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December
1, 2005
Hortiscope
Ronald C.
Smith, Horticulturist
NDSU Extension Service
Q: We have five Victoria
plum trees in our orchard. They have produced fruit each year, but this
year, in the very ripe plums, there is a pale, pink grub inside. The underripe
plums seem fine (but still not sure we should eat them). We have chickens
in the orchard, so any treatment would have to be OK for them. When we
bought the house three years ago, there was a white ring around the trunk
of each tree. What is the white ring? (e-mail reference)
A: The best thing
you can do is harvest the plums and pick up those that fell off the
tree. Destroy those that have the plum curculio grub inside. Sanitation
is important in grub control, so do a good job of cleaning up the area
this fall. Next spring, before the tree leafs out, spray the tree with
dormant oil. The white ring was probably whitewash to protect the tender
bark from sunscald during winter the months.
Q: I talked to a homeowner
who always has rust problems in her lawn. Her grass mix is merit and park
Kentucky bluegrass, creeping red fescue and perennial rye grass. Her management
practices are sound and I am not getting rust calls from other homeowners.
Is there a difference in rust susceptibility to various varieties of Kentucky
bluegrass? (e-mail reference)
A: You bet there
is. A lot depends on the care given. If a turfgrass, such as park, is
irrigated and fertilized on a regular basis, it will be more prone to
rust than if given minimal care. Some of the rust-resistant cultivars
are glade, America and parade. Keep in mind that there are more than
a dozen different races and species of rust fungi that are known to
infect turfgrasses and all are affected in varying degrees by this ubiquitous
fungus. There are a number of fungicides that can help control rust,
such as chlorothalonil, maneb and zineb. Since the fungus typically
appears in the fall when turfgrass growth slows, I encourage people
to fertilize lightly and collect the clippings so the grass can “outgrow”
the pathogen. With the infected grass blades collected, a source of
the inoculum is removed.
Q: Someone stopped
in who has a couple of rows of raspberries that he moved to a new location
a few years ago. Before the move, the raspberries produced fruit, but
not now. He says there has been very good vegetative growth, just no fruit.
Any thoughts? Also, what would be your choices for some varieties of shrubs/bushes
to be placed in a nonwatered location and wouldn’t exceed 3 feet
in height when mature? (e-mail reference)
A: The raspberries
could be producing their vegetative canes this year and will bear fruit
next season. Remember, the raspberry is a biennial cane that is vegetative
the first year, bears fruit the next, but then dies at the end of that
year. Shrubs that wouldn’t exceed 3 feet are potentilla, snowmound
spirea, Annabelle hydrangea, dwarf or Arnold honeysuckle, hibiscus,
redleaf barberry and compact European cranberry bush viburnum. Not a
complete list by any means, but about all I can think of right now.
Q: We planted four
long rows of corn this year. The ears ended up being very short or what
you call nubbins. The bees worked hard on pollinating the corn. What am
I doing wrong? (e-mail reference)
A: Instead of planting
four long rows, try planting eight short rows next year. Obviously the
pollen, which is wind driven, did not reach the silk in sufficient quantity
to fill out the ears. I think if you alter your planting next year to
a more block system, the results will be much better.
Q: I have several
maple trees on my property, but am having a problem with only one. I noticed
that on the underside of the leaves there are green growths on top of
or within the veins. Some leaves have so many growths that they actually
are shriveling inward. The problem seems to be affecting more than half
of the leaves. Is this a disease, insect or something else? Will it affect
the health of this beautiful 40-year-old maple? (e-mail reference)
A: These outgrowths
or pouches are microscopic eriophyid mites. Their feeding habits cause
an overstimulation of plant hairs, which produce the growths known as
erinea. The mites commonly are found on silver and sugar maple foliage.
In spite of the appearance of some of the leaves, their effect on the
tree is minimal. These arthropods come and go. Natural forces, such
as weather or predatory mites, mostly control them. Because they cause
no harm, spraying is not recommended. Even if it were recommended, the
timing would be very difficult.
Enjoy this unique feature of nature, knowing that your trees will be
OK.
Q: When is the best
time to transplant rhubarb plants? Also, do you have any books out about
gardening? (Carrington, N.D.)
A: Spring is the
best time for transplanting, before new growth. I don’t have any
books out, but I do have plenty of publications. A book is likely sometime
in mid-2006. Go to www.ext.nodak.edu/extnews/hortiscope/contents.htm
on the Web and work your way around the horticultural subjects of interest
to you.
Q: I’ve been
reading your columns and think they are very good. The columns made me
start to think about my tree! I bought a cutleaf weeping birch at a 75
percent off sale. It looked OK when I transplanted it three weeks ago.
The top branch (looks like the leader branch) had one small branch with
leaves at the top. Below that are numerous branches. I put in green, light
root starter and the tree is budding like crazy. But, the top bunch of
leaves died and also possibly the branch. The tree has about eight leaves
with scales that I am getting rid of with systemic insect killer. I read
that such problems are caused by bronze birch borers, but not if the tree
is less than a year old. What do you think is the reason for the top dying
off? (e-mail reference)
A: Good moves on
your part! I think the tree will be OK. Everyone told me I was crazy
to plant one 20 years ago. Now it is the most dominant part of our property
and looks beautiful. Keep it watered and the turfgrass away from it!
Q: I really enjoy
your gardening column. I have learned so much from you. You have helped
me in the past, but now I need your help again! I have some chive seeds
that were given to me. When do I plant them? Also, I have this weed, “common
purslane,” all over my garden. How can I control it? (Dazey, N.D.)
A: You might want
to save the chive seeds until next spring. “Common purslane”
is an annual weed that is edible and tasty when mixed with other salad
greens. To get rid of it, you can use Treflan early in the season as
a pre-emergent herbicide. It is found in products with the label name
Greenview Preen. Be sure to read the label directions when using this
material. Another way to control purslane is to cover the soil with
about 3 inches of organic mulch. Thank you for your nice comments about
the column. It is great having a loyal reader like you!
Q: I live north of
Bismarck on a lot with many trees used as a shelterbelt. I have noticed
rings of dead grass and thought it was from our zero-turn lawn mower.
However, the rings have multiplied in places we didn’t usually turn
with the mower. I did some Internet surfing to find out we have necortic
ring disease. Some call it fairy ring disease. I checked out some fungicides
at our local garden store, but the cost would be more than $900 to treat
our lawn. Please let me know what we can do to get rid of the problem
and prevent it from returning. I love your column! (e-mail reference)
A: Thanks for the
compliment! Let’s sort out the two diseases. Many soil-inhabiting
fungi of the class known as basidomycetes cause fairy ring. The fungus
species is not important in this case because they all have the same
basic symptoms. The circles get larger and the fungus moves through
the organic matter in either the soil or thatch. This activity breaks
down the nitrogen tied up in the organic matter, which stimulates growth
ahead of dead or dying turf, as well as behind it in many cases. Often
the cause is from old stumps and roots from previously forested land,
construction debris of an organic nature or simply from a high level
of thatch. There is no chemical control. The symptoms can be masked
by nitrogen fertilization, so that the green rings will not be as evident.
The other option is to dig everything out. Necrotic ring spot (Leptosphaeria
korrae) is one of the most common patch diseases on cool-season Kentucky
bluegrass. The disease shows up as small rings of necrotic grass, often
with a “frog-eye” appearance, such as green grass inside
of a dead circle of grass. While there are chemical controls for this
disease, cultural practices can sequester it quite well or eliminate
it. The use of organic fertilizers, such as Milorganite, Lawn Restore
and Turf Restore, have been shown to biologically control this disease
by stimulating beneficial microorganisms that are antagonists to this
pathogen. Chemicals, such as Tersasn 1991, Fungo 85 and Spot Kleen,
can be used to control this disease, but I encourage you to attempt
good cultural practices to get your turf in shape. Fertilize at least
annually, water when needed and mow on a frequent, timely basis.
Q: We have hackberry
trees that are not growing. We had the soil tested as you suggested. The
pH level is 7.7, the phosphorus is 146 parts per million (ppm), the potassium
level is 246 ppm and the sulfur level is 13 pounds per acre. Nutrients
in the soil were very low at 5 pounds per acre. We took this sample about
5 inches down. Will this information help you tell us why the hackberry
trees are yellow, drying up and not growing? Maybe this area is not meant
to grow trees. (McVille, N.D.)
A: The soil test
results reveal nothing that should keep the tree from growing normally.
I have to think it might have something to do with the planting depth.
Since being alerted to this problem by a colleague at the University
of Minnesota a couple of years ago, I am amazed at how many trees are
planted too deeply. A covering of 3 to 4 inches of soil over the crown
will result in the gradual decline of the tree through early leaf drop,
leaf discoloration and reduced growth until the tree is killed.
Q: The crabapple trees
that line the avenue in our neighborhood are looking very distressed.
They bloomed gloriously this spring, but now look like they are dying.
They had drooped leaves all summer. We have one in our yard that is in
the same condition. Are they a lost cause or can they be saved? What do
you recommend? (Fargo, N.D.)
A: It could be apple
scab, which is a plant disease caused by the fungus Venturia inaequalis.
It also could be a rust fungus known as cedar-apple rust. Both cause
early defoliation. The rust fungus is more isolated, while the scab
fungus is more universal in spread, so I believe this is what you are
seeing. Clean up all the leaves and fruit this fall. Next spring, spray
the trees with lime-sulfur while the trees are still dormant and again
after leafing. Use a fungicide known as Captan. Repeat again in 10 to
14 days.
Q: I have decided
that I need to move my morden blush rose because it doesn’t get
enough sun in its present location. Do you have any suggestions about
transplanting roses? (e-mail reference)
A: Allow it to go
dormant this fall, cut it back hard, and dig it out and move it to the
new location. Replant at the same depth. Water it well and mulch just
before freeze-up.
Q: I have a hydrangea
bush that is not doing well, so I would like to move it to another spot.
When is the best time to do the transplant? I also would like some advice
on red maple trees. Our tree hasn’t grown to any extent since we
planted it a few years ago. Should we replace it or is there something
else we could do to help it grow? (Gackle N.D.)
A: Move the hydrangea
after a couple of hard frosts. The maple could be planted too deeply,
which is a common mistake. The crown should be right at the soil surface.
The crown is where the stem and root system meet. If your tree is planted
to deeply, pull the soil away from the trunk of the tree to where the
crown is. That may improve the vigor and appearance of the tree.
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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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