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November 2010 Archives

Contents: November 1, 2010

In this issue of the Yard and Garden News:

  • The Plight of Bees

  • Help your woody ornamentals survive the coming winter

  • Pollinator blues: part II

  • Beware of bed bug internet hoax

  • Rust diseases of lawn grasses very common this fall

  • Prevent snow mold on lawns now

The Plight of Bees

Marla Spivak (University of Minnesota); Eric Mader and Mace Vaughan (Xerces Society for Invertebrate Conservation); Ned Euliss (USGS)
Excerpted from feature article to appear in upcoming issue of Environmental Science and Technology.

Bee Declines

Colony collapse disorder (CCD), the name for the syndrome causing honey bees to suddenly and mysteriously disappear from their hives--thousands of individual worker bees literally flying off to die--captured public consciousness when it was first named in 2007. Since then, the story of vanishing honey bees has become ubiquitous in popular consciousness--driving everything from ice cream marketing campaigns to plots for The Simpsons. The untold story is that these hive losses are simply a capstone to more than a half-century of more prosaic day-to-day losses that beekeepers already faced from parasites, diseases, poor nutrition, and pesticide poisoning.

The larger story still is that while honey bees are charismatic and important to agriculture, other important bees are also suffering, and in some cases their fates are far worse. These other bees are a subset of the roughly 4,000 species of wild bumble bees (Bombus), leafcutter bees (Megachile), and others that are native to North America. While the honey bee was originally imported from Europe by colonists in the early 17th century, these native bees have evolved with our local ecosystems, and along with honey bees, are valuable crop pollinators.

People want to know why bees are dying and how to help them. This concern provides a good opportunity to more closely examine pollinators and our dependence upon them. Bees are reaching their tipping point because they are expected to perform in an increasingly inhospitable world.

Bee declines can be attributed to three factors:

1. Bees have their own diseases and parasites that weaken and kill them. Sick bees are more susceptible to the effects of poor nutrition and pesticide poisoning, and vice versa.
2. Many flowers, nest sites, and nesting materials are contaminated with pesticides. Bees pick up the insecticides, herbicides and fungicides applied to home gardens and lawns, golf courses, roadsides, and crops. These pesticides, alone and in combination, can be toxic.
3. There are not enough blooming flowers over the length of the growing season in our agricultural and urban landscapes to support bees.

Emerging Responses to Declines in Bee Health

To study CCD and other pollinator health issues, the 2008 Farm Bill approved more than $17 million in funding annually for five years for the U.S. Department of Agriculture (USDA) and for university research grants. The Farm Bill also approved another annual $2.75 million for five years to increase honey bee health inspections. Since the Farm Bill became law this funding has never been fully appropriated.

The 2008 Farm Bill also dictated that current USDA competitive grant programs should include pollinators - honey bees and native bees - as research priorities. As a result, research programs funded by the USDA under the National Institute of Food and Agriculture (NIFA), such as the Specialty Crops Research Initiative (SCRI) and the Agriculture and Food Research Initiative (AFRI), made pollinators a research priority in 2010.

Protection from Pesticides

A factor that can be addressed at multiple levels is the use of pesticides. In particular, while extensive literature exists on the sublethal effects of insecticides on bees in the laboratory, little exists on sublethal effects to colonies under natural conditions. Common insecticides such as neonicotinoids and pyrethroids have been shown to affect learning, foraging activities, and nest site orientation by honey bees at sublethal doses.

Individual farmers and homeowners have the ability to mitigate harm to pollinators through simple changes in application methods such as avoiding treatments around blooming plants or to areas where bees are nesting. Evening spraying when bees are less active is another simple, underutilized way to reduce harm. The best course of action, and the one most accessible to gardeners, for whom insect damage is cosmetic rather than economic, is to eliminate the use of pesticides entirely.

The Need for Habitat

The third major challenge facing bees is a lack of season-long food sources, especially in agricultural landscapes where, if bee-pollinated plants even exist, they typically consist of large monocultures like cranberries, canola, or almonds, which provide only a few weeks of abundant food followed by a season-long dearth. Roughly 360 million hectares, or more than one-third, of the lower 48 states are managed as private cropland, pasture, or rangeland. This makes agriculture the largest land use activity in the country and thus one with the most potential impact on bees.

Specific habitat guidelines for all of these landscapes (rural, urban, roadside) vary across regions. Baseline habitat guidelines encourage the inclusion of at least 3 different plant species that bloom at any given time during the growing season (spring, summer, fall), with more being even better. For planting recommendations, visit:

Concluding Remarks

Pollinators are receiving more conservation attention today than at any other time in history. Scientists, conservationists, and farmers are working harder than ever - in partnership - to understand how pesticides, diseases, and habitat loss impact pollinator populations. They are also working to understand the most successful strategies for creating landscapes that support the greatest abundance of these important insects.

At the same time, the public and policy-makers are increasingly aware of the problems afflicting bees and the critical role they play in food production and natural systems. But there is no reason to wait for research and policy to mitigate the plight of the bees. Individuals can modify their immediate landscapes to make them healthier for bees, whether that landscape is a public rangeland in Wyoming or a flower box in Brooklyn. It is also possible to reduce agricultural and urban pesticide use to mitigate bee poisonings. We can engage in the sustainable management of honey bees and native bees. Promoting the health of bee pollinators can begin as an individual or local endeavor, but collectively has the far-reaching potential to beautify and benefit our environment in vital and tangible ways.

Editor's note: Imadicloprid we have been talking about is a neonicotinoid.

Pollinator Blues: Part II

Karl Foord, UMN Extension Educator

Pollinator Blues - Part II

To approach the problem of creating a bee friendly garden,I first researched the plants that are pollinator friendly and created a table of pollinator friendly plants from the Xerces site (Exhibit 1).

Second, I used the following recommendations from the Urban Bee Garden site as criteria for selecting plants; the goal being to insure that continual bee floral food will be available for the complete growing season.

1. Plant a minimum of three plant species that bloom at any given time during the growing season i.e. spring, summer and fall.

2. Each species of flower should be planted to a minimum patch size of approximately 5 ft. x 5 ft. Patch size is important because smaller patch sizes will often be ignored, even if the plant is quite attractive to the bees.

3. Higher bee diversity and abundance occurs when gardens have a rich assortment of bee plants. It also appears that bees remain longer in a garden if plant diversity is high.

Third, I then took an inventory of my present plants and estimated their flowering periods (shown in yellow on Exhibit 2). Fourth, I considered the areas available for planting shown in my property. Given the patch size and species diversity recommendations, I chose six plants to fortify my local bee garden, as follows: Milkweed (Asclepias), Single flowering Roses (Rosa), Catmint (Nepeta), Russian sage (Perovskia), Cosmos (Cosmos), and Lavender (Lavandula). These plants were chosen for attractiveness to bees and longer flowering periods.

I hope that you will consider increasing the attractiveness of your plantings to bees, if appropriate. Taking an inventory of the flowering periods and bee appeal of the plants that you presently have is a good first step. Then choosing plants from the table to supplement, if necessary, should enable you to increase the appeal of your bee garden.



Help Your Woody Ornamentals Survive the Coming Winter

Kathy Zuzek, UMN Extension Educator

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Photo 1: Winter burn symptoms. Kathy Zuzek, UMN Extension.

The effects of winter sun, wind, temperature fluctuations, snow, and ice can all combine to make winter a high-hazard time for tree and shrub health. Animal browsing is an additional challenge in our winter landscapes. Here's a checklist for gardeners who want to minimize injury to woody ornamentals in the coming winter.

Apply tree wraps and tree guards to prevent sunscald. Sunscald occurs when winter sun heats up bark on the south or west side of a tree enough to stimulate cambial activity. When shading or sunset causes the air temperature to drop quickly, the activated cambium is killed resulting in dead bark on the south or west side of a tree in the form of sunken, dried, or cracked areas. To prevent sunscald, tree wraps and guards should be applied in fall. They should be light-colored to reflect sun and to keep bark at a lower temperature on sunny winter days. Pay special attention to trees that have bark newly exposed to sun from recent pruning to raise tree canopies, trees that have been recently transplanted from shady sites to sunny sites, and young trees and other thin-barked trees such as cherries, crabapples, plums, maples, mountain ash, basswood, and honey locust. You will need to protect newly planted and thin-barked trees for several years but remember to remove tree wraps each spring and reapply them in autumn.

Avoid over watering and late season fertilizing that can encourage late season succulent growth. Late season growth is vulnerable to winter injury.

Avoid under watering of your trees and shrubs. Remember to water trees and shrubs in your landscape until the ground freezes. As temperatures drop in autumn and plants are acclimating for winter, it is easy to forget that they still need water. Inadequate watering stresses plants. Avoid this stress by watering until the ground freezes. The average freeze date of soils in Minnesota ranges from mid-November through mid-December; the average date for Minneapolis and St. Paul is December 6.

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Photo 2: A burlap barrier to prevent winter burn. Kathy Zuzek, UMN Extension.

Roots are less hardy than stems of woody plants and can be injured when soil temperatures reach 10-15 ° F. Thankfully, soil temperatures are much higher than air temperatures in winter. A moist soil holds more heat than dry soil and helps to prevent deep frost penetration.

Evergreen foliage that turns brown during winter due to desiccation and injury is called winter burn (Photo 1). One way this damage occurs is when winter sun and wind trigger transpiration in evergreen foliage. During transpiration stomata (the openings on foliage that allow gas and water exchange with the atmosphere) open and water is lost from the foliage. Because the soil is frozen, the plant cannot replace the lost water and foliage desiccates and turns brown. Damage often occurs on the south, southwest, or windward side of evergreens but in severe cases, an entire plant can be affected. Winter burn can affect all evergreens but yew, arborvitae, and hemlocks are particularly susceptible. Minimize winter burn by watering evergreens until the ground freezes in late autumn or early winter.

Construct a barrier around plants susceptible to winter burn to protect them from winter sun and wind. A second way that winter burn occurs is similar to sunscald damage on tree trunks. Cellular activity in evergreen foliage can be stimulated by sunny winter days that increase tissue temperature in evergreen foliage. When shading or sunset occurs, foliage temperature drops, resulting in foliage injury or mortality. Whether it is caused by transpiration and water loss or by sun's activation of foliage tissue, winter burn is an indication that evergreens were not sited properly in a landscape. A short term and aesthetically unappealing solution to this problem is to construct a barrier of burlap or cut evergreen branches around plants to protect them from winter sun and wind (Photo 2).

Don't apply antitranspirant sprays to prevent winter burn. Most research shows that antitranspirant sprays do not protect evergreens from winter burn.

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Photo 3: Narrow branch angle. J. O'Brien, USDA Forest Service,

Apply several inches of mulch around your trees and shrubs to buffer soil temperatures. Mulch is especially important at preventing cold injury to roots during snowless winters. Snow is a great insulator and moderator of soil temperatures. In its absence, several inches of mulch will help to moderate soil temperature.

Protect your trees and shrubs from animal damage. Rodents, rabbits, and deer feed on twigs, bark, and foliage during winter. In severe cases, their feeding can girdle and kill stems or entire plants. Deer rubbing their antlers on trees can also cause damage. Protect tree trunks and shrubs from rodent and rabbit feeding damage by using tree guards or a hardware cloth wrap. Start your protection a few inches below the ground for mice and extend it 24 inches above the average snow line for rabbit protection. Or protect entire beds from rodents, rabbits and deer with wire fencing, repellent sprays, or by hanging repellant-drenched rags.

Prune to prevent snow and ice damage. Prune to eliminate multiple leaders and narrow branch angles (Photo 3) between branches or branches and trunks of trees. Removing these weak branch attachments makes trees less susceptible to snow and ice damage.

Beware of Bed Bug Internet Hoax

Jeffrey Hahn, Asst. Extension Entomologist

There is a story making the rounds on the internet these days. It goes like this:

Hi All: A bit of information that you might like to know about. We have friends here in our community and one of their sons is an entomologist (insect expert), and has been telling them that there is an epidemic of bed bugs now occurring in America. Recently I have heard on the news that several stores in NYC have had to close due to bed bug problems, as well as a complete mall in New Jersey.


Photo 1: Bed bug. Jeff Hahn.

He says that since much of our clothing, sheets, towels, etc. now comes from companies outside of America, (sad but true), even the most expensive stores sell foreign clothing from China, Indonesia, etc. The bed bugs are coming in on the clothing as these countries do not consider them a problem. He recommends that if you buy any new clothing, even underwear and socks, sheets, towels, etc. that you bring them into the house and put them in your clothes dryer for at least 20 minutes. The heat will kill them and their eggs. DO NOT PURCHASE CLOTHES AND HANG THEM IN THE CLOSET FIRST. It does not matter what the price range is of the clothing, or if the outfit comes from the most expensive store known in the U.S. They still get shipments from these countries and the bugs can come in a box of scarves or anything else for that matter That is the reason why so many stores, many of them clothing stores have had to shut down in NYC and other places. All you need is to bring one item into the house that has bugs or eggs and you will go to hell and back trying to get rid of them. He travels all over the country as an adviser to many of these stores, as prevention and after they have the problem.

It is true that we are experiencing a significant increase in bed bug problems that has reached epidemic proportions. It is also true that a few retail stores have had bed bug problems and have had to temporarily close. However the rest of the story is unnecessarily alarmist and untrue.

While some clothing stores have found bed bugs, it is not because they were brought into the store on new clothes but rather they hitchhiked into stores on individuals that entered them. Fortunately, the incidence of bed bugs in clothing stores has been rare and owners have taken steps to prevent and better deal with bed bug problems. Because bed bugs would have a hard time finding a person resting for a period of time in clothing store, it is difficult for them to establish a reproducing colony which greatly reduces the risk of someone accidentally bringing bed bugs homes with them.

The idea that you need to worry about clothes you buy, especially those made in Asia, is an unfounded and false statement. The chances of bed bugs inadvertently hitching a ride in new clothes is extremely remote and there are not any known cases of this actually happening. If this was true, we would be routinely seeing bed bugs associated with clothing stores, instead of rarely.

This letter looks like it was meant to alarm and frighten people. Ignore it and continue to buy new clothes as you normally would. We have enough in things in our lives that gives us stress without unnecessarily adding to the list.

Prevent Snow Mold on Lawns Now

Michelle Grabowski, UMN Extension Educator

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Photo 1: Snow mold damage on a lawn in spring 2010Photo by T.Burnes.

In the spring of 2010 snow melted away from yards and landscapes to reveal round dinner plate sized patches of tan or gray matted turf. Two fungi, known as snow molds, were responsible for the damage. Many gardeners were dismayed to learn that little could be done in the spring to cure snow mold. Rather they had to wait for the weather to change and the grass to recover. This is because the time to prevent snow mold is not in the spring. The time is now.

Snow mold is caused by two different fungi, Microdochium nivale and Typhula sp. Both of these fungi thrive at temperatures just above or below freezing with high levels of moisture. Although snow cover is not a requirement for the growth for snow mold, snow cover provides ideal conditions for the fungi. Of course, gardeners cannot control how much snow Minnesota will receive this winter or how long that snow will stay. Gardeners can prepare their lawns for winter in a way that provides the best chance of a healthy spring.

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Photo 2: Fluffy white mycelia of snow mold can often be seen in moist conditions Photo by T.Burnes.

Several factors can increase the chances of snow mold the following spring. Long turf that is bent over by snow creates a canopy that traps humidity at the base of the turf plant. Piles of leaves or other debris on the lawn have a similar effect. Snow mold thrives in these humid microclimates. Fertilizing lawns in late September or early October can cause the grass to produce a flush of young succulent growth. This new succulent turf often does not have time to harden off before winter comes and is an easy meal for the snow mold fungi.

Several simple steps can be followed to prepare turf for the winter and reduce the risk of snow mold the following spring.

1. Rake up leaves and any other debris on the lawn.
2. Continue mowing until the grass goes dormant. A height of 2 inches will help the turf remain upright and facilitate air movement and drying of the turf.
3. Do not fertilize lawns until next year. A late season application of fertilizer can be done around Labor Day, but there is little benefit of fertilizing beyond that date.

Rust Diseases of Lawn Grasses Very Common this Fall

Bob Mugaas, UMN Extension Educator

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Photo 1: Areas of rust infection on Kentucky bluegrass lawn. Bob Mugaas.

Rust diseases of our lawn grasses have been on the increase throughout much of this fall period but became especially evident during the drier conditions of October. Rust infestations usually show up as areas of yellow to orange-yellow grass blades, see Picture 1.

Upon closer examination of the grass blade, one will usually see orange colored, tiny tuft-like pustules breaking through the grass leaf surface, see Picture 2. It is these pustules that produce massive numbers of individual spores. These are the same spores that can become air-borne and cover our shoes or lawn mowers in an orange 'powder' as we walk through rust infected areas of the lawn. They can also re-infect other grass plants that in turn can produce more of the same spore producing rust pustules thus carrying on the infection cycle.

What is a rust disease?

Rust diseases have very complex life cycles that include as many as five different stages during a single year. In addition, it is often necessary for various species of rust to spend a portion of their life cycle on one plant species and the other portion on an entirely different plant, often referred to as an alternate host. Such is the case with the specific rust disease known as crown rust (Puccinia coronata) of grass. This disease completes part of its lifecycle on its alternate host, common buckthorn (Rhamnus cathartica) or glossy buckthorn (Frangula alnus, formerly Rhamnus frangula), and the second portion of its lifecycle on some of our lawn grasses, especially perennial ryegrass and tall fescue. Other rust species including Puccinia graminis (Stem Rust) and Puccinia striiformis (Stripe Rust) can also affect Kentucky bluegrass, along with many other grass species.

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Photo 2: Spore producing rust pustles pushing through grass leaf surface. Bob Mugaas.

Rust on turfgrass can overwinter in plant debris but it will need to infect its alternate host before returning to the grass plant. It should also be noted that the disease causing spores can develop in warmer climates to our south and be blown up here during the summer and serve as a source of infection from summer into the middle of fall. This can be an important source of rust infection in this area. In a typical year and under favorable conditions, crown rust will usually start to show up toward the end of June while stem rust can be a bit later. Once begun, the rust infection cycle can continue throughout much of the growing season so long as favorable rust infection conditions persist.

Why rust and why now?

Slow growing lawn grasses are a prime target for rust disease attack. It is usually the combination of warm daytime temperatures, dry weather and heavy amounts of overnight dew production on the grass foliage that creates a favorable environment for rust spores to germinate and infect the foliage. When these common weather conditions are combined with low levels of available nitrogen, an element responsible for active, vigorous growth of our grasses, you have very favorable conditions for a rust outbreak. Shadier areas often experience greater incidence of rust. Note the lighter yellow to orange areas scattered around the lawn underneath the spruce trees in Picture 3.

Rust disease started showing up more frequently around the Twin Cities during late August to early September. However, it wasn't until the very dry conditions lasting nearly the entire month of October that significantly increased the occurrence of rust in our lawns and other turfgrass areas. Frequent enough rainfall combined with an occasional supplemental watering kept our lawn grasses actively growing and utilizing available nitrogen throughout much of the summer period.

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Photo 3: Rust infection on a partially shaded lawn area. Bob Mugaas.

Nitrogen can also be lost when it is carried with water down through the soil and beyond the reach of grass roots, a process known as leaching. Thus, due to relatively continuous grass growth during the summer and nitrogen losses due to leaching, it is quite likely that the amount of available soil nitrogen was in short supply by late summer, a time of year when our lawn grasses naturally resume active shoot and root growth. That condition along with the prevailing weather conditions during late September and much of October has contributed to a much higher than usual amount of rust disease on our lawns and other turfgrass areas.

So, what should I do now?

With the rains of the last few days of October, we have improved our previously dry soil conditions. That will be a big help in improving the growing conditions for lawn grasses. While it's late to be putting down nitrogen for this year, it would be a good idea to plan on applying some next spring as our lawns are beginning to show active growth. For the most part, we try to manage rust diseases by changes in our cultural practices. There are fungicides that can be applied in severe cases. However, at this late date in the season, both the rust fungi and the turfgrasses are preparing for winter survival and dormancy. Thus, fungicide applications at this time of year will be of no benefit. Use of protective fungicides can be reevaluated next year should serious rust problems begin to develop.

Where disease levels were quite high and there was some thinning of the lawn, one should be prepared to do some reseeding of those areas as needed. Some overseeding could be done yet this fall in a process known as dormant seeding. Normally this would be done once the ground is cold enough to prohibit germination with the seed remaining in the ground until next spring when it will sprout and grow. One could also wait until early next spring to do some seeding.

For some additional information on rust diseases of lawns, check out the following link to our Gardening Information page, What's Wrong with My Plant?

The author would like to gratefully acknowledge the input and review of Dr. Eric Watkins, Assistant Professor-Turfgrass Science, University of Minnesota Department of Horticultural Science and Michelle Grabowski, Extension Educator - Horticulture & Plant Pathology, University of Minnesota Extension, in the preparation of this article.

Calendar and Contributors: November 1, 2010

Garden Calendar

Check out more fall tips to reduce snow mold next spring from UMN Extension Educator Bob Mugaas, as featured with Bobby and Belinda on Kare11.

Be a responsible gardener and remove any buckthorn shrubs still growing on your property. They're easy to spot late in autumn when most other shrubs have lost their leaves. Buckthorn has green leaves and small clusters of black berries, with sharp barbs sparsley placed. Unfortunately, they're difficult to dig out. Larger plants will require brush killer next spring or summer. Do you have buckthorn in your yard? Learn more about buckthorn from the Minnesota DNR.

Buckthorn (R. Frangula) and all cultivars are considered to be restricted noxious weeds, according to the DNR. Check this list of Minnesota and Federal Prohibited and Noxious Plants by Scientific Name if you are ever uncertain about something in your yard.


The Yard and Garden News will now feature brief profiles of the contributors! We've asked UMN Extension Educator, Kathy Zuzek "What do you like most about your job?" and "What are you passionate about outside of work?"

Kathy Zuzek, UMN Extension Educator, Horticulture

The best parts of my job are being able to teach horticulture to invested students and working with other extension educators who enjoy helping others to learn as much as I do. During my 20 years as a research scientist I often commented on how much I enjoyed presenting to Master Gardeners, so becoming an Extension Educator and part of the Master Gardener education team was and continues to be a thrill.

I am passionate about plant hybridizing and developing attractive & adapted landscape cultivars for northern climates, parenthood, Minnesota's Arrowhead region, camping, hiking, kayaking, and my dogs (That's Max in the photo. Kirby, my golden retriever, missed that camping trip.)


Yard and Garden News Editor: Karl Foord
Technical Editor: Bridget Barton

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