Yard & Garden Line News
Volume 1 Number 3                                                              May 15, 1999
Features this issue:
 Chironomid Midges
Tree Insects:
      Pine Needle Scale   Birch Leaf Miner    Eastern Tent Catterpillar    European Pine Sawfly
Ticks
Bed Bugs
Syringa: from vulgaris to sublime
     Lilac Selection Tables
Using Crabgrass Preventers
Fertilize Lawns Safely
Advice to New Gardeners
Moving Houseplants Outdoors for Summer
Rings Around the lawn
Proof is in the Picture
Rain Drops Keep Splashing All the Spores
Dieback of Dogwood
It's Time to Spray for Rhizosphaera Needle cast
Editorial Notes
Chironomid Midges
Jeff Hahn, Assistant Extension Entomologist

Chironomid midge
Photo credit: Jeff Hahn
A mosquito-like insect, known as a chironomid midge has been commonly seen this spring. Chironomid midges are slender and similar in size to their biting cousins. However, midges lack any biting mouthparts and can not bite people. Midges also have feathery antennae which helps to identify them.

Midge larvae are aquatic, living in slow-moving rivers, streams, lakes and ponds. Midges are found in clean bodies of water as well as polluted ones. They are also known to develop in damp soil and other semi-aquatic areas. It is possible that the mild winter may have allowed midges to be somewhat more common than normal. However, midges are always most common during spring even though they may seen throughout the season.

What really draws people's attention to these insects is the large swarms that midges form as they mate. Although they do not bite people, they can be quite annoying just by their presence. People trying to pass through such a swarm find midges in their faces, eyes, and mouths.

Control of midges is impractical and unnecessary. The mating swarms are temporary and will go away on their own. Remember that they are harmless to people (even including the occasional one or two that may be swallowed).

For people that wish to expedite their departure, however, direct controls are not very effective. If you try to fog them, the result is temporary and more midges will return to the area. Treating water where larvae are developing is not practical because of the enormity of all the potential areas when midges can be. Adult midges are strong enough of fliers that they can enter from beyond treated areas.

Tree Insects
Jeff Hahn, Assistant Extension Entomologist

pine needle scale Pine needle scale
birchleafminer Birch leaf miner.
tentcaterpillars Eastern tent caterpillar.
europinesawflies European pine sawflies. All Photos: :U of MN Entomology Dept.
In general, insect activity is about 7 - 10 days ahead of schedule. This is reflected in the samples and calls we are currently receiving.

Pine needle scale crawlers were found on May 7 on a sample submitted to the Yard and Garden Clinic. Insecticide treatments are not very effective against adult scales. Pine needle scales need to be managed when the vulnerable crawlers have hatched. You can verify whether crawlers are present on your pine by holding a white paper plate or piece of paper under an infested branch. Tap the branch and look for the presence of tiny reddish 'bugs' that have fallen to the white paper.

We observed early birch leafminer mines in St. Paul on May 7. For people who wish to manage birch leafminer feeding, this is the best time minimize their injury. Remember that leafminer feeding primarily affects the appearance of birch and its health is normally not seriously impacted. The longer leafminers feed, the larger the mines become and the less effective treatments are. Check individual trees as mines will not all begin at the same time. Also the degree of infestation will vary from tree to tree.

Eastern tent caterpillars have been reported. People normally first notice their tents which occurs in the crotches or forks of limbs. Their feeding is not normally serious. You can eliminate these pests nonchemically by waiting for the caterpillars to return to their webs. Then remove the tents with the insects with a stick or broom handle. You can dispose of them by putting them in soapy water, burying them, or (where permitted) burning them.

We received a sample of European pine sawfly larvae on Mugho pine. As of May 10, most larvae were about 3/8 - 7/16 inch long. This is good time to treat them as feeding damage has not become too severe yet. Because these insects feed on the older needles, the tree or shrub can tolerate most feeding injury. Once these sawfly larvae are about 3/4 inch long, they are full grown and it is not effective to treat them.

Ticks
Jeff Hahn, Assistant Extension Entomologist

Amer dog tick American dog tick
Photo credit: U of MN Entomology Dept.
We have been receiving tick samples more commonly over the last five weeks, especially blacklegged ticks (formerly deer ticks) and American dog ticks (also known as wood ticks). It is important to correctly identify ticks, as blacklegged ticks are potential vectors of Lyme disease and Human Granulocytic Ehrlichiosis. American dog ticks are not know to transmit either disease. Get unknown ticks identified when there is a question about possible disease transmission.



Bed Bugs
Jeff Hahn, Assistant Extension Entomologist

bedbugs Bed bugs
Photo credit: U of MN Entomology Dept.
We have received a number of bed bug inquiries over the last four weeks. In Minnesota, we have two species of bed bugs that people may encounter, the human bed bug and the bat bed bug. Both are very similar in appearance and can only be distinguished by a couple of small, subtle characters. They somewhat resemble a tick being small (about 3/16 inch long), round, brown, and wingless.

Both bed bug species are pests because of their ability to bite people. The presence of bat bed bugs, though, also indicates the presence of bats in the building. These bugs are nocturnal and feed while people are sleeping. The victim normally doesn't feel the bite, although later the site of the bite will often itch and possibly swell and leave a lump.

During the day, bed bugs hide in cracks and crevices. You can find them in folds and seams in mattresses and bed covers, in upholstery of furniture, behind baseboards, pictures, clocks, peeling wall paper and other similar protected, dark sites.

There are several steps in controlling bed bugs. Give bed bugs fewer hiding places by sealing cracks and spaces, repairing or removing loose wallpaper, and removing pictures, posters or other objects where bed bugs may hide. Apply an insecticide into cracks and crevice where bed bugs may hide. A home dweller can use an insecticide found in aerosol spray can labeled for ants and roaches. They can also hire an experienced pest control company to control their bed bugs.

If you have a problem with bat bed bugs, that means you also have bats living in your house. To control the bed bugs, you need to exclude the bats from your home to remove the source of the infestation.

Syringa: From vulgaris to sublime
James B. Calkins, Coordinator, Master of Ag.--Horticultural Science
and
Beth R. Jarvis, Yard & Garden Line Project Coordinator

sensation 'Sensation'
Photo credit: Jim Calkins
Lilacs are a welcome harbinger of spring. For many of us, huge bouquets of fragrant lilacs gracing the dining room table are reminders of a simpler time. Now, while the lilacs are in full bloom, is an excellent time to consider adding the adaptable, dependable, lilac to your landscape. Use the tables in this article to help you choose the right lilac for you and your landscape.

The name lilac stems from the word nilak, Persian for bluish. In Arabic, nilak became laylak and then lilac in Spanish. Lilacs belong to the family Oleaceae, the olive family, and comprise the genus Syringa (from Greek, syrinx meaning flute or hollow stems) and includes about 30 species of deciduous shrubs and trees native to Asia and southeastern Europe.

Historically, lilacs have been one of the most popular groups of woody landscape plants. They are excellent for massing, screening, or in the back of the shrub border. They are also used for hedges and as specimen plants. Most lilacs are hardy in the upper midwest - in fact lilacs require exposure to substantial winter chilling (at least 850 hours at temperatures below 45F) in order to thrive and flower and are generally not heat tolerant. For this reason, few lilacs will grow south of USDA Cold Hardiness Zone 7.

The common lilac (Syringa vulgaris) is native to southeastern Europe and is the most commonly planted species of lilac. There are perhaps thousands of cultivars most of which are of French origin, hence the term French lilacs.

Twin Citians who plant common lilacs at their northern lake place and in their metro area yards will enjoy a longer bloom time as lilacs bloom in the metro area around mid-May and by late May or early June farther north. Planting other species can extend the bloom time. For example, early and hyacinth lilacs bloom prior to common lilacs and Japanese tree lilacs and others bloom later.
Japanese tree lilac Japanese tree lilac
Photo credit: Beth Jarvis

Any of the shrub lilacs can be pruned to tree form, but the term tree lilac generally refers to the Japanese tree lilac (Syringa reticulata) and perhaps the Pekin lilac (Syringa pekinensis).

Flowers come in a variety of colors including white, cream, pink, lavender, purple, violet, and magenta and are borne in showy thryses (panicles). Some cultivars have bicolored flowers such as `Sensation' which has purple flowers with white edges. Flower color is affected by soil pH. Lilac seedheads contain many individual fruits (capsules) which split open (dehiscent) to release their seeds when ripe. Seedheads are often provide winter interest.

Lilacs are available in many sizes and colors, ranging from the compact, petite lavender-pink flowered Meyer lilac to the Japanese tree lilac which can attain heights of 30 feet and has ivory colored flowers. The common lilac, Syringa vulgaris, generally grows to 12-15'.

Meyeri S. meyeri
Photo credit: Jim Calkins
Lilacs need full sun and a moist, well drained soil to thrive and bloom. Although lilacs prefer a slightly acidic soil, they are generally pH adaptable and will perform well on most sites except those that are excessively wet. The increasingly popular Japanese tree lilac is an excellent choice for heavier, clay soils. It is also tolerant of road salt making it a fine choice for boulevard plantings. Once established, lilacs are often quite tolerant to conditions that would otherwise be detrimental such as heat and drought.

To help you decide on possible lilacs to add to your landscape, here are two lists. The first is of lilac species. The second is a list of cultivars of some of the common species. Hardiness zones and growth characteristics are included.
For lilac enthusiasts there are additional species and many more cultivars available. Although less common, sources may be found in the Source List of Plants and Seeds, Andersen Horticultural Library, Minnesota Landscape Arboretum, phone (612) 443-2440. Most lilacs mentioned in this article are available from your local garden center. Some of the more exotic varieties may be found at Wedge Nursery, Route 2, Box 114, Albert Lea, MN 56007, phone (507) 373-5225.

Botanical Name Common Name Flower Characteristics Height Growth Habit & Other Traits USDA Cold Hardiness Zone
Syringa × chinensis Chinese Lilac single; white, purple, rose, red 5 to 8 feet nonsuckering shrub 3
Syringa × henryi> Henry Lilac single; pale purple; late May early June 8-12 feet Partially shade tolerant. Pubescent midrib on lower leaf surface. 4, possibly 2-3
Syringa × hyacinthiflora Hyacinth Lilac single or double depending on cultivar; light blue, pink, lavender, purple; early May, before S. vulgaris; highly fragrant 10 to 12 feet nonsuckering shrub, reddish purple fall color 4
Syringa josikaea Hungarian Lilac single; pink, lilac, rose red; late May to early June 10 to 12 feet shrub; shade tolerant 4
Syringa juliana Julian Lilac single; violet, pink; late May to early June; spicy fragrance 5 feet; horizontal branching low growing shrub 4
Syringa laciniata Cutleaf Lilac single in loose lateral panicles; pale lavender;May; will flower in partial shade; highly fragrant 5 to 6 feet shrub 4
Syringa meyeri Meyer Lilac single; lavender-pink 4 to 8 feet compact, nonsuckering shrub; reddish purple fall color 4
Syringa microphylla Littleleaf Lilac single; rose; highly fragrant 5 to 6 feet compact, broadly spreading shrub 4
Syringa oblata Early Lilac single; white, lavender; late April to early May, one to two weeks before S. vulgaris; some rebloom; highly fragrant 10 to 12 feet shrub; reddish purple fall color 4
Syringa patula Manchurian Lilac single; lavender; highly fragrant 6 to 10 feet compact, nonsuckering shrub; reddish purple fall color 4
Syringa pekinensis Pekin Lilac small, single in large impressive panicles; creamy white 12 to 15 feet multistemmed shrub; attractive bark 4
Syringa × persica Persian Lilac single; white, pale lavender, purplish- red; highly fragrant 6 to 10 feet upright, arching 4
Syringa × prestoniae Preston Lilac single; pale pink to lavender-pink 6 to 10 feet shrub 3
Syringa reflexa Nodding Lilac single; pink with white throat; late May to early June 10 to 12 feet shrub ?5
Syringa reticulata Japanese Tree Lilac single in very large panicles; white; unpleasant fragrance 20 to 30 feet tree; attractive cherry-like bark; fairly shade tolerant 3/4
Syringa villosa Late Lilac single; lavender to pinkish- white 8 to 10 feet nonsuckering shrub; shade tolerant 2
Syringa vulgaris Common Lilac single or double depending on cultivar; many highly fragrant 8 to 20 feet suckering shrub 3
Syringa wolfii Wolf Lilac single; lavender; highly fragrant 20 feet upright shrub to small tree; shade tolerant 4
Lilac Varieties of Note
Syringa vulgaris
`Albert Holden' 7 feet; upright, rounded; deep violet with silvery blush on reverse; zone 2
`Beauty of Moscow' 12 feet; upright; pale pink; zone 3
`Charles Joly' 12 feet; upright; magenta; zone 3
`Charm' 10 feet; rounded; pink; zone 3
`Dappled Dawn' 12 feet; upright, rounded; green and gold variegated foliage; mauve, double; zone 3
`Edith Cavell' 12 feet; upright; white; zone 3
`Ellen Willmott' 10 feet; rounded; white, double; zone 3
`Katherine Havemeyer' 12 feet; upright; lavender-pink, double; zone 3
`Litle Boy Blue' 5 feet; mounded; sky blue; zone 3
`Madame Lemoine' 10 feet; wide spreading; white, double, zone 3
`Marie Frances' 8 feet; upright, rounded; true pink; fragrant; zone 3
`Monge' 12 feet; upright; reddish-purple; zone 3
`President Lincoln' 10 feet; upright; true blue; zone 3
`Primrose' 12 feet; rounded; creamy yellow; zone 3
`Sensation' 10 feet; upright; purple with white edges; zone 3
`Wedgewood Blue' 6 feet; upright; true blue; fragrant; zone 3
Syringa × hyacinthiflora
`Asessippi' 12 feet; upright; pale lavender; fragrant; zone 2
`Blanche Sweet' 10 feet; upright; pale blue tinged with pink; fragrant; zone 2
`Excel' 12 feet; upright; pink; heat tolerant; zone 2
`Maiden's Blush' 6 feet; upright; pink; zone 2
`Mount Baker' 12 feet; upright; white; fragrant; zone 2
`Pochahontas' 12 feet; upright; deep violet; fragrant; zone 2
Syringa × prestoniae
`Audrey' 10 feet; upright; magenta-pink inside nearly white inside; zone 3
`Donald Wyman' 10 feet; upright, dense; reddish-purple; zone 2
`James Macfarlane' 8 feet; upright; true pink; zone 2
`Minuet' 8 feet; compact, dense; distinctive, shiny, leathery foliage; pale pink; zone 2
`Miss Canada' 9 feet; upright, rounded; bright pink; zone 2
Syringa reticulata
`Chantilly Lace' 25 feet; yellow leaf margins; creamy white; leaves may burn in sunny, hot locations
`Ivory Silk' 25 feet; compact, oval; creamy white; attractive, cherry-like bark; zone 4


Using Crabgrass Preventers
Deborah Brown, Extension Horticulturist

crabgrass Crabgrass
Photo credit:
Deb Brown
Crabgrass typically begins to sprout around Memorial Day in the Twin Cities area. It is often a little earlier near "hot spots" such as sidewalks, asphalt drives, and gardens, and this year it might be a little early everywhere. It does not all sprout at the same time, though. Far from it.

Crabgrass will continue to germinate throughout most of the summer, which is why we look for long acting pre-emergence herbicides or crabgrass preventers, and hesitate to put them down too early in spring for fear of limiting their effectiveness later on when we need them.

There is no one magic date after which it makes no sense to use a crabgrass preventer. Even when we begin to see a few little blades of crabgrass sprouting in the garden or in thin areas of the lawn, we can rest assured there are many more seeds in the soil, ready to sprout. Applying the product around mid-May in the metro should still yield reasonably good results; a little further north you have even more time.

Fertilize Lawns Safely
Deborah Brown, Extension Horticulturist

lawns Urban lawn
Photo credit:
Deb Brown
A typical low-maintenance lawn doesn't need to be fertilized at all in spring. But many people like to put down at least one spring application of nutrients. The time to fertilize is when the lawn is growing actively and you've mowed it once or twice.

Some people mistakenly feel that lawn fertilizers are bad for the environment. In fact, when used responsibly, fertilizer actually helps the environment. It allows you to maintain a thick, healthy lawn that is less likely to be invaded by weeds, disease or insect problems. This, ultimately, reduces the need for pesticides.

That healthy lawn not only provides a safe surface for play and recreational activities, it provides "natural air-conditioning", limits the amount of moisture that runs off when it rains, and helps trap particulate matter -- dust, dirt and pollutants -- that settles from the air.

To prevent washing fertilizer into storm sewers, be careful to sweep up any fertilizer granules that fall onto hard surfaces such as your sidewalk or driveway. Water fertilizer into the soil after it's spread, but never apply fertilizer when heavy rains are forecast. Finally, don't rake grass clippings into piles on your drive or street. That's how phosphorus makes its way into our lakes and rivers; it doesn't leach through the soil from fertilizing.

Advice to New Gardeners
Deborah Brown, Extension Horticulturist

sq ft garden Square foot garden
Photo credit:
Deb Brown
More people are gardening every year. We all learn a lot through trial and error or experience, but some errors can be avoided. Here are some tips for novice gardeners to help ensure success.

* Match plants to your site: Most vegetables and flowering annuals need a minimum of 5 or 6 hours of sunlight daily to grow well. If your garden has less than that, or all your sun is in the morning, choose flowers that have some shade-tolerance and skip most of the vegetables. Otherwise flowering will be sparse, plants will stretch, and you'll get little productivity from vegetables and root crops.

* Go easy on the fertilizer (unless you garden in sandy soil, which needs to be fertilized more frequently): Work plenty of organic matter such as leaf compost, peat moss, or well-rotted, (old) manure into the soil to help hold water and nutrients. Add small amounts of fertilizer such as 5-10-10 or 10-10-10 to the soil before you plant and again in July. Chances are, that's all you'll need. Too much fertilizer increases leafy, vegetative growth, often at the expense of flowering and fruit production.

* Plant in blocks rather than rows: Unless your garden is quite large and you plan to run a rototiller between rows, it's more efficient -- and in the case of flowers, more attractive -- to plant in groups. Put those that will grow tallest on the north end of the garden so they don't shade others as the sun moves from east to west.

* Don't bite off more than you can chew: Enthusiasm has been known to wane as temperatures soar, weeds multiply and mosquitoes take their toll. Even those lovely hanging baskets lose some of their appeal when you have to water them once or twice daily! Start with a small, manageable garden and let your growing interest in this fascinating and rewarding hobby determine how much you want to expand each year.

Moving Houseplants Outdoors for Summer
Deborah Brown, Extension Horticulturist

houseplants Houseplants outdoors
Photo credit:
Deb Brown
Many houseplants benefit from additional light they receive spending the summer outdoors. Place them in a protected location under a tree or on the north side of a building. That way they'll only be exposed to filtered light or to direct sunlight early or late in the day when it won't burn them. They'll receive enough reflected light, however, to support lots of healthy new growth.

Wait to move houseplants outdoors until all danger of frost has passed and night temperatures have warmed into the mid-50's. The warmer and windier the weather, the more often you must water them, even in a sheltered location. Plan to fertilize every three or four weeks, with fertilizer diluted to half the label-recommended strength. Fertilize more often if growth is rapid and foliage doesn't appear as green as you feel it should be.

Large-leaved houseplants will probably fare better in a sunny porch than outdoors, exposed to the elements. They could be ripped to shreds by pounding rain and hail. And if they're good-sized, attractive plants, they may prove too tempting to strangers passing by.

Rings Around the Lawn:
Chad Behrendt, Plant Pathologist

Necrotic Ring Spot
ring spot1
ring spot2 Necrotic ring spot
Recently the Yard and Garden Clinic has received several lawn samples with necrotic ring spot. This early and late season turf grass disease is most frequently observed on sodded lawns, which are 2 to 4 years old. Symptoms typically appear as a circular patch or ring of dead, sunken grass. Multiple infections may cause a decline or dieback of the entire lawn.

Initially, necrotic ring spot appears as a light green spot. As the disease progresses the fungus attacks the root system, killing the grass plants. As plants die, a reddish-brown to straw colored patch appears. These sunken patches often retain a green center giving the patch a ring-like appearance. The healthy grass growing in the center of the ring has either survived the infection or reestablished itself in the center of the dead patch. Rings are usually no larger than one foot in diameter, but may coalesce to form a large diffuse patch, with green circular clumps of grass.

Although necrotic ring spot is an early and late season disease, it can persist throughout the growing season. Symptoms usually begin to develop during the early or later part of the season; however, rings from earlier infections may be visible in the home lawn anytime during the growing season.

Necrotic ring spot, like other turf diseases, is promoted by stressful conditions. Management should begin with properly watering, fertilizing, and mowing. Manage the thatch layer so that it does not exceed ½" by dethatching and aerating the soil. Soil aeration also benefits the home lawn by increasing microbial activity, water infiltration, and reducing soil compaction. Finally, severe cases may require a fungicide application. The fungicide thiophanate-methyl should be applied when the soil temperature, at a depth of 2", reaches 65° F.

Fairy Rings
Fairy Ring Fairy Ring Spot
Photo credit: U of M Plant Disease Clinic
A second type of ring disease that you may observe in your lawn this spring and summer is fairy rings. Fairy rings may appear as dark green rings of grass in moist soils, rings of mushrooms, or as a series of concentric rings and mushrooms. Concentric rings usually contain a dark green outer ring surrounding a brown necrotic ring and a dark green center. These rings may reach a size of 15 to 30 feet. This disease, when young, may mimic necrotic ring spot. However, fairy rings are usually much larger, and often contain mushrooms.

Unlike necrotic ring spot, fairy rings are decomposers, which utilize organic litter in the thatch and soil layers. Fairy rings are promoted by an excessive thatch layer and drought stress. As the fungus progresses outward, it decomposes organic matter, inhibits or kills grass plants, and provides nutrients to the adjacent turf. This causes the typical concentric ring pattern.

To manage fairy rings properly water, mulch, and fertilize the lawn. Fungicides are not effective against fairy rings. In addition, remove any large pieces of organic matter such as old stumps remaining in the soil, and manage the thatch layer so it does not exceed ½". To remove small infections, you may try to dig out the infected soil and replace it. However, this is not usually effective or feasible.

The Proof is in the Picture!
Chad Behrendt, Plant Pathologist

2spruce

spruce Two spruce (top)
Cytospora canker on spruce (bottom)
Photo credit: Chad Behrendt
They say a picture is worth a thousand words. Well, this one is worth the price of a native spruce tree such as white spruce, its variant Black Hills spruce, or Norway spruce. As you can see, the Colorado blue spruce tree on the left is losing all of the needles on its lower branches, while the native white spruce (right) is completely healthy. The disease causing needle loss in this picture is Cytospora canker.

Cytospora canker, caused by the fungus Cytospora kunzei, is a common disease of all spruce trees in Minnesota. Trees suffering from drought or other environmental stresses are more susceptible to Cytospora canker, while healthy vigorous trees are more resistant. Native spruce trees tend to be tolerant of environmental stresses, while the non-native Colorado blue spruce suffers from a variety of environmental stresses. As a result, native spruce are usually highly resistant to Cytospora canker, while Colorado blue spruce, predisposed by environmental stress, is highly susceptible to infection by Cytospora canker. In addition, Colorado blue spruce is more susceptible to the fungal needle disease Rhizosphaera needle cast, than native spruce trees.

Cytospora canker initially infects lower branches near the base of the tree. Symptoms include elliptical or diamond shaped cankers, heavy resin exudation, and branch dieback. As resin dries on the branch it appears whitish or gray in color. Needles on infected branches fade, turn brown, and fall from the tree the winter following infection.

To manage trees with Cytospora canker increase tree vigor and properly prune dead or dying branches. There are no chemicals available for controlling Cytospora canker.

Rain Drops Keep Splashing All the Spores...
Chad Behrendt, Plant Pathologist

Due to recent rains, springtime diseases such as ash anthracnose, apple scab, cedar apple rust, and powdery mildew may begin to appear in the home landscape. These diseases are stimulated by wet periods and require water for germination, growth, and reproduction. In addition, rainfall helps disperse spores from infected tissues to healthy tissue by splashing spores. Therefore, keep an eye out for spring diseases and be prepared to manage them properly.

Dieback of Dogwood
Chad Behrendt, Plant Pathologist

dogwoodcanker Dogwood canker
Photo credit: Chad Behrendt
Almost every year the clinic receives calls on dying dogwoods. Dead branches and dieback are common symptoms, but identification and diagnosis is difficult. A variety of environmental and fungal problems may cause stem and branch dieback including winter injury, insects, animal chewing, and fungal cankers.

As usual, the clinic received a cankered dogwood sample this spring. The cankers appeared to be fungal in nature and were highly associated with branches or lenticels. These cankers were best described as slightly raised, gray, patches with small black dots in the center of the patch. In addition, several smaller branches were completely girdled and killed. Cankers on these branches progressed downward from the smaller branch to the main stem.

After a close examination, spores were observed in the black dots. Although a positive identification was not made, these spores and pycnidia were symptomatic of Sphaeropsis species, a common canker on dogwood.

To control cankers on dogwood prune infected branches and destroy during dry weather. Sterilize pruning tools between cuts in a 10% bleach solution. To maintain vigor and health, mulch, and fertilize the plant.

It's Time to Spray for Rhizosphaera Needle Cast
Chad Behrendt, Plant Pathologist

rhizosphaera needle
Rhizosphaera on needles
Photo: U of MN Department of Plant Pathology
Rhizosphaera needle cast, a very common disease of spruce trees, can cause extreme damage to the lower branches of Colorado blue spruce. Needle loss is usually noticed as the inner needles on the lower branches begin to fall. The disease then progresses from the base of the tree upward and from the trunk outward. Black fungal structures called pycnidia, which appear as black dots in the white stomata of the needle, are a diagnostic sign of this disease.

If your trees have Rhizosphaera needle cast you should be prepared to put on the first fungicide application. Chlorothalonil, Daconil 2787 or Bravo, should be applied when the new growth is half elongated (approximately ½" to 2" in length). A second application should be applied 3 to 4 weeks later. Currently, most spruce trees in the Twin Cities area have approximately ½" of new growth.

Test your diagnostic savvy monthly at Disease Watch at: http://www.extension.umn.edu/projects/yardandgarden/Plpa.htm

Editorial Notes

Thank you for reading this third issue of the Yard & Garden Line News. The back issues are now on the newly revised Yard & Garden Line home page at www.extension.umn.edu/projects/yardandgarden/. The new home page has clickable links to most of the components of the Yard & Garden Line, such as Bell Museum of Natural History, Yard & Garden Clinic, 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. Plant Health Care Update is a newsletter written by Master Gardeners for Master Gardeners. The authors have completed advanced training to earn the designation Plant Health Care Advisors.

If you have gardening questions, please call the Yard & Garden Line at (612) 624-4771 in the TC metro or 1 (888) 624-4771, toll free, in Greater Minnesota.

diagnostic

Introducing: Yard and Garden Clinic's new logo! While preparing a promotional mailing to garden centers earlier this month, it became clear that the Yard & Garden Clinic's identity had been blurred with that of the Yard & Garden Line. So, to keep it distinct, we asked Adam Turman, our graphic artist, create a "diagnosing"daisy. She has her magnifying glass at hand to ferret out the identity of plants and the cause of plant problems. She makes her public debut here, at left.

In upcoming issues, our guest authors will be writing about using lime and gypsum in garden soils, using manures in garden soils, low maintenance grass mixes and care and maintenance of marginal hardy trees and shrubs. Watch for them! If you have suggestions for other topics, please let me know!

We publish the Yard & Garden Line News twice a month during the gardening season, on the 1st of the month and the 15th of the month.

For plant and insect questions, visit http://www.extension.umn.edu/askmg. Thousands of questions have been answered, so try the search option in the black bar at the top left of the board for the fastest answer.

If you would like to receive an e-mail reminder when the next issue of the Yard & Garden Line News is posted to the web, just send an e-mail to: listserv@lists.umn.edu (note: the second E in listserve is omitted), leave the subject line blank, then in the body of the message, type: sub yglnewslist or to unsubscribe, enter: unsub yglnewslist

Happy gardening!

Beth Jarvis
Yard & Garden Line Project Coordinator

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