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September
7, 2006
Hortiscope
Ronald C.
Smith, Horticulturist
NDSU Extension Service
Q: We seem to have
a terrible epidemic of worms in our yard. How often can Sevin be applied?
We believe that it will take at least a couple of applications. We decided
not to water the lawn this summer. Will this help us get rid of the worms?
Thank you for your help. (e-mail reference)
A: Hot and dry soil
will do a number on the earthworm population. The grub application of
Sevin also will control them somewhat. The applications should be made
during a two- to three- year period. For effective control, do the application
in the spring or fall.
Q: We have sugar maples
along our driveway. Last week, one of them started losing its leaves.
We can’t find any bugs. Do we cut down the tree to make sure we
save the other trees or wait and see what will happen? (Barney, N.D.)
A: I wouldn't cut
the tree down because it may have shed its leaves as a reaction or protection
against the heat and drought. If the branches still are supple and the
cambium is green under the bark on those branches, then that is what
happened. The tree will leaf out again this year or wait until next
spring.
Q: Has ash borer been
discovered in North Dakota? If not, how close is it? I am questioning
whether I am seeing it in a couple of ash trees at my parent’s farm.
The leaves are covered with orange spots. If you look closely, the spots
appear to be something blooming on the leaf. What do you think this is?
Also, I have some cantaloupe plants that were started in a greenhouse
at the beginning of May. Should I be seeing fruit development? All I see
is bloom. Is there a way to attract pollinators? (Jud, N.D.)
A: The emerald ash
borer has not been reported in North Dakota, but it is in Michigan and
Wisconsin. Those states are doing their best to eradicate and quarantine
the areas where they know it exists. In the meantime, we have the lilac
ash borer that is active in our area. Also, there are a host of bark
beetles that are causing problems. If the efforts to contain the emerald
ash borer continue, it is estimated that it will not arrive in our area
for another 10 years. Hopefully, by then, there should be some other
effective control, other than simply cutting down the infested trees.
The leaves on your trees are showing ash rust. Don’t worry about
it at this time, but clean up the fallen leaves this fall. Spray the
tree with Bordeaux or Funginex next spring as the leaves unfold and
again 10 days later. There should be some fruit on your cantaloupe plants.
If not, the vine might be producing only male flowers or it may be a
lack of bee activity. Planting borage will attract bees and will pollinate
the squash flowers as well.
Q: I have thousands
of tiny, white gnats flying around my tomatoes and other plants when I
water. I used a Black Flag bomb, but it didn’t work. It doesn't
appear that they are bothering anything, but I have noticed that my tomatoes
are not setting fruit. What should I do? Thanks for all the info you have
been sending everyone’s way. (Valley City, N.D.)
A: This is a white
fly infestation, which is somewhat unusual for outdoor tomatoes. They
are a curse in greenhouse plantings because they can reduce quantity
and quality. Generally, white flies are controlled by predator wasps
in commercial operations. For homeowners, the best bet is to get yellow,
sticky cards and place them around the plants that are infested. Replace
the cards once they become full of this pest. You also can follow an
aggressive pattern of spraying with insecticides, such as Sevin, when
you see them flying. The egg masses and immature nymphs will not be
affected by the spray for the most part. As Calvin Coolidge once said,
"persistence and determination alone are omnipotent."
Q: We seeded our lawn
in June and now have nice grass, but we also have a lot of weeds and crab
grass. When can we use weed and feed? We have used a starter fertilizer.
When would you recommend applying weed killer and fertilizer? (Ottertail,
Minn.)
A: The best time
is the middle of September because the weather is cooler. Weeds are
a common occurrence in newly-seeded lawns.
Q: I had a lady call
me about white or yellow butterflies in her garden. What can she use to
get rid of them? She has tried garden powders, but they didn’t work.
(e-mail reference)
A: The butterflies
are laying eggs on the cabbage, broccoli, cauliflower and brussels sprouts.
BT (Bacillus thuringiensis) sprays are effective at selectively controlling
caterpillars. Sevin also can be used as a spray on the cabbage crop.
If quick enough, she also can take the butterflies out of the air. This
species is so aggressive at attacking the brassaia family that it becomes
very discouraging to attempt to grow any without getting into a lot
of insecticide use. Nasturtiums and old-fashioned marigolds are supposed
to disguise the scent characteristic of this family, but to date, I
have not had any success with this approach.
Q: We have a large
garden with evergreens around the perimeter. We shrunk the garden to allow
for a buffer zone between the trees and garden. The roots of the trees
have started to grow into the garden, which is reducing plant production.
We dug around the perimeter of the garden and broke off the tree roots,
but they keep growing back. A friend suggested we use copper sulfate at
the edge of the garden to discourage the trees from rooting. Is this an
appropriate use for copper sulfate? Will it harm our garden plants? Do
you have any suggestions for a better solution? (e-mail reference)
A: Tree roots know
a good thing when they find it, so they will keep coming back for the
good aeration, water and nutrients in the garden. Your friend is almost
right in saying that copper screening would do the job. A product called
BioBarrier will keep the roots at bay, supposedly for more than a decade.
Straight copper sulfate might migrate to the garden plants. While copper
and sulfur are essential plant nutrients, the dose would be toxic to
your garden plants.
Q: We have an infestation
of slugs in the roots of our peonies. The slugs now are moving to our
rhubarb plants. The rhubarb plants are very old and have survived without
problems until this year. The slugs seem to be feeding only on the roots.
We dug up one peony and got rid of the slugs. The plant seems to be growing
again. What can we use to get rid of the slugs? Is there something we
can use that will allow us to use the rhubarb? (Gary, Minn.)
A: I have to admit
that this is the first time I've heard of slugs feeding on rhubarb roots.
You can try slug pellets or place shallow trays of cheap beer around
the plant. The beer will attract the slugs. They will crawl in the trays
and drown. You can sprinkle diatomaceous earth around the rhubarb plant
as well. This will lacerate their soft bodies and cause them to desiccate.
Q: I helped a friend
move his hoya plant a few years ago. During the move, a 6-inch segment
of the stem broke off. After many months in water, the stem finally grew
roots, which I then planted in succulent soil. It has grown many leaves,
but has not elongated. At one time, it started to, but then died. Is there
anything I can do to get the end of the stem active again? (Mandan, N.D.)
A: Nip it back to
some fresh tissue to see if that stimulates growth. I don't know if
it will work, but it is the only suggestion I have.
Q: Is there a yellow
fruited chokecherry? If so, it must be rare or have I been missing something?
(e-mail reference)
A: Yes, but as you
say, it isn't very common. The fruit is treated the same for pie and
wine purposes. For the record, this is probably a boughen's yellow cultivar.
Q: As a North Dakota
resident living in the Turtle Mountains, what chance do I have of growing
one or more varieties of Japanese cherry trees? According to National
Geographic's "Field Guide to Trees," they are hardy to zone
4. I understand the trees thrive in the Pacific Northwest. With the substantial
snow cover we receive, I thought that maybe, just maybe, I might have
some success. Also, do you have some information about Tibetan cherries?
I greatly appreciate your time and any advice you may have (certainly
nothing wrong with a flowering crabapple, I guess.) (e-mail reference)
A: As you say, maybe
it will survive and produce flowers for you. It depends on how much
of a challenge you like. As you say, there are lots of flowering crabs
that establish much easier and are every bit as attractive.
Q: My young autumn
blaze maples have leaves with dead, dry tips. The problem mostly is confined
to the mid to lower branches. Are they lacking something? I use a sprinkler
system to water them. Also, after spraying my silver maples with Malathion,
the cottony cushion white sacs are still there and look active. The Malathion
was applied using a canister on a garden hose. Would this have diluted
it too much? I have received your advice to use Sevin or Bayer Advanced.
(e-mail reference)
A: The sacs will
change very little, if at all. It is the crawler that is about the size
of a period at the end of a sentence that you are attempting to eliminate
or reduce in number. It would be better to apply Bayer Advanced in the
early spring, rather than now. Your autumn blaze maples may be getting
too much watering.
Q: I need some help
with my black walnut tree. Four years ago, I planted it in memory of a
dear friend. It always leafs out in the spring and has nice, healthy foliage.
In a month or less, the leaves start getting brown spots, turn brittle
and then die. I have tried different fungicides and herbicides, but nothing
helps. Should I dig it up and start over? I really don't want to lose
it, but it doesn't seem to be healthy. Also, it hasn’t grown much.
(Pingree, N.D.)
A: It is behaving
like an Ohio buckeye and not a walnut. I don't know why it is doing
this, so I suggest that you take it out and start over. Make sure it’s
planted at the right depth. Walnuts do not transplant easily, so you
are better off starting over with a seed or seedling.
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Source: Ron
Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu
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