Yard & Garden Line News
Volume 1 Number 2 May 1, 1999
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Hackberry Psyllids Nuisance This Spring
Jeff Hahn, Assistant Extension Entomologist
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Psyllid
Photo credit: U of M
Entomology Dept. |
People have been finding psyllids (SILL-ids) in their homes this spring. Psyllids are small, gnat-like insects.
They are 3/16 " long and have lightly colored wings mottled with tiny dark spots. Despite their general
appearance to flies, psyllids are actually related to aphids, leafhoppers, and scales. During summer, these
psyllids form galls (abnormal plant growths) on the leaves of hackberry trees. They commonly overwinter
around buildings in late summer and fall and can be a household nuisance.
As the warm weather 'wakes up' psyllids that were overwintering in homes (e.g. in wall voids) try to get
outside. Many don't make it and become trapped indoors.
Psyllids are annoying because of their presence
but otherwise are harmless to people, pets, and property. Control of psyllids in the spring is difficult and
probably not practical. Physically removing psyllids, especially large numbers, is best accomplished with a
vacuum. Insecticide sprays have little impact on their presence in your home. Fortunately, this problem is
short-lived and eventually they either move outside or die indoors.
'Red Bugs' in Homes
Jeff Hahn, Assistant Extension Entomologist
People have been finding tiny 'red bugs' in their homes lately. These apparent pests are clover mites. These
creatures are not insects but are more closely related to spiders and ticks. They are about the size of a
'pinhead' and reddish or brownish in color. Under magnification, you can distinguish clover mites from other
mites because of their long first pair of legs.
These mites are usually found in lawns where they feed on the sap of grass, clover, and other plants.
Despite their presence in turf, they do not injure grass. In spring, clover mites that overwintered in or near
buildings often enter into those homes, sometimes in large numbers. Due to their small size, they have not
problem entering buildings through cracks and spaces in the foundation and around windows. They are
frequently found on the south side of homes and other sunny areas.
Clover mites are harmless to people and animals. They can stain fabric and other materials when crushed.
Otherwise they are harmless to property. Once clover mites are found in your home the simplest tactic to
control them is to remove them with a vacuum or to wipe them up carefully (avoid crushing them) with a damp
cloth.
To prevent them from getting into your home, treat the foundation of the house with an pesticide, such as
dicofol (Kelthane), chlorpyrifos (Dursban), or diazinon. You can also cultivate the soil in a band of 18 to 24
inches around the house. This acts as a deterrent to clover mites. Flowers can be planted to make use of
the area but don't space them so close that clover mites can use them as a bridge across the soil.
Landscape rock or wood chips are not effective barriers.
Mystery Bug
Jeff Hahn, Assistant Extension Entomologist
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Pseudoscorpion
Photo: U of M Ent. Dept.
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We have gotten several calls about a distinctive, yet strange look arthropod. People describe it as about 1/5
inch long, purplish or reddish, with conspicuous pinchers. This is a description of a pseudoscorpion.
Pseudoscorpions are not insects but are relative of spiders, ticks, and other arachnids. They do resemble
tiny scorpions with their conspicuous claw-like pinchers (actually pedipalps). But they lack a tail that true
scorpions possess.
Pseudoscorpions are predators on small insects and mites and are considered beneficial. They can walk
backwards as well as they move forward. Despite their fierce appearance, they are harmless to people. No
more than a few may wander into homes at a time. Physical removal is the only necessary control.
Watch for Eastern Tent Caterpillars
Jeff Hahn, Assistant Extension Entomologist
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Eastern Tent Caterpillars
Photo credit:
U of M
Entomology Dept. |
It shouldn't be long before we start finding eastern tent caterpillars. Although they are known to feed on many
trees, they will be most likely found them on apple, cherry, flowering crabapple, plum, and chokecherry trees.
They construct a conspicuous silken webbing or tent in the forks of branches and the trunk. These insects
use the webbing as a refuge at night and during cool or wet days. They come out to feed on leaves when the
weather is warm and sunny. Eastern tent caterpillars start feeding late April or early May in central
Minnesota and finish by late May or early June.
Eastern tent caterpillars rarely kill healthy, mature landscape plants. In most years natural enemies keep
eastern tent caterpillar numbers down. Even when feeding is severe, healthy, vigorously growing trees can
tolerate defoliation. Usually the worst damage these caterpillars inflict on trees is making trees less attractive
because of the tents.
You can manage these pests without using an insecticide. Wait for evening or a cloudy day when the
caterpillars are inside their webbing. Then remove the webbing and the caterpillars with a stick or broom.
Put the caterpillars in soapy water to kill them. You could also bury them or (where permitted) burn them.
It is not effective to spray the caterpillars inside the webbing with an insecticide; the caterpillars are protected
inside of it. But because these caterpillars leave their tents to feed on leaves, you can manage them by
treating the foliage with a product, such as Bacillus thuringiensis (e.g. Dipel, Thuricide), acephate (e.g.
Orthene), carbaryl (e.g. Sevin), or malathion. Bacillus thuringiensis is a bacterial insecticide that is very low in
toxicity, posing very little risk to people and pets. If the tree is flowering, spraying Bacillus thuringiensis also
protects pollinating bees.
Watch Honeylocust for Plant Bugs
Jeff Hahn, Assistant Extension Entomologist
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Honeylocust Plant Bug Feeding
Photo credit:
U of M
Entomology Dept. |
We expect honeylocust plant bug nymphs to be hatching soon. Egg emergence is associated honeylocust
leaf expansion. Immature plant bugs are light green, oval-shaped and between 1/16 - 3/16 inch long. They
resemble aphids but move more quickly than aphids. Nymphs feed for about a month before turning into
adults. Adult plant bugs are similar but are 1/4 inch long and have wings. Adults feed to mid-summer. There
is one generation each year.
Honeylocust plant bugs feed on the underside of leaves. They insert needle-like mouthparts into the foliage
which creates a whitish or yellowish speckled discoloration on the top of leaves. When honeylocust plant
bugs feed on newly emerging foliage, leaves, becomes dwarfed and disfigured. This injury can resemble
herbicide injury. In most cases, honeylocust plant bug damage does not seriously injure healthy, mature
trees and damage just affects its appearance. It is possible for large number of plant bugs to injure young or
unhealthy trees.
If your honeylocust is prone to plant bug feeding and you wish to protect it , especially if there has been
heavy feeding in the past, use one of the following insecticides: acephate (Orthene) carbaryl (Sevin),
diazinon, or permethrin. Make one application just after bud break or as soon as you see plant bugs. It is
important to treat early enough in spring to minimize injury to honeylocust. Most plant bug injury occurs as
leaves are just emerging.
Forsythias, Magnolias Spectacular in Twin Cities
Deborah Brown, Extension Horticulturist
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Forsythia
Photo credit:
Deb Brown
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Did you notice the beautiful bright yellow forsythias that started blooming around mid-April? And along with them,
loebner and star magnolias? In part, we can thank our second relatively mild winter in a row for their performance. Some
"zone 5" forsythias that only bloom once in a great while bloomed here this year. And marginally hardy plants like the
magnolias were covered top to bottom with fragrant, showy blossoms.
Luckily we don't have to depend on milder-than-usual winters to enjoy colorful flowering trees and shrubs early each
spring. We have two forsythias, 'Northern Snow' and 'Meadowlark' that are fully hardy in zone 4. Though all loebner and
star magnolias should perform well most years, particularly when planted in somewhat protected locations, the cultivar
'Royal Star' can withstand winter temperatures down to minus 35 degrees.
Coming right on the heels of magnolias and forsythias, lavender 'PJM' rhododendrons are a reliable harbinger of spring
every year. They do vary somewhat in color intensity, so it's a good idea to buy PJMs in bloom, or at least starting to
open, so you can choose what you like.
Nurseries and garden centers are filled with lovely flowering shrubs right now. It's the perfect time to add them to your
landscape. And don't forget, a flowering shrub makes a wonderful Mother's Day gift, too....especially if you're willing to
plant it for your mom.
Moss in Lawns; a Perennial Problem
Deborah Brown, Extension Horticulturist
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Moss
Photo credit:
Beth Jarvis
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If your lawn has a fair amount of moss, chances are it's a perennial problem. But before you can deal with it successfully,
you've got to understand the underlying causes.
For some reason, the first thing people think about when they see moss is that the soil must be too acidic. In most
instances, that just isn't the case. Never add lime to the soil, based on the observation of moss. Instead, if you suspect
your soil is highly acidic, have a soil test run (contact your local county extension office or the U's Soil Testing Lab at 612-625-3101).
Moss is more likely to be indicative of a shady location with compacted soil; possibly some nutrient deficiency, as well.
The shadier your yard, the harder it is to grow turfgrasses. Moss, on the other hand, is well-adapted to shade. If the lawn
is really important to you, it might be worthwhile having trees trimmed, thinned, or maybe even removed, to provide more
sunlight.
When soil is compacted it doesn't drain well. Moisture usually sits up at the surface -- which is just where moss needs it --
rather than penetrating the soil five or six inches down, which is what desirable grasses need to encourage good root
growth.
A low maintenance lawn is one that's fertilized only once or twice a year, with clippings left on the lawn to decompose and
recycle nutrients. If you fertilize less than this, there's a good chance that poor nutrient status also plays a role in why the
grass is thin and moss moves in.
You can rake moss out of your lawn using a heavy metal garden rake, but unless you're able to solve the underlying
causes, your efforts will only yield temporary results.
Create Your Own Container Garden
Deborah Brown, Extension Horticulturist
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Container Garden
Photo credit:
Deb Brown
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No doubt you've admired the lovely container gardens offered for sale at your favorite nursery or garden center. There's
no denying it; they are gorgeous. But why not have the fun of assembling your own container garden, choosing your
favorite plants and color scheme? It's still early enough to find a wide selection of plants and put them together for a mid-May debut!
Start out with a large container that has one or more drain holes. Since this pot will be outdoors in rainy weather, it's
imperative that moisture drains freely from the soil. Otherwise it will puddle up and plants will rot. If the pot is really
deep, fill the bottom three to six inches with plastic packing peanuts before adding potting soil.
Use fresh potting soil that has fertilizer incorporated right into it, or mix some slow-releasing fertilizer throughout the soil
yourself. Both Osmocote and Stay-Green sell fertilizer pellets that will carry your plants right through the growing season.
Pick plants that are suited to the amount of sunlight they'll receive; geraniums are great in a sunny location, but you won't
see many flowers if they only get a few hours of sun each day. Colorful coleus foliage, on the other hand, tends to bleach
out when exposed to hot, beating sun all day.
Make sure you choose some plants that are upright, some that trail, and some that could be considered "filler" flowers.
Then plant them close together so the container looks full from day one.
Using Borax on Creeping Charlie
Deborah Brown, Extension Horticulturist
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Creeping Charlie
Photo credit:
Mn. Ext. Svc.
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Anyone who's battled creeping charlie in the lawn knows the weed is a formidable enemy. Often it's because people spray
broadleaf weed killers early in the season rather than in autumn when this perennial weed is more vulnerable. And often
the problem stems from shady conditions that favor creeping charlie over grass. If you kill the creeping charlie, but you
can't get anything to grow vigorously enough to replace it, the weed reappears.
Borax is just one more "weapon" you can try on creeping charlie. Buy Twenty Mule Team Borax, then apply it according
to the following directions. Apply it now, and look at the lawn in autumn to assess its value.
Boron, the natural herbicide in borax, will not break down or dissipate in the soil, so you can only use it once or possibly
twice in the same area. Once too much has been applied, not only will creeping charlie die, but the desirable grasses will
die too, and the only way to sod or re-seed would be to scrape up and replace the "contaminated" soil.
DIRECTIONS:
Dissolve 10 oz. of Twenty Mule Team Borax in 1/2 cup of warm water.
Dilute this solution into 2 1/2 gallons of water.
Spray the mixture evenly over 1,000 square feet of lawn.
Again, remember, you can only do this safely for two years. If creeping charlie is still a problem, you'll have to resort to
standard herbicides -- or learn (as many folks with shady yards have done) to live with it.
Four Myths About Turf
Reprinted with permission by Wayne Kussow, Dept. of Soil Science, University of Wisconsin
Myth #1: Conversion of farmland into turf areas increases surface and groundwater
contamination with sediment, nitrogen and phosphorus.
This myth persists because the public is uninformed, misinformed, or certain groups choose to
ignore current scientific evidence. The facts are that while the amounts of runoff water from
agronomic crops and turf may be similar, losses of sediment, nitrogen, and phosphorus are worlds
apart. This is evidenced by the following research data.
The data show:
Sediment losses from agronomic crops are measurable in terms of tons per acre. Losses from turf range from zero to 15 to 20 pounds per acre.
Nitrogen in runoff water totals 100 to 200 times more for agronomic crops than for turf,even though annual nitrogen fertilization rates for turf often equal or exceed those for agronomic crops.
Phosphorus in runoff water averages 1 to 6% of the amount from agronomic crops.
Nitrogen leached each year from crop land often is in the range of 20 to 40 lbs./acre. The
figure for turf is 0.2 to 2.2 lbs./acre.
Nitrate-nitrogen concentrations in leachate from agronomic crops often exceed the U.S.
drinking water standard of 10 mg L-1 by 25 to 100%. Nitrate-nitrogen concentrations in
leachate from turf are commonly 35 to 95% below the drinking water standard.
Myth #2: Subsoil compaction during building construction and the layering of topsoil
over subsoil for turf establishment greatly increases runoff and must be regulated.
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Preparing clay soil for sodding
Photo credit:
Bruce Giebink
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The fact is, in climates such as that in southern Wisconsin, 60% or more of the annual runoff
from turf is from frozen soil. During the growing season, the influences of subsoil compaction
and topsoil layering on runoff are negligible except when 2 inches or more of rain falls on already
wet soil. The net results are that subsoil compaction and topsoil layering have no significant or
consistent effects on runoff or nitrogen and phosphorous losses.
Particularly noteworthy , are the data that show that, on average, more than 60% of the nitrogen
and 80% of the phosphorous in runoff water from turf comes when soil is frozen. This
observation is consistent with reports that the phosphorous load in urban storm water is primarily
in snow melt. A secondary flush of phosphorous is associated with leaf fall in autumn.
Myth #3: Natural organic fertilizers are less contaminating than "synthetic"
fertilizers.
As noted by other researchers, the data shows that nitrogen and phosphorous losses from turf
fertilized with natural organic or synthetic are equally low and do not differ significantly. The
same holds true for liquid versus dry forms of fertilizer (Gross et al., 1990).
Myth #4: Banning fertilizer use on turf in urban areas will protect or improve surface
and groundwater quality.
The fact is that failure to fertilize turf leads to declines in ground cover and stand density. After a
single year without fertilization, runoff from the unfertilized turf may exceed runoff from
fertilized turf by 30% or more. This, in turn, leads to more runoff loss of nitrogen and
phosphorous from unfertilized than fertilized turf.
Nitrogen leaching from turf may be increased somewhat by fertilization, but clipping management
has even greater effects. Mulch mowing, as compared to clipping removal, may increase the
amounts of nitrogen leached by 50% or more.
Managing Disease in the Home Garden
Chad Behrendt, Plant Pathologist
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Vegetable and flower garden
Photo credit:
Beth Jarvis
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Every year homeowners are plagued by a variety of diseases, which disfigure flowers, rot produce, and shorten the life expectancy of garden plants. Whether you are growing flowers or vegetables, there are a number of practices that you can apply to help minimize plant disease.
To begin, start with disease-free seeds and/or transplants. Do not buy plants that look unhealthy; if they look diseased they probably are diseased. When planting your gardens try to change the location of your plants from year to year. Crop rotation helps reduce the severity of soil-borne pathogens. Many plants now contain resistance to common diseases, so use resistant varieties whenever possible.
Next, establish good cultural practices. These cultural practices improve the health and vigor of the plant, and modify environmental conditions that promote plant disease. Follow these cultural practices to ensure a healthier garden:
- Control weeds within and around your garden since they may harbor plant disease.
- Water plants early in the day so the foliage can dry before evening.
- Water plants at ground level to reduce the splashing of spores from one leaf to another.
- Maintain plant vigor by properly watering, fertilizing, and mulching plants. Proper mulching may also help reduce plant disease by preventing the splashing of fungal spores from debris in the soil to leaves on the plant.
- Improve air circulation and reduce moisture by providing adequate spacing.
- Avoid working in the garden during wet or rainy periods.
- Monitor plants regularly for plant disease, detect early infections and promptly remove infected leaves or heavily infected plants.
In most cases cultural practices should minimize the severity of plant disease. However, if you have had a problem with a specific disease in the past, you may consider applying a fungicide as a preventative measure, before the disease appears. Most fungicides are preventative, not curative; they are able to prevent uninfected leaves/plants from becoming infected but are not able to cure previously infected leaves/plants. If plant disease has not been a problem previously, you may apply fungicides as needed once the disease appears in the garden.
Black Knot: 'Old persistent'
Chad Behrendt, Plant Pathologist
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Black knot
Photo credit:
U of M
Plant Disease Clinic
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Every year the clinic receives numerous calls on the fungal disease black knot. The characteristic large, crusty, black growths are a common sight on the branches of most cherry trees (Prunus sp.). Often, the majority of branches will be covered by black knots making the tree aesthetically displeasing.
The ubiquitous nature of black knot makes control and management difficult. Typical control measures include pruning knots during dormancy and destroying them, pruning new swelling and knots as they appear later in the year, and applying a dormant season fungicide.
Although, it is too late to apply a dormant season fungicide this year, you can still prune out all knots and swellings. To prevent knots from sporulating, prune them as soon as possible. To reduce the risk of spreading the disease to healthy branches, sterilize your pruning tool between each cut with a 10% bleach solution. Wild cherries may also be infected, so remove all surrounding cherry trees whenever possible.
Identifying White Pine Trees Infected by Blister Rust
Chad Behrendt, Plant Pathologist
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White Pine Blister Rust
Photo credit:
Robert Blanchette
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White pine blister rust, a fungal disease infecting both white pine and Ribes sp. (currant and gooseberry), is easily identified in early spring. Orange-yellow pustules formed beneath the outer bark, rupture the bark giving the tree a blistered appearance.
These blisters may appear on the branches or the main trunk of infected trees. As the pustules produce spores, a light orange-yellow dust will cover the branch or trunk of the tree. Older blisters will appear pitted or cankered and darker in color.
Spores produced on white pine in the spring are windblown to nearby Ribes species, where they infect leaves. Throughout the summer the fungus continues to reproduce and infect Ribes species by producing repeating spores, called urediniospores. In late summer and fall the fungus produces a different spore, called a basidiospore, which is windblown to nearby white pine. Infection begins when basidiospores land on healthy needles. It takes a period of years before symptoms appear and the fungus is able to reproduce. When the fungus does reproduce pustules will rupture the bark, again giving the branch or trunk a blistered appearance.
There are no chemical control measures or resistant varieties of white pine available. However, proper tree care along with therapeutic pruning can maintain and cure white pine blister rust infections.
For more information on the life cycle go to:
Yard and Garden Brief: White Pine Blister Rust at http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/P442whtpineblstrst.html.
Apple Scab Reminder
Chad Behrendt, Plant Pathologist
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Apple scab
Photo: U of M
Plant Disease Clinic
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Now that the leaves on apple trees have emerged, begin to inspect your apple and/or ornamental crabapple trees for black or olive-green leaf spots.
If infection is low and rainfall is minimal you do not need to apply fungicides. Once infection begins to appear, monitor trees and rainfall more closely. If prolonged periods of wet weather are predicted, you may consider applying fungicides.
If you are growing apples for consumption and are following a spray program, continue to monitor the severity of infection and predicted rainfall. Remember, you may be able to delete sprays if no rain is predicted.
Are Your Hollyhocks Rusting?
Chad Behrendt, Plant Pathologist
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Hollyhock rust spores on flower buds
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Yes it is true. At the Yard and Garden Clinic, we have already identified rust on hollyhocks. The infected plants were no larger than a few inches in height, but were covered with rust fungi. Unlike other rust fungi, hollyhock rust completes its entire life cycle on just one host.
Initially, symptoms appear on the upper leaf surface as orange or yellow spots. Later, reddish-brown (rust colored) pustules (spots) appear on the under side of the leaf. These pustules produce spores, which reinfect the hollyhock plant. Pustules and spots may also occur on the stem of the plant. Severe infections can occur during wet periods, as spores are splashed from infected leaves and debris to healthy leaves.
To manage hollyhock rust, begin with healthy transplants or seeds. Keep plants healthy and vigorous by properly watering and fertilizing. Water plants at ground level early in the day, and provide adequate spacing and sunlight to reduce the amount of moisture available on the leaf surface.
Monitor plants and remove early infections by destroying leaves or severely infected plants. Control weeds in and around the garden. Finally, at the end of the growing season, thoroughly rake and remove all debris from the garden to reduce the severity of infection next year. If you have had problems with hollyhock rust in the past, you may consider applying a fungicide early in the season or at the first sign of infection. Bayleton should be effective. Read the label for directions.
Paging Sherlock Holmes!
When it comes to disease diagnosis, are you a regular Sherlock Holmes? Would you like to be?
Chad Behrendt has converted his former monthly Yard & Garden Line Plant Disease
article into a monthly disease quiz. It's currently under "Plant Diseases" on the website but soon will become "Disease Watch".
Check out at: http://www.extension.umn.edu/projects/yardandgarden/Plpa.htm
Thank you!
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