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August
3, 2006
Hortiscope
Ronald C.
Smith, Horticulturist
NDSU Extension Service
Q: We need to move
a large, beautiful lilac bush. When is the best time to relocate the bush?
What's the best method? (e-mail reference)
A: The best time
is early spring while the bush is dormant. The next best time is in
the fall after the leaves have dropped. The worst time is now. If the
shrub is accessible, a small-scale tree spade probably would do the
best job because it would be able to encompass the largest mass of roots
for moving. Otherwise, it would be too big to be moved by hand because
too much of the root system would have to be left behind.
Q: My young maple
tree is losing leaves (many) and I just noticed that the branches seem
to be turning black. I am not sure what variety it is, but the leaves
are green. They seem to be healthy leaves (not brown) when they fall off.
I would like to save it because I planted it in memory of my son, who
passed away. Until this spring, it has grown very well and has been healthy.
(e-mail reference)
A: This could be
what is known as sooty mold, a secondary pathogen that results from
aphid- feeding activity. Carefully examine for aphids on the underside
of the leaves and the small, new growth. Aphids excrete a sticky substance
known as honeydew that causes this mold to grow under the right conditions.
Control the aphids and the mold should disappear. If not, then a fungicide
application will clear it up.
Q: We purchased a
30-year-old home two years ago. There is a wonderful weeping birch that
I assume was planted shortly after the house was built. I have noticed
that there are a lot of dead branches. What can I do to ensure that we
have this majestic tree with us for many years to come? (e-mail reference)
A: Get in touch
with an International Society of Arboriculture-certified arborist to
trim the dead branches. The tree is probably under attack by bronze
birch borers, which if allowed to go unchecked, will kill the tree at
some point. The tree also should receive an injection of a potent insecticide
that will translocate through the transpiration stream and kill actively
feeding larvae. Additionally, the tree should be fertilized almost every
year and kept watered to increase its vigor. This will make the tree
less attractive to the borer.
Q: I am having problems
with my vegetable garden. The peas came up nicely, but it didn’t
take long for the leaves to start curling. I dug some up and found rotten
roots that were brownish and soft. What would cause that? I also am having
problems with my cucumbers. They also came up nicely, but then the leaves
started curling. They haven’t died, but aren’t growing. These
plants also have rotting roots. We are very dry here, but I try to water
once a week. The only thing I have done differently is that last fall
I put a load of manure on that spot in the garden. This spring, I took
most of it to other gardens, so there wasn’t much left when I tilled
it. There are self-seeding flowers coming up in the same spots as the
cucumbers and peas, but the flowers look fine. Any ideas what could be
wrong? (e-mail reference)
A: The manure brought
too much salt to the soil. The salt is killing the seedlings and transplants.
The flowers that are volunteering are tolerant to high salt levels.
With copious watering, the salts should decrease during this growing
season. You successfully should be able to plant a garden next spring.
Q: I have a 27-year-old
linden tree that is sick. The leaves are pale green and small. It appears
to have some black substance on the bark. It was like this last year,
but not as bad. Can it be saved? Thanks! (Oakes, N.D.)
A: The tree has
an aphid or cottony cushion scale problem. Carefully check the leaves
or get an ISA-certified arborist to check the tree and make recommendations.
Only an on-site visit or possibly a sample sent to our Plant Diagnostic
Lab in Waldron Hall on the NDSU campus in Fargo could give you a positive
determination. Address the sample to Kasia Kinzer at the above location.
The zip code is 58105. Send it dry in a plastic bag at the beginning
of the week. That way it won’t sit in the post office during the
weekend.
Q: I bought a large
bag of Miracle-Gro potting soil. I used about one-fourth of it and then
stored the rest in a watertight container. I went to get it to add to
some soil for tomato plants, but the Miracle-Gro was full of black ants.
Will it hurt the tomato plants? (e-mail reference)
A: I never have
known ants to hurt tomato plants, so I would go ahead and use it. The
ants will settle into the surrounding environment or be preyed upon
by the local population, so you should have nothing to worry about.
Q: We have an old
apple tree that we built a deck around. There is sawdust all over the
deck on a daily basis. Yellow leaves are dropping and the main trunk and
branches have bark that is curling and peeling off. We haven't done much
to the tree in the eight years we’ve lived here. We love the tree
and will do anything to save it. (e-mail reference)
A: It sounds like
borer or bark beetle activity that is slowly killing the tree. It should
be evident where the sawdust is coming from. Once they invade the tree,
they are very difficult to control. If the borer or bark beetle activity
can be located and the branches that are infested removed, that is the
best immediate control. After that, spray the rest of the tree with
an insecticide known as Lindane. It is toxic to borers who try to reinfest
the tree and has long residual activity. If you do spray, do not eat
the apples from the tree this year.
Q: I inherited a grapevine
that I assumed was wild, but who knows. In the spring, I get tiny grape
clusters, but they disappear in a few weeks. It's like they burst into
flower and then they're done. Is there anything I can do to get fruit?
(e-mail reference)
A: You may be seeing
the flower buds, but not the fruit. If the flowers were not fertilized,
they will not produce fruit. You may have one of those all-male vines
that do not produce female flowers or vice versa. Most grapevines are
hermaphroditic, which means both sex organs are present ("perfect
flower"). The vines are wind-pollinated, so with no other vine
in the area, you won’t get fruit set.
Q: We have a producer
who has slime mold in his grass. He wants to know if he can spray it with
anything. (e-mail reference)
A: Anything that
can be sprayed to control the problem would impact the grass as well.
The best bet is to core aerate, follow up with a power raking and try
not to water a lot. Also, tell the producer to cut in half whatever
he/she is doing.
Q: We have large,
white patches in our lawn. The problem seems to be where there is shade
for part of the day. Is this a disease or fungus that has to be taken
care of or do we just let it go and call it weather-related. Any help
you could give would be greatly appreciated. I also have had cucumber
and bean plants die. The plants dry up and look like they rot off or were
chewed off, but it is hard to tell. I put Sevin on them, but I don't know
if that will help. Thank you. (Oakes, N.D.)
A: It is probably
powdery mildew arriving early because of the high humidity and dew points
in your area. The grass should outgrow it with a little encouragement
from a light application of fertilizer and collecting the grass clippings
when mowing. It is not lethal to the grass plants. As for the vegetables,
it could be any number of diseases because it is hitting different crops.
Sevin is an insecticide, so it will not control the problem. Try to
find a fungicide appropriate for vegetables, such as Funginex, which
should be available at just about any garden store.
Q: We have a terrible
problem with blossom end rot, but only on our zucchini. The tomatoes and
cucumbers are fine. Any ideas? (e-mail reference)
A: Harvest the zucchini,
cut off the degraded end and consume the rest. Avoid vigorous cultivation
and wide swings in irrigation cycles. As with some tomato cultivars,
blossom end rot usually is limited to the first fruit set. Later fruits
are usually free of the disease.
Q: My gloxinia bulbs
(purchased a few months ago) were planted in pots that seemed too deep
for the bulbs. After growing a few small leaves, the stalks suddenly fell,
went brown and wilted. I assumed it was a fungus, so I dug the bulbs out
and saw that all the roots were rotten. I cut the bulbs to see if I could
save any part of the bulbs. To my surprise, the inner color of the bulb
was dark brown. Is this the right color? Also, how can I tell if my other
gloxinias are having root rot or are starting to go into a rest period?
I may have overwatered them. Thank you very much for your valuable help!
(e-mail reference)
A: Having never
cut a gloxinia tuber in half, I honestly cannot say if this is the color
they are supposed to be. My guess would be no because the roots had
rotted. As to the rest period versus root rot, if you have the tuber
in the right soil mix and pot, keeping the media just moist during the
flowering period should not lead to root rot. Once past the flowering
period, allow the plant to "die down" by withholding water
as would happen in the plant’s natural setting in the tropics.
This should last about six or more weeks. Then slightly moisten the
media and continue to do so until new growth is observed.
Q: I live in central
South Dakota. We are in a very dry area and are seeing a lot of spider
mites on our spruce and cedar trees. What can we do before there is some
damage to our trees? Some are large, older trees and some are newly planted.
I know that a good rain would do the trick, but don’t think it will
happen in the near future. Is there a chemical that I can use, such as
malathion? (e-mail reference)
A: If you can, hit
the trees with a hard spray of water from a garden hose or a pressure
sprayer. If you have a family member who belongs to the volunteer fire
department, get the tank truck and use that to blast the mites. I used
to be a volunteer fireman and used the tanker for such purposes. Of
course, that assumes there was no fire that needed putting out! Orthene
is an insecticide that will provide some mite control, but entomologists
tell me that using any chemicals to control them results in a resistance
buildup that takes place quite quickly. With water, that doesn't happen.
Q: I purchased variegated
ivies that had a nice blue-green hue to them, but after they started to
grow at home, they turned a regular green. Is there anything I can do
to keep it the bluish-green hue? One more variegated question: I have
an old hosta given to me by my grandmother some 30 years ago. In the spring,
it comes up green with a variegated leaf, but then the variegated leaf
turns green. Is there anything I can do to keep the variegation? (e-mail
reference)
A: Variegated plants
can be fertilized in the same fashion as other plants of the same species.
You might ask the nursery what its trick is to produce the blue-green
hue that you like. As to the hosta turning from a variegated to a full
green, I have no idea other than it is the characteristic of this particular
cultivar, so you have no choice but to accept it.
Q: I enjoy reading
the good information you provide concerning trees. One method I've found
to control web worms is to attach a propane torch to a long pole and burn
the nests. I used to have them all over my cottonwood trees, but got rid
of them after burning the webs for a couple of years. Someone told me
that this disrupts the worm’s cycle. The drawback is dodging the
flaming webs as they fall to the ground. Dodging the webs can be hazardous
if standing on a stepladder and holding a 20-foot pole with a propane
torch taped to the end of it. I know this sounds like something out of
a Patrick McManus book, but it sure worked for me. (Bismarck, N.D.)
A: Yes, I have done
that, too, but never on a ladder or with a propane burner attached to
a long pole. You are a brave man. Your solution definitely will interrupt
the worm’s life cycle. Don't try this when you get over 60! Thanks
for the nice comments about the column!
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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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