Yard & Garden Line News Volume 4 Number 7                                                               May 15, 2002

Features this issue: What Happens When Trees are Defoliated? Plant Raspberries for a Home-grown Treat Pulling out the Big Guns: Fungicides for Disease Management in the Home Landscape Pennsylvania Wood Cockroach Expect High Numbers of Forest Tent Caterpillar Mystery ‘Worms' Check Out the Insect Galleries Editorial Notes

What Happens When Trees are Defoliated?
Patrick Weicherding, Extension Educator-Horticulture, Anoka Co.

Whitemarked tussock moth caterpillar feeding damage. Photo: Ent. Dept.

Deciduous trees defoliated by insects are rarely killed. Evergreen trees, on the other hand, are frequently killed by one severe defoliation. As a rule of thumb, a healthy deciduous tree can tolerate three consecutive years of severe defoliation before it is killed.

Trees defoliated by insects early in the growing season will produce new leaves in July after feeding has ended which helps the tree recover. However, defoliation does decrease the energy reserves of the tree, reducing its ability to resist disease and insect pests to which it is normally resistant.

Furthermore, defoliated trees are also much more susceptible to the damaging effects of drought. Trees previously weakened by transplanting, drought stress, construction damage or other abiotic factors may be killed by defoliation.

Plant Raspberries for a Home-grown Treat
Deborah Brown, Extension Horticulturist

'Redwing'--ready to pick. Photo credit: U of MN Ext. Svc.

Our slow, cool spring means there's plenty of time to plant trees and shrubs in your landscape. If you've got a sunny location with well-drained soil, consider growing raspberry bushes in your own yard. The plants are not very demanding. Red raspberries are perfectly hardy here, and they produce lots of fruit when planted in a good location and given a modest amount of care.

You needn't get into fruit growing in a big way to enjoy raspberries. As few as four or five well-tended bushes will yield plenty of berries to sprinkle on your cereal or ice cream for several weeks each summer, and perhaps again in autumn if you plant one of the ever-bearing (also called fall-bearing) varieties.

Raspberry plants aren't particularly fussy about the type of soil they grow in, as long as water doesn't puddle there. (Poorly-drained soil encourages root rot, or at the very least, poor root growth.) If your soil is quite sandy, however, it would be a good idea to incorporate lots of baled (dry) peat, compost, or other organic matter into it before planting, to help maintain moisture and nutrients. Without adequate moisture, your berries will be smaller and less juicy.

Before you plant, be sure to get rid of weeds, especially perennials such quackgrass or creeping charlie. Use a non-selective herbicide such as glyphosate (sold as RoundUp) that allows you to plant within days of application. The job will be much more difficult once the raspberries are in, because most herbicides that kill tough, perennial weeds will also kill your raspberry canes.

Plant red raspberry bushes two to three feet apart. If you put in more than one row, space the rows at least six feet apart. Allow new canes to fill in, but leave only four or five sturdy canes per foot of row, to avoid ending up with a miserable "bramble patch" that's only marginally productive. When you allow too many canes to develop they'll compete for available water and nutrients. Air circulation will also be reduced, so leaves dry more slowly after rainfall, giving fungal diseases a better opportunity to develop.

Fertilize newly planted raspberries by working 1/4 cup of high nitrogen fertilizer into the soil around each plant. In following years, use about 1/2 cup of 10-10-10 per plant, early each spring. If you prefer an organic approach, fertilize with well-composted manure before you plant, and again every following spring. Incorporate the manure at the rate of 3 1/2 cubic feet per 100 square feet.

Fresh raspberries. Photo credit: U of MN Ext. Svc.

It's a good idea to mulch your raspberries with several inches of wood chips, grass clippings or shredded leaves. Mulch helps retain soil moisture and blocks the light that's needed by many weed seeds to germinate.

Plan on watering during any dry weather from spring right through the completion of fruit harvest. These plants need a total of 1 to 1 1/2 inches of water every week (in the form of rainfall or irrigation) to ensure the growth of plump, juicy berries.

Canes of ever-bearing varieties produce fruit their first year in fall, then a second time the following summer. Canes of summer-bearing varieties don't produce fruit at all their first year, only the second. Regardless of which type raspberries you plant, prune all canes that have produced fruit in June or July smack down to the ground right after you've harvested the last few berries. Individual canes that fruit in early summer will never bloom and fruit again. New canes will arise from the roots to take their place, however.

There are many good summer-bearing raspberry cultivars available. ‘Boyne', ‘Festival', ‘Liberty' and ‘Killarney' are hardy throughout the state; ‘Newburgh', ‘Haida' and ‘Sentry' are only suited to the southern third. Ever-bearing varieties ‘Fallred', ‘Redwing', ‘Summitt', ‘Fallgold' (a yellow variety) and ‘Autumn Bliss' are hardy border to border, though early cold weather may eliminate their fall crop in northern regions.

Pulling out the Big Guns: Fungicides for Disease Management in the Home Landscape
Janna Beckerman, Extension Plant Pathologist

Filipendula sp. coated in PM. Photo credit: Beth  Jarvis

Integrated Pest Management (IPM) is quite simply sound growing practices. These practices involve carefully choosing plants to match your site and providing the right conditions for them, checking them regularly (scouting), and intervening when pest or disease damage reaches unacceptable levels. Often times, many of these problems could have been minimized or even prevented by utilizing resistant varieties, or by planting plants in the appropriate site. All of these approaches work to reduce disease pressures. Quite simply, healthy plants require fewer pesticides.

However, at some point in time, you will be confronted with a problem that cannot be managed non-chemically, or has reached a level of disease that is no longer tolerable to you. Keep in mind that deciding to use fungicides does not mean that all other management strategies can be abandoned. Fungicides are one component, but not the only component of good disease management. Research your fungicides before use: Most fungicides are preventatives and many are specific to the control of only a few diseases. This means that you must correctly diagnose the disease, identify the proper fungicide and then correctly time fungicide application. Your goal is to apply the fungicide before the fungus enters the plant to prevent infection and disease development. "Spraying and praying" is not good disease management practice! Even with good fungicide use, prevention-not cure-is the name of the game.

Although many fungicides are registered for use on plants by nursery professionals, few are readily available to home gardeners. This may be hard to believe when confronted with numerous bottles, all of which are claiming to be the best fungicide for the job! Whenever deciding on a fungicide, carefully examine the active ingredient. You will notice that many companies package the same fungicide, but under different names. Homeowners looking to purchase a fungicide with the active ingredient chlorothalonil will find it packaged as Bravado, Daconil 2787, Funginil, or Multi-Purpose Fungicide, all of which contain 29.6% of the active ingredient, chlorothalonil. Usually, higher concentration fungicides command higher prices for the same formulation and aren't available to home consumers. At this point, you may also notice that some fungicides are in bottles designed for pouring, spraying or sprinkling the product. The differences in concentration are often due to the differences in formulation. Fungicides are available as liquids, dusts, granular mixes, wettable powders, and emulsifiable concentrates. Liquids that are easily sprayed on foliage usually contain lower concentrations of fungicides than their granular counterparts, because the fungicide is directly in contact with the pathogen. The ingredient list on the label will tell you what is in the product and any adjuvants designed to help the product stick to the plant. Always read the label with care-some fungicides will list which plants should not be treated due to toxic reactions with that plant!

In many past issue of Y & GL News, Chad Behrendt and I have highlighted common diseases and discussed the disease life cycles. Understanding the disease cycles and knowing when spores are released allows you to properly time fungicide use. Most fungicides are preventatives, so knowing when the spores are released allows you to time your fungicide application in a way that targets your disease problem.

Below is a list of commonly available home fungicides. Fungicides in bold are considered "organic." PM=Powdery mildew When choosing a fungicide, remember: The label is the law. Read the entire label and follow the directions. Examine the label carefully to make sure the plant you are about to spray has been labeled as an acceptable host with that fungicide. Some fungicides will produce phytotoxic (plant poisonous) interactions that can debilitate or kill the plant. For example, sulfur causes injury and defoliation to cucumbers, melons, spinach, squash and viburnum.

When using a fungicide, remember to use them with caution and not with fear. The fungicides listed below have low toxicity when compared to insecticides and nematicides. When using fungicides, remember to apply them when the weather is calm and risk of rain is minimal. Be sure to clean all equipment and then yourself and your clothing after application.

Finally, remember that many diseases can be controlled using several non-chemical control techniques outlined in the previous edition of Yard and Garden News. When managing any disease problem, a combination of both cultural and chemical techniques usually works quite well for control of most diseases.

Table 1. Fungicides available for home use.

Common Name	Trade Name(s)	Uses/Mechanism	Comments
Aluminum tris	Aliette	Foliar / Protectant and Systemic Drench	For control of downy mildews, phytophthora and pythium diseases.
Captan	Captan Garden Fungicide	Foliar / Protectant Seed Drench	general-purpose fungicides for numerous plant diseases Not effective against PM and rusts
Chlorothalonil	Daconil 2787, Multipurpose Fungicide, Bonomyl, Funginil	Foliar / Protectant	general-purpose fungicides for numerous plant diseases. Discoloration of blooms may occur on some flowers, especially roses
Copper	Bordeaux Mixture, Kocide, Fixed Copper Liqui-Cop	Foliar / Protectant	Most readily available to gardeners, it controls fungal and bacterial disease. Can cause burn if applied too early or under cool conditions
Horticultural Oil	Stylet Oil, Saf-T-Side Spray Oil, Sunspray Ultra-Fine Spray Oil Plant-based oils include neem oil (e.g., Powdery Mildew Killer) or jojoba oil (e.g., E-rase)	Foliar /Protectant	Excellent control for PM Never apply oil within 2 weeks of a sulfur spray to prevent plant injury. Do not apply oil when temperatures are above 90°F or to drought-stressed plants.
Lime Sulfur	Polysul, Liquid sulfur, Flower and Vegetable Dust,	Foliar / Protectant	Labeled for PM, scab, brown rot, and rusts on ornamentals. Can cause burns if applied to young leaves/ shoots or in hot weather.
Mancozeb	Mancozeb, Dithane, Fore	Foliar/ Protectant	Broad spectrum foliar fungicide for control of leaf spots, blights.
Maneb	Maneb Lawn and Garden Fungicide	Foliar / Protectant	Broad spectrum foliar fungicide for anthracnose, leaf spots, early and late blight
Myclobutanil	Spectracide, Immunox, Systhane WSP	Foliar/ Systemic	Controls powdery mildew, anthracnose black spot of rose, fungal leaf spots, and rusts.
Salts of Bicarbonate	First Step, Kaligreen	Foliar / Protectant	More effective when used in combination with oil.
Sulfur	Safer’s Garden Fungicide, Sulfur 90W	Foliar / Protectant	Elemental sulfur is effective against PM, leaf blights, rusts, and fruit rots. Can burn young tissue.
Thiophanate-methyl	Halt, Cleary’s 3336	Foliar/ Systemic, Contact,	Effective control of PM, leaf spots and blights, rust and scab.
Triadimefon	Bayleton, Fungi-Fighter	Foliar/ Systemic	For control of rose diseases, PM, rusts and tip blights.
Funginex, Orthinex, Triforine	RosePride Rose & Shrub Disease Control	Foliar / Protectant, Systemic, Contact and Curative	Used for control PM, leaf spots and rusts of over 20 ornamentals

Test your diagnostic savvy monthly with Disease Watch at: http://www.extension.umn.edu/projects/yardandgarden/PlantPathWeb/Plpa.htm
Pennsylvania Wood Cockroach
Jeff Hahn, Assistant Extension Entomologist

Left: Male, right: female top: nymph Photo credit: Jeff Hahn

One day, you are walking around your house when you see what looks like a cockroach. You see a few more over the next couple of days. Since that is not an insect you want to have in your home, you look more closely to be sure what it is. The insect seems to move quickly, has strong, stout legs covered with spines, long antennae, and its head that isn't visible from above. Yeah, that looks like a cockroach. Better get some bait to deal with them or get a professional pest control service to treat them.

But wait a minute. While most cockroaches, like the German cockroach, are considered to be household pests, not all species are. An exception to this would be the Pennsylvania wood cockroach. This is an outdoor species that typically lives in wooded areas where they feed on decaying vegetation. It occasionally enters homes and other buildings but it can not become established indoors. It is essentially like a boxelder bug or a cluster fly that invades homes but is no more than a nuisance.

You can usually distinguish a Pennsylvania wood cockroach from other cockroaches without too much problem. An adult male has long wings, is about 1 inch long, is chestnut brown with a light colored margin on its body near its head. It is also attracted to lights and is a good flier. The female is a little smaller, about 1/2 - 3/4 inch long, with short wings that expose part of the abdomen. Like the male, the female has light colored margins near it head.

The immature Pennsylvania wood cockroach nymph may not as easily recognized. It is sometimes confused with the Oriental cockroach. The Pennsylvania wood cockroach nymph is dark colored, and wingless. Like adults, light colored margins are present. However, this margin can be indistinct and difficult to see. People may find nymphs in their home periodically during winter. They are more likely to encounter them in the spring as the weather warms up, especially when the building is associated with a wooded area.

An Oriental cockroach adult is also dark colored and wingless but it never has light colored margins. It is not associated with wooded areas but with cool, dark sites in buildings -- it is typically found in damp basements, crawl spaces, and sewers. If it is not possible to distinguish between these two species based on color and where they are found, then it is necessary to look at additional characteristics. This requires a close examination of specimens, looking for a pattern of spines on the hind legs and the shape of the anal plate to verify which species is present. This is something best left to a specialist.

Physical removal is usually the only the necessary control for a Pennsylvania wood cockroach. If cockroaches are persistently entering your home, you can reduce their numbers by removing any wood piles and accumulations of leaves and other vegetation near the home. Also caulk or seal any obvious cracks or spaces to help keep insects out. Males are attracted to lights so keep outside lights turned off or switch to less attractive yellow lights.

Expect High Numbers of Forest Tent Caterpillar
Jeff Hahn, Assistant Extension Entomologist

Forest tent caterpillar. Photo credit: Dept. of Entomology

We have endured high numbers of forest tent caterpillars throughout much of the northern and central areas of Minnesota the last several years. This problem is not over yet as we are expecting another outbreak year of these insects. But the end may be in sight as this could be the last big season before forest tent caterpillar numbers start to dramatically go down. Forest tent caterpillars maintain outbreak populations for about 3 - 4 years. After that their populations crash. It will be about 8 - 13 years before their populations cycle to high numbers again.

Forest tent caterpillars hatch sometime in the spring. They love aspen, as well as birch, basswood, oak, ash, and many other deciduous hardwood trees. However, you will rarely find them feeding on red maples and pine, spruce, and other conifers. They feed for about 5 - 6 weeks before pupating. Adults emerge in mid-July and lay eggs which remain until the following spring. There is one generation each year.

When populations are high, trees are often severely defoliated. Healthy, vigorously growing trees can tolerate even complete defoliation in two or three years consecutive years without serious injury. However, during an outbreak (four consecutive years or more of severe defoliation), moderate or severe defoliation can reduce growth, cause branch dieback, or possibly even kill trees. Young or unhealthy trees are less tolerant of severe defoliation in a single season.

The sheer numbers of this insect makes it very difficult to protect trees from them. This is particularly true when a large area is involved. These insects should be tolerated and ignored whenever possible. If it is deemed important to protect a wood lot or landscape trees, it is very important to treat the caterpillars when they are small, i.e. one inch long or less. This will require watching trees closely for emerging caterpillars. They can hatch as soon as early May but because of our cool spring, they will most likely emerge closer to mid May.

There are many residual insecticides for treating forest tent caterpillars. Less toxic products effective against caterpillars, especially small, young ones, are Bacillus thuringiensis var. kurstaki, insecticidal soap, spinosad (e.g. Conserve), azadirachtin (e.g. Azatin, BioNeem). If you wish to protect a large area, it is most effective to hire an aerial applicator to treat it. Landscape trees, especially if they are large, may require the services of a professional tree care company to spray it.

Mystery ‘Worms'
Jeff Hahn, Assistant Extension Entomologist

March fly larva. Photo credit: Jeff Hahn

Some people have been concerned about large numbers of unusual looking ‘worms' they have discovered under leaves or compost piles in their yard. The insects in question are march fly larvae, belonging to the family Bibionidae. They are generally dark-colored and grow to be about 1 inch long. They have a conspicuous head but lack legs. They also possess short spine-like setae (hair-like structures) over much of their body.

March fly larvae feed on decaying organic debris and often are quite numerous. They are typically found in the soil under leaves, manure, and other areas of high organic matter. They also can be found in grassy pastures and meadows and on forest floors. While there are also records of march fly larvae feeding on the roots of grass, that is rarely, if ever, seen in Minnesota. It isn't necessary to manage march fly numbers in your garden. Just ignore them.

Check Out the Insect Galleries
Jeff Hahn, Assistant Extension Entomologist

The insect gallery pages, http://www.extension.umn.edu/projects/yardandgarden/EntWeb/galleries/galleries.html, has been recently revised. The format has changed from four to three major headings: Outdoor Insects, Indoors Insects, and Medically Important Arthropods. Indoor Insects and Medically Important Arthropods are finished. We are continuing our work with Outdoor Insects and plan to have additional updates completed this spring. Please check back periodically to see our progress.

Get the low down on this month's insect pests at Insects http://www.extension.umn.edu/projects/yardandgarden/EntWeb/Ent.htm
Editorial Notes

Pasque flower Pulsatilla patens Photo credit:  Beth Jarvis

The pasque flower is blooming in my back yard. It's a native prairie plant that is classified as being of the mesic prairie. Mesic means neither wet nor dry. Obviously, it's one of the early blooming perennials, as it's beaten out only by the super-early bulbs and is now blooming with tulips, daffodills, trillium and other woodland ephemerals. I've seen it in a rock garden and mine's in a raised "holding" bed (where it's been parked for 2 years).

We're clearly ahead of the game on rainfall for May. Apples and lilacs are usually in bloom for Mother's Day and that didn't happen this year. Looks like it will take a week or so before the apples and lilacs on campus are in full bloom.

Please feel free to cut and paste any of the articles for use in your own newsletters. All we ask is that you give our authors credit.

Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/yardandgarden/. Our 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.

Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Thursday of every month at 10 a.m. Katherine Lanpher hosts the program that is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations.

If you have gardening questions, please call the Yard & Garden Line at (612) 624-4771.

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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