Yard & Garden Line News
Volume 1 Number 6 July 15, 1999
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Fertilizing Reminder:
Deborah Brown, Extension Horticulturist
Some water soluble fertilizer choices
Photo credit: Minnesota Extension Service
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Remember that the heavy rainfall we've experienced has leached a
lot of nutrients deeply into the soil, especially soils that are on
the sandy side to begin with. Plants growing in containers and
hanging baskets are particularly vulnerable to nutrient defiencies
when rainfall has been abundant, and should be fertilized every
couple weeks. Even lawns, in some places, are a paler green than
they were before recent downpours.
Fertilize flower and vegetable gardens again, using a granular
product that can be scratched into the soil around the plants or,
if they've grown close together or are mulched, use a liquid
fertilizer such as Peter's Special, Miracle Gro, Rapid Gro, Schultz
Instant or others.
Same for roses and other shrubs; you'll want to stop fertilizing
woody plants in early August, though, so they can begin to harden
off for next winter. (Ugh, do we have to think about that
already???)
You CAN apply a lawn fertilizer half-strength if you feel it's
necessary, but only if you have the ability to keep your grass
well-watered on a regular basis, in summer's heat.
Plant Fall Veggies Soon; Then Eat and Enjoy!
Deborah Brown, Extension Horticulturist
Lettuce
Photo credit: Minnesota Extension Service
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Why eat vegetables? Because they taste good, of course.
Especially when they're plucked right out of your own garden or
picked fresh locally. There are plenty of proven health reasons
why we should all be eating lots of veggies, too. Dr. John
Weisburger of the American Health Foundation and formerly of the
National Cancer Institute wrote:
"If individuals eat five to nine helpings of vegetables a day, they
would be at a lower risk for a lot of diseases: heart disease,
hypertension and stroke, and many types of cancer, as well as
adult-onset diabetes. Vegetables and fruits are uniformly
preventive."
So it's agreed: really fresh veggies taste great and they're good
for you. Unfortunately, though, by the end of July some peoples'
enthusiasm for gardening activities has begun to wane. But many of
our favorite vegetables, especially salad crops, thrive and are
tastier (usually more mildly-flavored) when they mature under
conditions of longer, cooler nights. In the Twin Cities area, that
means planting seeds during the first or second week in August.
The first step is to remove all plant debris and weeds from the
area to be replanted. Then work in additional garden fertilizer,
such as 5-10-10 or 10-10-10, at the rate of one to two pounds per
thousand square feet. (Better yet; have your soil tested to see
which nutrients should be added. Most soils have plenty of
phosphorus already.)
Mid-summer planting is not quite the same as planting in early
spring. Warmer soil temperatures generally result in more rapid
seed germination. Drying winds and high temps also pull moisture
from the soil. To protect young roots, apply a light, two to three
inch deep mulch of dry grass clippings as soon as seedlings make
their appearance.
Water thoroughly and regularly, keeping in mind that it takes time
for roots to develop. If possible, water early in the day when
less moisture will be lost through evaporation and plants will dry
rapidly.
You'll be pleased to find that your seedlings face less weed
competition by August -- many annual weed seeds are programmed to
sprout earlier in the season. Some insect pests are less severe,
too, but you should still scout for them regularly.
Here are some vegetables to plant from seed in early August:
kohlrabi * leaf lettuce * onions
radishes * spinach * turnips
Finally, plant beet seeds right now for leaves, good in borscht and
salads, or very small roots for pickling or salads.
Petunias; Old-Fashioned and More
Deborah Brown, Extension Horticulturist
"Fantasy" petunias and other annuals.
Photo credit: Deb Brown
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Petunias are wonderfully reliable old-fashioned annuals that bloom
profusely regardless of what type summer our fickle Minnesota
climate presents us. As long as they receive five or six hours of
sunlight daily, they're usually splendid.
If you've got some blank spots in your garden, it's not too late to
plant petunias, provided you find some that aren't terribly
overgrown. (Try your local garden center or one of the larger
farmers' markets.)
If plants look healthy, but are too tall for their containers,
simply pinch them back to two or three inches and loosen or make a
couple shallow vertical slices through their root balls when you
transplant them. They'll branch rapidly in warm, sunny growing
conditions, and you'll have flowers again within a week or two.
To those of you who might say, 'petunias..... ho-hum', there are
exciting new developments in the world of petunias that you should
be aware of. Plant breeders have come up with two totally new
classes of petunias, making these popular annuals more versatile
than ever.
Until recently, garden centers offered two basic types of petunias,
"grandiflora" petunias (large-flowered) and "multiflora" petunias
(medium sized flowers, but more of them), both of which are still
available in a wide array of solid colors and bi-colors. Now those
categories are joined by petite "milliflora" or 'Fantasy' petunias
and spreading or "groundcover" petunias.
Milliflora petunias culminate years of work by Mary Hunsberger who
earned her phD here in vegetable breeding in the University of
Minnesota's Department of Horticultural Science, then went on to
become a flower breeder for Goldsmith Seeds in Gilroy, California.
As compact, miniature plants that produce abundant quantities of
perfect, small flowers, milliflora petunias help fill a niche
previously held by sweet allysum, lobelias and other small-statured
annuals. Unlike traditional petunias, each plant grows only eight
to ten inches tall, with flowers an inch to inch and a half across.
If you space them four to six inches apart in the garden they'll
merge as the season progresses.
There's no need to pinch milliflora petunias; the plants branch
well on their own, rather than growing tall and spindly. Because
of their form they are perfect for edging a garden. Their
diminutive size also makes them just right for massing together in
small space garden spaces.
Whereas millifloras are more delicate than traditional petunias,
spreading or groundcover petunias are "knock your socks off" bold.
'Purple Wave', 'Pink Wave', 'Pampas Fire' and other "supertunias"
only grow about six inches tall, but make quite a splash with long
arching stems cascading from the center of each plant. Like the
millifloras, they require no pinching in order to branch freely.
Space them about a foot and a half apart in the garden.
These spreading petunias cost more than ordinary petunias, but
they're well worth it! Their growth habit makes them ideal for
scrambling down a hillside garden, or planting atop a retaining
wall. And they're nothing short of spectacular in hanging baskets
and window boxes where they can trail two to three feet or more
over the course of the summer.
Their stems continue to grow, covered with new blossoms right up
until frost, provided they receive added attention in the form of
frequent watering and fertilization.
Caring for Petunias
Deborah Brown, Extension Horticulturist
Hanging basket
Photo credit: Beth Jarvis
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The most important requirement for growing any petunia successfully
is a location with plenty of light. Petunias need at least five or
six hours of good sunlight; they'll perform even better located in
full sun all day. The more shade they receive, the fewer flowers
they'll produce. (Impatiens are a better choice for colorful
blooms in shady places.)
Petunias tolerate lots of heat, and are relatively undemanding when
it comes to water. Watering petunias planted in the garden once a
week should be sufficient in all but the worst weather. You must
water thoroughly, though. Leave sprinklers on long enough to soak
the soil to a depth of six to eight inches every time you water.
Spreading or groundcover petunias are a different story; they
require water much more often to perform at their best.
Hanging baskets and other containers of petunias always need more
frequent watering, perhaps as often as daily, depending on their
size and the volume of soil they contain. Because all this
watering leaches nutrients through the soil, you'll need to
fertilize more regularly -- every other week -- to replace them.
Spreading or groundcover petunias grow so fast they must be
fertilized weekly with liquid plant food such as Miracle Grow,
Rapid Grow, or one of the other many good products meant for
blooming plants -- if you expect to maximize their growth
potential.
Bacteria Proliferate on Plants
Jody Fetzer, IPM Specialist, MN Landscape Arboretum
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Bacterial leaf spot
Photo credit: NCSU
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This summer I have seen more than the ‘normal’ number of bacterial disease
problems on herbaceous plants and trees. Bacteria can cause tip blight,
leaf spots and even kill limbs of trees. Rows in our apple orchards are
brown with dead leaves clinging to limbs of branches killed by fireblight.
This is a good year to find out which apples are resistant and which are
susceptible to fireblight bacteria. Lilac limbs may also die suddenly due
to a different bacterial infection, with symptoms very similar to
fireblight on apple. Today (7/9/99) I found purple coneflowers wilting –the stem
near the flower was dark brown for a length of about six inches (stem
above and below and roots were healthy)—it was caused by bacteria. This
spring I have found bacteria causing leafspot on nasturtium, geranium,
Rudbeckia goldstrum, zinnia, bittersweet and hydrangea.
It can be difficult to tell the difference between leafspots caused by
bacteria vs fungi, symptoms are often similar. Bacterial leafspots are
more likely to be angular and have a yellow halo (but sometimes they are
round and sometimes fungal leafspots may have a yellow halo). It is
important to correctly diagnose the causal organism because fungicides
will generally not provide protection against bacterial diseases. Without
a microscope you may never know for certain. Sometimes you can see
bacterial streaming if you cut through the infected tissue, place it in a
drop of water on clear glass and shine a light behind the specimen (is
stuff oozing out?).
When in diagnostic doubt, if a spray is needed, choose a copper compound
–coppers will help protect plants against bacteria and some fungi as well. Many different copper sprays are available in gard en centers. Chose one with the labeling needed for your plant (copper products tend to be vaguely labeled and Ok to use on a wide variety of plants).
Your best defense is to keep plants clean and dry, remove infected plant
tissue, cleaning your prun er with rubbing alcohol between cuts.
False Japanese Beetles
Jeff Hahn, Assistant Extension Entomologist
False Japanese beetle
Photo credit: Jeff Hahn
Japanese beetle
Photo credit: Ent. Dept.
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Strigoderma arboricola, is a native Minnesota insect. It has a strong resemblance to Japanese beetle which is a quarantine pest and present in just a few areas in Minnesota. Both beetles first start emerging late June or early July. While Japanese beetles are active through August, false Japanese beetles are present for only a few weeks and are generally gone by the end of July.
Although both beetles are the same size (7/16 inch long), you can readily distinguish between them. Japanese beetle has an emerald green prothorax (the first area behind the head) and coppery brown wing covers and generally looks shiny. There are 5 small patches of white hairs on each side of the abdomen and two on the tip of the abdomen (they appear as spots) . In contrast, false Japanese beetle is duller with a dark brown (with a hint of green) prothorax and tannish to brown wing covers. It completely lacks any white patches of hair on the side or tip of its abdomen.
False Japanese beetles are associated with sandy soil and have been common in Anoka, Washington, Sherburne, Benton, and Stearns counties. They feed on the foliage and flowers of various perennials and shrubs. They are particularly reported on roses. To manage false Japanese beetles, hand pick small numbers of them. When larger numbers are present, protect plants with an insecticide application, such as permethrin or carbaryl (Sevin).
Earwigs
Jeff Hahn, Assistant Extension Entomologist
Earwig
Photo credit: Jeff Hahn
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Earwigs have commonly been coming into homes since early July. They're about 5/8 inch long, reddish-brown, with short wings and forceps-like pincers at the tip of their abdomens. Earwigs love damp conditions. They're nocturnal (active at night) and hide where it is dark, like under stones, boards, bricks, and general debris. Earwigs are scavengers, feeding on plants and insects.
In your garden, they feed on many vegetables and flowers. Their damage appears as many small, irregular holes in leaves. Sometimes their feeding is confused for slugs. If you see damage to your plants but can't identify the source, go outside at night with a flashlight. Look under plants to find earwigs.
If you discover a few earwigs in your garden, that's not serious and you can ignore them. If you see a lot of earwigs, they should be treated to prevent injury to your plants. Protect plants with carbaryl (Sevin), chlorpyrifos (Dursban) or diazinon. Be sure to read all pesticide label directions very carefully before using.
However, earwigs are primarily reported as a problem in homes. They are just nuisances but they can be very annoying by their presence. Earwigs are also known to give off a bad smell. To keep them out of your home, caulk and repair spaces and cracks around the outside of your home. Also clean up debris around the house, such as firewood, stones, and lumber which can give earwigs places to hide close to your home.
If you find still find a lot of earwigs inside, spray around the foundation of your home with chlorpyrifos or diazinon. However, if earwigs are determined, some will still get into your home. Just remove those with a dust pan or vacuum. Fortunately, they don't reproduce indoors and are a problem just during the summer.
Ant Swarms
Jeff Hahn, Assistant Extension Entomologist
Swarms of ants are common now. These winged ants are reproductives, i.e. new queens and males. The fly out of their nests at the same time, usually in large numbers for the purpose of mating. After mating, the queens fly off in search of favorable sites to build their own nests.
Although nearly all ants swarm, different species do so at different times of the year. Right now, pavement ants, cornfield ants, and field ants are common. These ants all nest in the soil. Both pavement and cornfield ants are about 1/4 inch long while field ants can be a little larger. Because of their size, field ants are sometimes mistaken for carpenter ants. However, carpenter ants do not nest in the soil and swarm just during spring.
Pavement ants like to nest under objects, including concrete slab construction of homes. As a result, pavement ants swarmers can enter homes through cracks and be seen indoors. Cornfield and field ants, on the other hand, usually nest in exposed sites and are not normally found swarming inside homes. However, they still can be found nearby in yards.
Despite the impressive numbers that nests can generate, these swarming ants are harmless. They presence is also temporary, usually lasting just a few days. No control is necessary.
A Tale of Two Weevils
Jeff Hahn, Assistant Extension Entomologist
Two species of weevils have been abundant this year. Neither are normally noticed, however, some factor, perhaps the mild winter, has allowed these insects to become quite numerous. Fortunately, numbers of both weevils are beginning to decline for this year and shouldn't be around much longer.
Barypeithes pellucidus is a small (3/16 inch long) dark-colored weevil. It has been commonly found in homes in eastern Minnesota. There is very little information in the literature about this weevil. Reports do come from wooded areas and it is presumed that adult weevils feed either on the needles of conifers or the leaves of deciduous trees. They become a nuisance when they enter homes. They are harmless to people and property. Physical removal is the most practical control.
Polydrusus impressifrons is a slender, 1/4 inch long iridescent green weevil. It has been reported from forested areas in the northeast and north central areas of Minnesota. These weevils are not typically found in urban landscapes. This year they have been found in large numbers feeding on the foliage of many plants. The literature reports them particularly on birch, poplar, willow, and apple.
Adult weevils lay eggs on trees during summer. These larvae hatch and drop to the ground where they will feed on roots. It is not clear how they overwinter but they emerge as adults starting in late May. Individual weevils feed probably for 4 - 5 weeks. Feeding occurs until July. In most cases, Polydrusus feeding does no lasting damage to trees. Young trees should be protected when large numbers of weevils are present. Since Polydrusus is finishing its feeding now, spraying any more this year does not help trees.
Will these weevils be abundant again next year? That is hard to predict. For Polydrusus this is the second year they have been abundant. Both of these weevils are normally at much lower populations, suggesting a temporary peak in their numbers. It is likely that next year or the year after, these weevils will return to more average numbers.
Get the low down on this month's insect pests at Insects http://www.extension.umn.edu/projects/yardandgarden/Ent.htm
Focus on:
Bell Museum press release
and
Beth Jarvis, Yard & Garden Line
The Bell Museum is familiar to many of us who visited it on school field trips, yet a surprising number of Minnesotans have no idea of its existence. To Yard and Garden Line users, the Bell Museum is a free source of information on wildlife questions. The wildlife help line is staffed from 2 to 5 p.m. Monday through Friday, but callers can leave messages any time. (Call (612) 624-4771.)
Visitors view one of
the many dioramas.
Photo credit: Bell Museum
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For more than 125 years the Bell Museum has been Minnesota's gateway to the natural world. Come face to face with Minnesota's wildlife and explore our changing ecosystems. Research in biodiversity at the Bell Museum helps preserve and protect Minnesota's fragile ecosystems.
The Bell Museum offers award-winning classes, camps, and workshops for children and adults.
The Bell Museum is located at 10 Church Street SE, Minneapolis. The hours of operation are Tuesday through Saturday 9 a.m. to 5 p.m. and Sunday Noon to 5 p.m. For more information about the Bell Museum please call 612-626-9660 or visit the website at www1.umn.edu/bellmuse/.
The current exhibit is Wings of Paradise: The Great Moth Paintings of John
Cody.
The upcoming fall exhibit is Impressions of Nature: The Wildfowl Art of
Frank W. Benson.
This fall look for the Bell Museum's new out door diorama "The Encounter",
a dynamic sculpture garden!
Aster Yellows
Crystal Floyd, Plant Pathology technician
Normal carrot (left) compared to diseased
Photo credit: Plant Disease Clinic
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Marigolds with aster
yellows
Photo: Chad Behrendt
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Aster yellows is a disease that occurs on many different flowers and vegetables. In addition to asters, other flowers such as petunia, marigold, daisy, phlox, and gladiolus may be infected. Susceptible vegetables may include carrot, potato, and tomato.
Aster yellows is caused by a phytoplasma, a microorganism with similarities to both viruses and bacteria. The phytoplasma survives winter in infected plant material and surrounding weeds such as dandelion and plantain. In Minnesota, the phytoplasma is mainly dispersed by the aster leafhopper. These leafhoppers migrate or are carried by wind to Minnesota from southern states in the spring. They are light green in color, 1/8" long, and feed on the underside of leaves. When they feed on infected plants, they extract the phytoplasma along with plant sap. After an incubation period inside the insect, the phytoplasma can be transmitted to healthy plants during feeding by the leafhopper.
Symptoms of aster yellows differ depending on the plant infected, but common symptoms include stunting, yellowing, spindly stems, and distorted flowers with green, leaf-like petals. In addition, yields are reduced and vegetables may taste bitter. If you are unsure if aster yellows is present in your garden, place marigolds nearby. They are highly susceptible and will be good indicators of aster yellows infection.
Manage aster yellows by removing weeds to prevent overwintering of the phytoplasma. This reduces the number of infections the following spring. There is no cure for aster yellows. Infected plants should be removed and destroyed. Insecticides used to control leafhoppers are usually not effective in home gardens.
Brown Rot
Chad Behrendt, Extension Plant Pathologist
Brown rot on plums
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Brown rot is a common fungal disease of plums, cherries, and other stone fruits. Brown rot, like many other plant diseases this spring, has been stimulated by the cool, wet conditions. Abundant rainfall during flowering and fruit ripening has created the potential for serious fruit loss. Although brown rot can infect and destroy fruit after being harvested, primary losses occur while the fruit is ripening on the tree.
Brown rot most frequently survives the winter in infected fruit on the tree (called mummies) or on the ground. Brown rot can also survive in infected twigs. Spores released in the spring during periods of wetness are wind-blown and rain-splashed to healthy trees, where they infect and kill new blossoms. The fungus then proceeds to infect young twigs, which may become girdled and killed. Girdled twigs usually form cankers, which later produce spores called conidia. These spores serve as a source of inoculum for fruit infection.
Fruit may be infected during wet periods through wounds or natural openings, with immature fruit being more resistant to infection than mature (ripened) fruit. As a result, brown rot severity increases as the season progresses and fruits mature. Once fruit is infected, the fungus rapidly destroys the infected tissue. Fruit may become completely rotten within a few days of infection.
Brown rot initially appears as small brown spots on the infected fruit, but is most easily identified by the brown tufts of fungal material that later develop on the infected, rotten portion of the fruit. Twig cankers and infected blossoms are usually more difficult to identify, but can be observed earlier in the season.
Brown rot can be controlled with a combination of sanitation practices and fungicide applications. Remove all fruit from the tree and the ground at the end of the season. Fungicides may be needed if brown rot continues to be a problem or during wet years. A thorough spray program using fungicides containing chlorothalonil or captan should be followed. In addition, fruit should not be allowed to over-ripen, and should be handled carefully during harvest to avoid wounding.
Fireblight
Chad Behrendt, Extension Plant Pathologist
Dieback on branches, typical of fireblight
Canker on trunk
Photo credit: Chad Behrendt
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Are the branches on your crabapple or apple tree turning brown and dying? If so, your tree may be infected by fireblight. Fireblight is a serious disease that infects a variety of hosts including pear, mountain ash, cotoneaster, and others, as well as apple. This disease, caused by the bacterium Erwinia amylovora, causes death of the blossoms, fruit spurs, leaves, and shoots. The bacterium may also cause death of the larger branches and trunk, resulting in tree death.
Typical symptoms include browning or blackening of the infected foliage, darkened (reddish-brown) and sunken cankers on larger branches that later crack, and blackening and curling of the shoot tips. These curled shoots, called Shepherd’s Crooks, are indicative of fireblight infection.
Bacteria survive winter along the margins of cankers in infected branches, and become active in the spring about the time blossoms form. As bacteria become active, they begin to multiply and exude from cracks in the bark. This sticky, sweet substance, called bacterial ooze, attracts insects that carry the bacterium to newly formed flowers. Bacterial ooze can also be spread to flowers by rain splash.
Bacteria colonizing infected flowers multiply rapidly, producing large populations for dispersal by visiting honeybees and insects. Dispersal of bacteria contaminated pollen or nectar to nearby flowers can cause sudden and severe disease outbreaks. Bacteria can also be dispersed to healthy leaves and young twigs by driving winds and rain. As bacteria colonize infected branches, they may form girdling cankers that kill the branch.
Although fireblight can be a devastating disease causing severe dieback and even death of the plant, certain varieties are resistant to infection and sustain little or no damage. Therefore, one of the best management techniques is to plant resistant edible varieties such as Chestnut, Crab, Dolgo, Haralson, Liberty, Red Baron, and Red Delicious, or resistant ornamental varieties such as Adams, Adirondack, Camelot, and Lancelot.
Other management practices include maintaining plant vigor, avoiding over-fertilization in early spring, pruning of infected plant tissue, and chemical applications. Prune all infected branches 6 to 12 inches below the discolored area during dormancy. Sterilize your pruning tool in a 10% bleach solution or 70% alcohol before each cut. If your tree is highly susceptible or severely infected, prune infected branches 12 to 18 inches below discolored area as soon as possible. Make sure to sterilize your pruning tool before each cut. Mild infections can usually be controlled with thorough pruning, while severe infections may require chemical application. Bordeaux mixture or Streptomycin sulfate can be applied according to the label when needed.
Test your diagnostic savvy monthly with Disease Watch at: http://www.extension.umn.edu/projects/yardandgarden/Plpa.htm
Editorial Notes
Photo credit:
Beth Jarvis
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In upcoming issues, get a behind the scenes view of the Minnesota Mum Project, learn everything you ever wanted to know about the Soil Testing Lab, mycorrhizae, renovating raspberry beds, care and maintenance of marginal hardy trees and shrubs, selecting the right root stock for apple trees and using low maintenance grass mixes. Watch for them! If you have suggestions for subjects you'd like to see covered here, please let me know!
Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/projects/yardandgarden/. Our newly revised home page has clickable links to most of the components of the Yard & Garden Line, such as Bell Museum of Natural History, INFO U and the Soil Testing Lab. You'll also find links to the current issue of the
Plant Health Care Update and back issue archives.
If you have gardening questions, please call the Yard & Garden Line at (612) 624-4771.
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Happy gardening!
Beth Jarvis
Yard & Garden Line Project Coordinator
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Some water soluble fertilizer choices
Lettuce
"Fantasy" petunias and other annuals.
Hanging basket
>
Bacterial leaf spot
False Japanese beetle
Japanese beetle
Earwig
Visitors view one of
Normal carrot (left) compared to diseased
Photo credit: Plant Disease Clinic
Marigolds with aster
Brown rot on plums
Dieback on branches, typical of fireblight
Canker on trunk
Photo credit: