direct them to Rett Davis