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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 sounds like classic injury from flower
thrips. These very small insects will feed on flower buds and
will damage them to the point they won't open. Their damage is
also visible on the edges of the flower petals when the appear to
be torn or brown. Your spray for diseases will do nothing to
control insects. I recommend you add an insecticide such as
Orthene, diazinon, cygon, or cyfluthrin to your mix on a weekly
basis. The very dry weather conditions we are experiencing favor
rapid build up of thrips. These insects are causing damage by
stunting the growth of plants.
Question:
Last year our okra grew great but produced very
few pods compared to previous years. Is there anything we can do
to prevent this from happening again?
Answer:
I have found over the years that the two most
common causes of poor okra production are too much nitrogen
fertilizer and a low pH. At one time 5-10-10 fertilizer was very
common in our area and when that was used in gardens most of our
low nitrogen requiring vegetables faired better. Now many
gardeners use liquid fertilizers such as 20-20-20 and 17-17-17
for just about everything. In the case of okra, when it gets too
much nitrogen it grows into a giant plant with big leaves with
little fruit to pick. In addition many gardeners still forget to
lime the soil adequately and often. Garden soils need to be
limed about every three years with about 50 pounds of lime per
1000 square feet of garden. This year fertilize okra when the
plants are 6 to 8 inches tall with approxiamtely 1/3 of a cup of
10-10-10 fertilizer for every 10 foot of row. Repeat again at
the same rate 3 weeks later. That is all for the season.
Question:
We planted Otto Luken English laurel around
our home as a foundation planting. In the past few weeks we have
noticed the leaves turning bronze in color. What could be wrong
with them?
Answer:
You can thank all this dry weather for the
rapid explosion of the spider mite population. Spider mites are
tiny warm season arthropods (not insects) that insert their tiny,
sissor-like mouthparts into leaves and suck out the contents of
the plant cells. Hot and dry weather accelerates the life cycle
of the spider mites. Horticultural oils (Volck oil, Ultra-Fine
Spray oil) are moderately toxic to mites and are relatively safe
to humans. There is no residual activity with oil so several
sprayings is a must. Three sprayings are often required about 5
days apart to control these pests. Spray the plant thoroughly
especially the underside of the leaves. Commercial nurserymen
can use the insecticide Joust to give excellent control of adult
mites and mite eggs. Avid is now labeled for spider mites
outdoors except on coniferous evergreens. Floramite is another
excellent miticide for greenhouse, nursery, and landscape use.
Question:
The leaves on our river birch are all rolled up
and crinkled. Some are turning yellow and falling to the ground.
Is the tree dying?
Answer:
The spiny witch-hazel gall aphid will cause
bumpy ridges on the leaves of birch. It is really too late in the
season to do anything about this insect pest. This is mostly a
cosmetic problem and few trees are severly harmed. Water newly
planted trees weekly and they will grow out of this early season
damage.
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If you have any horticultural questions, please direct them to Rett Davis