University of Minnesota Extension
www.extension.umn.edu
612-624-1222
Menu Menu

Extension > Yard and Garden News > July 2009

Wednesday, July 15, 2009

Quick Update on Colorado Potato Beetles

Jeffrey Hahn, Asst. Extension Entomologist
art5-1_600.jpg

Do you have a problem with Colorado potato beetles in your garden? If you grow potatoes, there is a good chance you see them at one time or another on your plants. Don’t forget that in addition to potatoes, they can also attack eggplants, tomatoes and peppers. This insect can be challenging to manage but here are a few tactics you can use to deal with this pest.



Monitor susceptible plants regularly so you know if Colorado potato beetles are present in your garden. If you have a history of these insects in your garden, the odds are good you will see them again. Because you can have overlapping generations, you can find all life stages in your garden at any given time. Once they are active in spring, you will generally have Colorado potato beetles in your garden all summer.



If you have a smaller garden, and the time, handpicking is a great nonchemical control method. To be sure they are killed, just toss adults and larvae into a bucket of soapy water. For the really small, young larvae, just put on your gloves and squish them. And don’t forget the eggs. Look for them on the underside of the leaves. They are easy to recognize as they are orange and in clusters.



If physical removal is not practical, you may wish to use an insecticide. There are two low impact products available. Spinosad is produced by the fermentation of a soil-dwelling bacterium, Saccharopolysora spinosa. It is quick acting, attacking the nervous system of insects. It is most effective against caterpillars, flies (mostly leafminers), and thrips, as well as leaf beetles, grasshoppers and other insects that consume a lot of foliage.



art5-2_600.jpgNeem is derived from the neem tree, a plant found in arid tropical and subtropical areas. Neem can deter insect pests in one of several ways. They can inhibit their feeding, repel them, or disrupt their life cycle preventing them from successfully molting. Neem is generally effective against a wide array of insects, including beetles.



You might be wondering about Bacillus thuringiensis var. tenebrionis, a commonly used home garden product for leaf beetles, like Colorado potato beetles. This bacterial insecticide, which acts as a stomach poison, is quite effective against young larvae. However, this product is no longer registered in Minnesota. It was
previously available from Bonide in a product called Colorado Potato Beetle Beater. If you look at Bonide’s products, you will still find a product with that name, but it now contains spinosad.



There are a wide variety of residual insecticides, such as permethrin and carbaryl that are labeled to treat Colorado potato beetles. However, there is a good chance that the Colorado potato beetles in your garden are resistant to these insecticides already. This will be particularly true if you are any where near a commercial potato field. Instead try a newer insecticide, like esfenvalerate. The beetles in your garden are more likely to be susceptible to it.



What are Those Leaf Spots on my Tomatoes? - Speck, Spot or Something Else

Michelle Grabowski, University of Minnesota Extension Educator

art4-1_600.jpgSeveral kinds of blight are common on tomatoes grown in Minnesota. Almost every gardener has struggled with the fungal diseases Septoria leaf spot or early blight on their tomato plants at one time or another. This year bacteria are the primary pathogens being isolated from tomato leaf spots.


There are two bacteria that result in leaf spots on tomato; bacterial speck caused by Psuedomonas syringae pv. tomato and bacterial spot caused by Xanthomonas campestris pv. vesicatoria. Bacterial speck and spot can cause spots to form on the leaves, stems and fruit of tomato plants. The leaf spots caused by bacterial speck and spot look identical but the two pathogens can be distinguished by differing types of fruit spots that form later in the season.


Leaf spots are dark brown to black, small (about the size of a pencil tip) and have a yellow halo around them. Often the center of these leaf spots dry up and drop out leaving tiny holes throughout the leaf. If a leaf is infected with many leaf spots, the leaf may turn partially or completely yellow, and may even fall off. In past years, only minor infections from bacterial spec and spot have been observed in Minnesota. This year’s weather conditions seem to favor the pathogens, resulting in much more severe infections than previously seen.


art4-2_600.jpgSome varieties of tomato seem to be more sensitive to the bacterial pathogen than others. A few varieties, like Brandywine tomatoes, have been observed with larger leaf spots (up to 3/8th of an inch across). Infections with larger leaf spots could easily be confused with one of the common fungal leaf blight diseases. If gardener’s are unsure which pathogen they are dealing with, they should use the UMN Extension Online Diagnostic Tool What’s wrong with my plant? before making any management decisions.


On the tomato fruit, bacterial speck infections are small (the size of a pencil tip) raised black spots. These spots start on green fruit and may develop a green halo as the fruit turns red. In contrast, bacterial spot fruit infections are larger (the size of the eraser end of the pencil) dark brown to black, raised and often corky appearing. Bacterial spot infections may be surrounded by a white halo. In both cases, the infection on the tomato fruits remains fairly superficial and does not result in fruit rot.


Both bacterial speck and spot can come into the garden on infected seed or transplants. The bacteria are then easily transferred from plant to plant through splashing water, strong winds or on a gardener’s hands and tools. The bacteria survive Minnesota’s harsh winters in plant debris.


art4-3_600.jpgLuckily in most cases infection with bacterial speck and spot do not result in significant yield loss. Although the fruit with raised corky bacterial spots would not be considered marketable at the grocery store, smart gardeners know the fruit can still be enjoyed once the superficial spots have been cut away. Infected tomatoes should not be used for canning, however, because the disease may have changed the pH of the fruit.


To reduce the spread of the disease, gardeners should avoid working in tomato plants when the leaves are wet. Under moist conditions the bacteria reproduce and easily stick to a gardener’s hands and tools. Waiting until plants are dry for chores like staking, pruning and weeding will reduce the spread of the bacteria. In addition, providing good air movement around the plants by staking or caging tomatoes, pulling weeds, and spacing plants far apart will allow leaves to dry quickly. Allow 2 years to pass before planting tomatoes or peppers in the same location. Do not save seed from infected plants.



New Lily Classes Grow in Availability and Popularity

David C. Zlesak, University of Minnesota Extension Educator

Martagon, Asiatic, Oriental, trumpet, and tiger lilies (blooming approximately in this order from late spring through summer) are groups of amazing lilies that have beautifully graced our Minnesota gardens for decades. The martagon lilies have beautiful whorled foliage, flower early with wonderful clusters of typically downward facing flowers with recurved petals, and are even relatively shade tolerant. The Asiatic lilies are probably the easiest for us to grow here in Minnesota. In amenable sites they typically multiply well and provide a glorious show of blooms in probably the widest color range possible of all the different commercial lily classes. The Oriental and trumpet lilies have large, intoxicatingly fragrant flowers. The fragrance is especially powerful in the evening and throughout the night. I love coming home at night and being taken back by the rich, wafting fragrance of my Lilium regale lilies (a white trumpet lily) and ‘Casa Blanca’ Oriental lilies as I walk to the front door. Tiger lilies have magnificently speckled orange or yellow blooms typically with recurved petals similar to the martagon lilies.art3-1_600.jpg



art3-2_600.jpg We can routinely find cultivars of these traditional lily groups in our favorite catalogs and garden centers. However, in recent years there has been amazing advancements in very wide crosses between lily classes that previously were not able to produce successful offspring. Crosses between different classes have led to the development of new lily classes with many of the positive features of their parents. Special pollination techniques and techniques using tissue culture to “rescue” embryos have made it possible to recover hybrids from these wide crosses. These wide crosses are often called intersectional crosses because they are crosses made between different sections of the genus.




Botanically under the level of genus (Lilium is the genus of true lilies) there is the taxonomic level of section. Lily species that are within the same section are more similar genetically than lily species in different sections and tend to cross more easily among themselves (typically without the aid of tissue culture). For instance, crosses of multiple lily species in the section Sinomartagon led to the modern Asiatic lily cultivars we enjoy. Without tissue culture, sometimes intersectional hybrid embryos form, but the nutritive tissue (endosperm) around the embryo fails within a couple to few weeks after pollination and then it dies. If the embryo can be removed from the mother plant before it dies and placed in tissue culture where it can receive the nutrition it needs and continue growing. There are several modifications that can be made to the process in order to find ways that will work to recover different wide crosses.



These are some of the most popular intersectional lily classes on the market.




LA Hybrids


art3-3_600.jpg

LA refers to Longiflorum and Asiatic. These lilies are crosses between Easter lily (Lilium longiflorum) and Asiatic hybrids. They first came on the market in the early 1990’s. They look a lot like Asiatic lilies (flowers tend to be flat like Asiatics), but tend to have larger flowers with thicker petals than the Easter lily parent. Early LA hybrids tended to have colors within the pastel shades. Breeders have been able to backcross
early LA hybrids to Asiatic lilies to intensify color and strengthen hardiness and other traits. Interestingly, breeders have not reported successful backcross hybrids to Easter lily parents. Modern LA hybrids tend to be as durable in Minnesota as Asiatic lilies. They are used widely in the cut flower industry and tend to be relatively easy to force in pots like Easter lilies.



Orienpet Hybrids


art3-4_600.jpg

Orienpets are crosses between Oriental and trumpet lilies. They tend to have huge, wonderfully fragrant flowers in a very wide array of colors and color combinations. The flowers generally tend to be more open faced like the Oriental parent. In Minnesota Orienpets tend to be more adaptable and durable than Oriental lilies. Plants typically are quite large. Many common Orienpet hybrids routinely grow to about 6’ tall and benefit from staking. The North American Lily Society has a yearly popularity poll. Those that win over multiple years are eligible to eventually be elevated into the lily Hall of Fame. Two very popular Hall of Fame lilies are of the Orienpet class and are ‘Silk Road’ and ‘Scheherazade’.
‘Silk Road’ is a lovely red / white bicolor and ‘Scheherazade’ is beautiful red / yellow bicolor.



LO Hybrids


art3-5_600.jpg

LO hybrids are crosses of Easter lily and Oriental lilies. They have just come into the marketplace the past few years. The most common cultivar gardeners are likely to find is ‘Triumphator’. In many ways it looks like an Easter lily with its beautiful, elongated trumpet, but the throat of the bloom is a gorgeous, rich red. It will be exciting to see more LO cultivars come on the market in the near future. Early reports are favorable for
‘Triumphator’ being able to overwinter in Minnesota. More time is needed to be confident how well cutivars of this new class will routinely perform in Minnesota.



Progress is being made on additional intersectional classes. For instance, there are beautiful hybrids in existence between martagon and Asiatic lilies. Hopefully soon they will become widely available. Recent intersectional lily hybrids offer even more great lily options for the Minnesota gardener.




The North American Lily Society (NALS) is a great resource to learn more about lilies. There are also local chapters. In addition, NALS has a nice seed exchange they host each year where members can obtain seeds of amazing lily species and also seeds of crosses and open pollination of lilies in almost every major class.



Clematis Growth Types and Pruning

Karl Foord, University of Minnesota Extension Educator


art1-1_600.jpgClematis is a genus that is best known for its vining members that produce large, colorful, showy flowers. This is at best only half of the truth. In fact many of the cultivars do produce spectacular flowers with colors from almost all 360 degrees in the gardener’s color wheel. In addition there are varieties with smaller nodding flowers that add a certain delicacy to the garden as well as some herbaceous types that are more shrub-like and die back to the ground each year. Clematis require a certain effort to make them thrive but it is well worth the effort.


The dizzying array of cultivars can be intimidating, but this can be simplified by categorizing plant types by when they set their flower buds. This will then determine when they will flower and how they should be pruned. As such, the categories are often labeled as pruning groups.




Group A*


art1-2_600.jpg

In this group flower buds are initiated on this year’s vine in July and then produce flowers in the late spring of the following year. If you prune off old wood you also prune off flower buds. So if you have a clematis vine and do not know the variety, observe its time of flowering. Those that flower before early summer are likely in this group. Pruning of this type should only serve to maintain the framework. Do so only after flowering and before July. Common species in this group include Clematis alpina and C. macropetala and are characterized by smaller 1” to 3” nodding flowers. Clematis alpina ‘Pamela Jackman’ and C. macropetala ‘Markhams Pink’ are cultivars of these groups that flower in May and thereafter produce attractive seed heads. Simple Rule: “If a clematis flowers before early summer, do not prune it.”(1)



Groups B1 & B2


In this group flower buds are produced on both old and new wood. The group can be divided into varieties that have two flower flushes (B1) and continuous flowering (B2). (2)art1-3_600.jpg



The B1 group flowers in early summer (May-June) from buds initiated the previous summer and in late summer (September) from buds initiated on the current year’s growth. The late summer flush is typically smaller than the early summer flush. Cultivars showing this pattern of flowering are ‘Haku Ookan’, ‘Miss Bateman’, ‘Lincoln Star’, and ‘Nelly Moser’. Interestingly, the cultivars ‘Belle of Woking’ and ‘Daniel Deronda’ produce double and semi-double flowers, respectively from old wood and single flowers from new wood.



art1-4_600.jpgRemove dead and weak stems in late spring prune after first flush of growth. Simple Rule: “Do not indulge in large-scale pruning of old wood made during the previous season(s) or there will be a loss of early flowers.”(2)


The B2 group shows a continuous flowering pattern lasting from June to September. Flower buds were initiated the previous year (old wood) and in the current year (new wood) in the same manner as the B1 group. However, this group does not demonstrate a rest period between two growth flushes. Cultivars showing this flowering pattern are ‘The President’ and ‘General Sikorski’ (photo).



Group C


art1-5_600.jpg

Group C plants only initiate flower buds on the current year’s growth. This pushes the flowering time to later in the season- July through September. The goal in pruning this group is to eliminate all of last year’s growth and leave the lowest pair of live buds on the plant to begin the current season’s growth. This encourages plants to produce strong new shoots from the base and flower well. Typical of this flowering pattern are the Tangutica, Texensis and Viticella groups and cultivars ‘Madame Julia Correvon’ (photos). Clematis integrifolia is a group C plant with a bush habit that only reaches two to three feet in height (photo).


art1-6_600.jpgI recommend that you consider clematis for your garden or if you have some already, consider adding more as part of you next gardening adventure. Always provide a climbing surface for the climbing clematis forms and secure stems to the surface. If this is not done winds can buffet and break the vines leading to a very unsatisfactory outcome.



*The A, B1 & B2, and C groups are often named 1, 2, and 3, respectively by some authors.




References



  1. Mary Toomey & Everett Leeds, An Illustrated Encyclopedia of Clematis, Timber Press, Portland, Oregon, 2001.

  2. Fred Wein et. al., The Concise Guide to Clematis in North America, Clearview Horticultural Products Inc., Home of ClematisTM

University of Minnesota Edible Landscape - A Demonstration Garden Incorporating Fruit and Vegetables into the Home Landscape

David C. Zlesak, University of Minnesota Extension Educator

art2-1_600.jpgEarlier this year in the May 15th Yard & Garden News, we featured Emily Tepe’s informative article on Woolch™ in the Mid-May Yard and Garden News as a new mulch for both commercial and home garden use. Emily planted a fantastic demonstration garden where Woolch™ would be featured. She invited us to come and see this garden on the St. Paul campus in front of the Plant Growth Facilities near the ‘Seed of Knowledge’ sculpture (across the street from the Display and Trial Garden). This garden is looking great and has much more to see in addition to strawberries and other plants growing with Woolch™. This garden integrates fruits, vegetables, and flowers into a very ornamental and functional landscape. Please come and visit the garden this summer. If you are not able to make it out or would like to just learn more about this great garden, Emily has created a blog about the garden at http://umediblelandscape.blogspot.com.




Wednesday, July 1, 2009

What's Up With That?!

wuwt_300.jpg

David C. Zlesak


Why do dandelions all look so similar? Other plants that reseed tend to result in individuals that have noticeable differences from each other. These differences among seedlings may be dramatic or subtle and can involve traits such as flower color, petal number, or plant habit. The answer is that dandelions primarily reproduce by apomixis. Apomixis is commonly defined as asexual reproduction through seeds. The embryos are genetically the same as the mother plant and are not the result of the union of two sex cells. Most plant and animal species rely on sexual reproduction to enhance genetic variability among individuals in populations. Variability can improve the chance that at least some individuals will have a competitive advantage when disease or other challenges come. Those individuals will hopefully survive and be able to reproduce in order to perpetuate the species. Dandelions, some turf grass species, and many citrus have a different strategy that uses apomixis. The best, well-adapted individuals clone or copy themselves through seed. A relatively small proportion of embryos are the product of sexual reproduction to support variability, while most are genetic copies of the well-adapted mother plant.


Photo 1: Bob Mugaas



Rose Acacia - A Shrub with Showy Pink Flowers

art1-1_600.jpg

David C. Zlesak, University of Minnesota Extension Educator


Rose acacia (Robinia hispida) is in full flower across Minnesota. It is a plant many people are unfamiliar with and are asking what it is. The abundant pendulous clusters of rosey pink, pea-shaped flowers makes it especially showy this time of year. Although it is native to the Southeastern United States and is often listed as hardy to zones 5 or 6, forms of it are perfectly adapted across Minnesota and do not suffer dieback. Although not readily for sale in the garden centers, once planted (typically shared among friends) it tends to persist. The amount of it therefore continues to increase across Minnesota landscapes.




Photo 1: Rose acacia flowers are showy and produced over an extended period. David Zlesak


art1-2_600.jpg

It is an easy to grow plant because of its tolerance to poor soil and drought. Often it is seen growing on old farmsteads or along the roadside. The plant habit is somewhat open and airy because of coarse stems and its compound leaves. It typically reaches 8-10 feet in height. It suckers and spreads over time into thickets, which makes appropriate placement very important. Young shoots can easily be pulled if one is persistent, but if cultivated it is best to place it in a confined area or area where it can be permitted to spread. Stands of it in Minnesota typically do not set viable seed. Because of its vigor, it is recommended not to let it escape cultivation.


Photo 2: Rose acacia can grow into an open, spreading thicket. David Zlesak


Other common names for rose acacia include hairy or bristly locust. This is because the stems are covered with soft bristles. It can set multiple clusters of flowers on each stem resulting in an extended bloom time.


art1-3_600.jpg

Photo 3: This locust growing in Excelsior, MN is likely a hybrid of black locust and rose acacia. David Zlesak


Rose acacia is a species of locust and is closely related to black locust (Robinia psuedoacacia). Black locust is a full-sized tree that has clusters of white, pea shaped flowers. Crosses have been made between the two species and we can periodically find the hybrids for sale in garden centers such as 'Casque Rouge' and ‘Purple Crown’. The hybrids typically grow into smaller trees than black locust and have flowers that are soft to medium pink. The hybrids have typically been selected to have limited suckering. Both locust species and the hybrids can sucker, especially when the roots have been disturbed. Because of this they tend to be used sparingly in typical landscapes.


Hennepin County Master Gardener Garden Tour July 11th from 9am-4pm

art2-1_600.jpg

You are invited! Come and join us for our 2nd Annual Hennepin County Master Gardeners Learning Garden Tour. We have 10 very unique gardens designed and maintained by Master Gardeners for you to enjoy. The Master Gardener homeowner and other Master Gardeners will be on site to respond to your questions. For a preview of some of some of the gardens and event please view this video.


Each garden has a different theme and demonstration. Themes include a fairytale garden, a low maintenance garden, urban and woodland retreat gardens, a farmhouse in the city, container gardening, a sanctuary garden, and a shade garden with a labyrinth. There will be practical, informative demonstrations at each site. Master Gardeners will conduct interactive demonstrations at 10, 12, and 2 p.m. on a wide range of topics. You can learn how to create small space, container, and vertical gardens, build low maintenance water gardens in a weekend, create garden rooms and rain gardens, using color to create moods, and how to grow vegetables.




Photo 1: David C. Zlesak


Our very popular boutique will feature garden related crafts, concrete leaves and stepping stones, gardening books, and other items for sale.


All ten gardens are clustered in the Edina-South Minneapolis-and Bryn Mawr area to minimize your driving time. The intent of the tour is to provide you with an interactive and informative experience. Bring your questions! Bring your camera!


Proceeds benefit Hennepin County Master Gardener community programs.


Tour details:

Date: July 11, 2009

Times: 9am to 4pm, rain or shine.

Price: $15 per person when purchased prior to the event, $20 the day of the event. Tickets can be ordered onlineby clicking the "Buy Now" button on this website. Make sure you click the "Return to the U ofMN Hennepin County MG" button at the end of your order toreceive a list of garden locations and print your receipt.Or, you can stop by the HCMG office located at 479 Prairie Center Drive, Eden Prairie. Call 612.596.2130 for more information.


The price of admission includes:



  • Entry into all ten gardens

  • A brochure with site descriptions, locations, and driving instructions

  • Demonstrations

  • Free flower and vegetable seeds

  • Free handouts on selected yard and garden topics



Lawn Mushrooms

art3-1_600.jpg

Bob Mugaas, University of Minnesota Extension Educator


With some areas of the state receiving moderate to heavy amounts of rainfall over the past couple of weeks, mushrooms are beginning to randomly appear in lawnsTheir appearance often causes people to be concerned about the health of their lawn and whether or not a serious disease might be getting started.


It’s important to remember that mushrooms are the ‘fruiting bodies’ of fungi living in the soil and thatch. They are responsible for the production of microscopic spores that in turn help propagate the fungus. The vast majority of those fungi are not associated with any lawn disease causing organisms. It’s quite common for them to appear during periods of moist conditions resulting from either natural rainfall or excessive irrigation. Again, they are not necessarily indicative of any particular lawn problem. The fungi are living on decaying organic matter in the soil and/or thatch layers. This breakdown of organic matter results in at least some of the nutrients contained in that organic matter being released back to the soil. At that point the nutrients are available for continued plant growth or used by other microorganisms. If you find the mushrooms offensive, simply knock them over with a rake and remove them from the area.




Photo 1: Newly emerging lawn mushrooms. Bob Mugaas


art3-2_600.jpg

The one exception to the above situation is a lawn problem known as fairy ring. Symptoms in the lawns appear as dark green arcs and/or circles; often darker than the surrounding grass on either side of the ring or arc. There are a number of different fungal organisms associated with the production of these arcs or circles. If you suspect this problem is in your lawn please view this link on fairy rings which is part of the diagnostics feature on the University of Minnesota Extension Gardening Information website.


Photo 2: Typical lawn ‘fairy ring’ symptom. Bob Mugaas


Choose Weed Control Products Carefully

art3-3_600.jpg

Bob Mugaas, University of Minnesota Extension Educator


When trying to select the ‘right’ weed control product, consumers are often confronted with a bewildering array of possibilities at retail gardening outlets. This prompts the honest question of ‘Which one of these products should I choose?’ Likewise, this question can have a variety of responses depending on what weeds are being targeted. This could easily be the topic of several articles.


However, there is one word of caution that is worth noting. Nonselective weed killers, that is, those that will kill all green vegetation, should not be used to treat weeds in lawns and expect the lawn not to be damaged. The result will end up like pictured where all the plants that contacted the herbicide, including the lawn grasses are killed leaving small to large patches of brown dead grass. These will now need to be reseeded or resodded since none of the grasses in these areas will come back. The two most common ingredients in these types of herbicides are glyphosate (e.g., Round-up, Kleen-up, many others) and glufosinate – ammonium (e.g., Finale). These should not be used to treat weeds in lawn areas unless the desire is to kill both the existing grass and weeds such as might be done before installing a new lawn.




Photo 1: Lawn damage resulting from a non-selective herbicide application. Bob Mugaas


For more information on homeowner available herbicides and how to go about choosing an appropriate weed control product, see the article on weed control in the May 15, 2008 Yard and Garden Newsletter.


July often signals the time to be extra careful when using weed control products as lawn grasses can be injured and/or weeds not controlled very well. The reason, high temperatures accompanied by often dry conditions. This puts our lawn grasses under stress and often slows the growth of both weeds and grasses. Product label directions will usually give specific temperature ranges for when their product should and should not be used. It is important to follow those directions exactly not only because it will minimize the chances for injury to desirable lawn grasses but it’s a violation of federal law to use the product in ways that are inconsistent with its label. Also, the return of cooler temperatures and usually more rainfall later in the summer is usually a much better time to control perennial broadleaf weeds. Unless absolutely necessary, postpone control of these weeds until later in the season.


Thousands Visit Morris Bedding Plant Trials

art4-1_600.jpg

Steve Poppe, University of Minnesota Scientist, West Central Research and Outreach Center


In the past, no other segment of the floriculture production industry has enjoyed public interest and use of its product more than bedding plants (annual flowering plants). Bedding plants are an indispensable item for landscape use, presenting an array of flowers and foliage that add color and texture to the landscapes of homes, apartment complexes, shopping malls, public buildings, city streets and parks.


The University of Minnesota supports this growing industry through annual flower trials conducted at Morris, St. Paul and Grand Rapids. In 2008, we evaluated annual flowers from eighteen major plant companies. Our gardens are open to the public and industry for selfguided tours throughout the growing season, providing a unique opportunity to compare performance of bedding plant cultivars under regional conditions. The public's response to the 2008display gardens at all locations was very positive. Several thousand people visited these sites during the summer. Numerous educational programs and garden tours were provided at all sites, highlighting the outstanding annuals in our trials.




Photo 1: Thousands of well-labeled annuals and perennials make the gardens a great educational resource. Dave Hanson


The three annual flower test locations represent three very distinct climates. The St. Paul site has cool springs and hot summers and offers a good test of plants in a large metropolitan area. The Grand Rapids site has a short growing season and cool summer temperatures, and the Morris site has typically hot, dry summers with more wind than the other two sites.


Annual flower trials evaluate plant height, width, and uniformity; flower size; flower and plant quality characteristics; and disease resistance for a wide variety of annuals. Cultivars are grown from seed or are vegetatively propagated. They are planted and rated periodically for field performance. Home gardeners and commercial bedding plant producers can identify cultivars best suited for their locations from evaluations of over 400annual flowers.


art4-2_600.jpg

New and recent annuals and perennials are obtained from leading industry members to determine their performance in our climate. Dave Hanson


All three locations have been All America Selections Display Gardens, (AAS) since 1990, and grow the AAS winners from the past five years. The AAS Award recognizes a flower or vegetable variety proven to be superior to all others on the market. An AAS Display Garden provides the public an opportunity to view the new AAS winners in an attractive, well maintained setting. Additionally, Display Gardens provide educational AAS programs during "open house" or "field day" events during the peak season for garden flowers and vegetables.


A goal of the West Central Research and Outreach Center (WCROC) in Morris is to establish a regionally recognized public research garden. The WCROC offers an aesthetically-pleasing garden where interested gardeners can learn and share ideas, and students can work and learn about plants and the environment. Recent and on-going projects support our goal of providing research and evaluation of horticulture plants in an exciting and enjoyable setting. Examples of such projects and events include:


Horticulture Night – Horticulture Night has become the WCROC's premier regional event, attracting over 1,400 visitors annually. It is held the last Thursday in July from 5:00 to 9:00 p.m. Visitors participate in walking tours of horticulture research and display gardens and enjoy special landscape and garden demonstrations. In addition to tours and displays, young and old enjoy dozens of fun, hands-on activities. Horticulture trade show vendors keep visitors updated on the latest plant materials, garden supplies, landscaping and lawn care products, equipment and available services.


art4-3_600.jpg

Photo 3: Shrubs such as roses are also featured in the garden. David Zlesak


Pomme de Terre Overlook – This new fifteen acre overlook connects the WCROC's agriculture, horticulture and renewable energy research with the people and natural resources of west central Minnesota. The trail system connects the existing children's garden, research and display garden, woody arboretum, and restored native prairie area with the Morris city bike / walking trail system and its largest city park. The overlook enhances the WCROC's status as a regional and statewide natural resource educational destination.


Low Input Sustainable Turfgrass Trial - The University of Minnesota Turfgrass Science Program is developing low-input turf for the Upper Midwest. We are evaluating the potential of native and non-native turfgrass species for use as turf in low and medium maintenance situations. There is a great need for more information about turfgrass mixtures in low-input management situations (reduced mowing, no irrigation, less fertilization, etc.).


We established a low-input turfgrass evaluation trial at Morris in the fall of 2007. The study examines the usefulness of 10 grass species with 3 replications of both monocultures and mixtures at various management levels. The trial is mowed monthly at a height of 3 inches during the growing season, clippings returned. No irrigation, fertilizer, or pesticides are applied. Data collection includes turfgrass quality, stand density, weed pressure, drought tolerance, vigor, diseases identified and evaporative transpiration recorded. Dr Eric Watkins from the University of Minnesota, Department of Horticultural Science, is coordinating this experiment and results will be shared after the 2009 growing season.


High Tunnel Raspberries - In 2008, we experienced our first growing season with an experimental trial of fall-bearing raspberries in our high tunnel plastic hoop house. This project is the first to experimentally assess high tunnel raspberry production in Minnesota.


art4-4_600.jpg

Photo 4: High tunnels are being studied for their use in season extension of primocane fruiting raspberries. David Zlesak


Minnesota growers of horticultural crops are constrained by the short growing season and cold winter temperatures. Techniques enabling growers to extend the season for marketing later into the fall would be a significant economic benefit. Researchers have estimated between 20 to 100% loss of fruit on primocane fruiting (fall-bearing) raspberries when freezes occur before September 15th in Minnesota. Unheated high tunnels, consisting of a metal frame covered by polyethylene, have allowed horticultural producers to extend the production season of certain crops.


The primary goal of our high tunnel raspberry production research team is to minimize the impact of farming practices on human health and the environment. Eliminating fungicide and herbicide use in raspberry production and minimizing insecticide use will result in cleaner water and safer food. In addition, we aim to:



  • Determine the length of season extension offered through the use of high tunnels in Minnesota

  • Determine the effect of high tunnels on plant-growth and fruit quality

  • Evaluate three fall-bearing cultivars (Autumn Britten, Caroline, Joan J) and two plant spacing's to determine optimal choices for high tunnel grown raspberries in Minnesota!


Horticulture Night- July 30, 2009 (5-9PM)

West Central Research and Outreach Gardens, State Hwy. 329, Morris, MN


Come for a fun-filled, educational evening for the whole family. There will be garden tours, demonstrations, food, vendors, and more. Please call 320-589-1711 if you have questions.


'Go Green with a Splash Party' Weekend at the University of Minnesota Landscape Arboretum Saturday and Sunday, July 11 & 12

art5-1_600.jpg

This special weekend features an information fair and water-wise demonstrations, art activities, music and a Heart of the Beast Puppet Theatre performance! Part of the 2009 Waterosity theme, this special weekend brings together additional resources and events surrounding the theme of water usage and water-wise practices. Here are just some of the special highlights:


The renowned In the Heart of the Beast Puppet and Mask Theatre will present Are You Thirsty?" (11 a.m. & 1 p.m. July 11 & 12).


Performances will be free with Arboretum admission.


Volunteers will be on hand to help showcase the various exhibits


The information fair will include several area industry and non-profit groups that are involved in water use and management.


While at the Arboretum, don’t miss all the great art displays dispersed throughout the grounds. The over a dozen special art displays celebrating Waterosity will be in place through early October. Artists far and wide submitted ideas this past year for consideration and a subset were selected for implementation. Here are just a couple highlights!




art5-2_600.jpg

‘Simple Lines’


Designer: Mike Helbing, artist, Chicago, IL


Derived from the natural elegance of an unfolding fiddlehead, veins of a leaf or trees in winter, this fountain describes the peacefulness of the Arboretum woods. It reflects an attitude of working with and accepting nature while bending it to our benefit and needs. This sculpture works as an aerator to provide oxygen to the water in the pond. Its form provides aesthetic joy, and, as a tree stripped bare of leave, it also has beauty when the water is off.




art5-3_600.jpg

‘Global Spydrology’


Designers: Sean Jergens, Landscape Architect, ASLA, RLA; Sandra Rolph, Landscape Designer, ASLA, LOOD AP; Jenny Salita, Landscape Designer / Urban Planner, ASLA, Minneapolis, MN


Discover the ‘water stories’ of people from 12 countries, from tiny Malta to the U.S.A. Each steel column grouping shows the average daily freshwater use by one citizen of that country in a single day. Agricultural irrigation dominates freshwater use, as highlighted by the spiral planting of wheat. Consider water as a vital, valuable, shared global resource.


Water-Wise Gardening

art6-1_600.jpg
Julie Weisenhorn and Kathy Zuzek, Director, University of Minnesota Master Gardener Volunteer Program & University of Minnesota Extension Educator

Watering your garden and lawn… it seems so straight forward. When the soil is dry or a plant wilts, water. If it doesn’t rain for two weeks, water. If you happen to have the hose on, sprinkle on a little water.

Not so. There are many factors – the type of soil and the amount of sun and wind in your yard, the types of plants that you grow, weather patterns, and your cultural practices – that play into a landscape’s water needs. The water-wise gardener considers and plans for these factors to produce beautiful landscapes while minimizing water use.


Photo 1: Understanding factors in ones yard that impact water availability will help one choose amenable plants, cultural techniques, and water management strategies. David Zlesak

Study your Yard

Let’s address the soil first. Knowing your soil type – sandy, loam, clay – is the most important factor when determining how much and how often to water. Having your soil tested at the University of Minnesota Soil Test Lab (www.soils.umn.edu) is a reliable, easy, and inexpensive way to find out what kinds of soil your yard contains. On one end of the soil spectrum are sandy soils with their large particles that allow water and nutrients to drain and leach away quickly, leaving you with a low-fertility soil that dries out quickly. On the other end are clay soils with their small particle sizes packed so closely together that there is little space between particles. As a result clay soils are prone to poor drainage, low air porosity, and compaction. It is not hard to figure out why sandy and clay soils are often called “problem” soils and that sandy soils will need more frequent watering than clay soils.

Adding organic matter- compost, peat moss, composted manure - will do wonders to improve the water-holding capacity of both sandy and clay soils. Compost-amended sandy soils will do a better job of holding on to water and nutrients. In clay soils, compost will improve the arrangement of all of the small particles, increasing the air space, so that oxygen is more available to plant roots and water drainage improves. With both soil types, adding compost improves the balance of water, oxygen, and nutrients in the soils, making it easier to grow healthy plants with lower input from you the gardener. For more information on soil amending and compost please visit Amending Soils for Perennial Beds.

art6-2_600.jpg
Photo 2: Adding compost or other sources of organic matter to soil will help improve its water holding capacity. David Zlesak

The light levels in your yard – full sun, partial shade, or full shade – and your yard’s exposure to wind affects the moisture level of soils and how often you have to water plants. Sunnier and windier sites will need more frequent watering that more protected and shadier sites.

Right Plant for the Right Place

As you design your gardens and browse through your favorite garden center, remember to pick plants that will grow well in the soil types and light levels of your yard. If you want to minimize watering or have sandy soils, choose plant varieties such as sedum and low bush honeysuckle that tolerate drier conditions and require less water. Plants like turtlehead and red-twigged dogwood that prefer moist soil areas would do poorly under dry conditions.

art6-3_600.jpg
Photo 3: Matching plants tolerant of the locations in which they are placed will go a long way in ensuring success. This hosta was planted in too much sun and did not receive adequate moisture. David Zlesak

Remember that some plants do well in full sun, others in partial or full shade. Attractive companion plantings chosen both for visual appeal and common water and light requirements will produce the healthiest and most beautiful landscapes while minimizing water requirements. For more guidelines about plant selection, visit the University’s website Sustainable Urban Landscape Information Series (SULIS) at www.sustland.umn.edu.

Water-wise Cultural Practices

It’s planting time. Spacing of plants plays a role in watering needs too. Placing plants too closely together will increase the competition between the plants for resources such as water and nutrients. Be sure to space plants based on their mature size, allowing them to grow to their full potential above and below ground to minimize plant stress.

Organic mulches – wood chips, shredded bark, pine needles, straw, grass clippings, shredded leaves - are great tools for the water-wise gardener. A three- to four-inch layer of mulch over a garden buffers soil temperatures and serves as a barrier that slows the rate of water evaporation from soil into the air. The net result is less fluctuation in soil moisture and more water available to plant roots, which improves root growth while reducing irrigation needs. In addition, as organic mulches break down, they add organic matter to soils, improving the water-holding capacity of soils.

art6-4_600.jpg
Photo 4: Organic mulches have many benefits to plants including helping to conserve moisture. David Zlesak

Mulches discourage weed growth in our gardens, eliminating the competition for water between our landscape plants and weeds.

Woody plants and turfgrass don’t coexist well. We have all struggled to keep sun-loving grass varieties alive under the canopy of a tree. But with their density and close proximity to soil surfaces, turfgrass roots enjoy a competitive advantage when they cover tree and shrub roots, and siphon off vast amounts of water. This is an even bigger problem during periods of drought, creating a double dose of stress for woody plants. Replacing turf around trees and shrubs with an organic mulch eliminates all of these problems and reduces irrigation needs – no more pouring water on grass struggling to grow in shade, no more grass roots stealing water from roots of woody plants, and less evaporation of water from mulched soils around trees and shrubs. For more information on mulching, visit Mulching and Watering.

How about watering our plants efficiently to conserve water? Efficient irrigation means applying water in the proper amount, proper location, and only when it is needed.

How do you know when you should water? As a rule of thumb, water infrequently but do water before plants wilt. When you do water, give plants a deep thorough soaking. Frequent, shallow watering causes plants to produce shallow root systems that cannot survive the heat and dry conditions of mid-summer months. Watering deeply and infrequently causes plant roots to grow deeply into the soil in search of water, resulting in deeply rooted, more drought-resistant plants. Remember that sandier soils, higher temperatures and wind velocities, periods of drought, and recently-planted gardens all require increased watering.

Watering in early morning when evaporation rates are low conserves water.

art6-5_600.jpg
Photo 5: If you use a sprinkler, watering early in the morning helps to conserve water. David Zlesak

Applying water at the root zone of plants either by hand or through drip irrigation is another water-wise practice. Drip irrigation is the slow application of water directly to the plant's root zone using emitters spaced along tubing lying on the ground. Water is absorbed slowly and more deeply into the soil and root zone, helping to maintain the right balance of water and air in the soil while promoting deeper root growth. No water is wasted on non-growth areas, evaporation is reduced, and runoff and wind-blown water is avoided, making drip irrigation a great water conservation practice. For more information on drip irrigation, visit Drip Irrigation for Home Gardens and Drip Irrigation Tutorial.

How efficient are automated sprinkler systems? The design of an automated sprinkler system determines its efficiency. But an efficient irrigation system can still waste water if it is programmed to run too often or too long. Initial programming and seasonal adjustments to the program of an automatic sprinkler system should be based on the type of plants you are growing and their water needs, soil type, seasonal temperatures and moisture levels, and exposure of your site to light and wind. Adjusting your sprinkler’s programming seasonally both conserves water and improves plant health by matching water applied to plants’ needs.

art6-6_600.jpg
Photo 6: Automated irrigation systems can help to efficiently deliver water if set up considering site, plants, and time of year. David Zlesak

Rain sensors incorporated into your automated irrigation system are another water-conserving tool. Automatic rain shut-offs turn controllers off when there is sufficient rainfall. Your controller’s manual override will do the same thing, but for people often away from home, rain sensors are a great alternative. For more information on efficient irrigation and home irrigation systems, please visit Operating and Maintaining a Home Irrigation System.

The Cutting Edge Lawn Care Exhibit

art7-1_600.jpg
Bob Mugaas, University of Minnesota Extension Educator

The Cutting Edge is an educational display that is part of the 2009 Minnesota Landscape Arboretum’s Waterosity Educational Exhibit. The display focuses on how more water conservative lawn grasses combined with some small changes in lawn care practices can reduce water needs and other inputs going into the lawn.

The exhibit features small plots of several lower maintenance lawn grasses that are starting to see greater use in more water conservative lawns. For more information on low maintenance grasses, please visit Cool Season Grass Selection. Additionally, a plot of tall fescue, an up and coming turfgrass species with good drought tolerance and some adaptability to shady conditions, is featured. Prairie junegrass, a native of Minnesota prairies, is also be on display as it would appear in a lawn situation. As it already has very good drought tolerance, this shorter growing native species is currently involved in a rigorous U of M plant breeding program to increase other desirable lawn grass characteristics. In addition to viewing separate species and varieties of lawn grasses, both a no-mow mix and an ecology lawn mix are on display to provide yet another alternative to a traditionally managed lawn. For more information on turfgrass research at the University of Minnesota please visit Turfgrass Science and click on the research tab.



Photo 1: The Cutting Edge display is located in front of the visitors’ center. Educational displays are within the log house and turf plots and other water wise displays surround it. David Zlesak

art7-2_600.jpg
Photo 2: Plots of traditional and lower maintenance turf species labeled with their relative water needs, foot traffic tolerance, and mowing frequency are featured in the Cutting Edge display. David Zlesak

Cultural practices play a very important role in determining water needs of lawn grasses. For example, the practice of raising mowing heights will encourage deeper rooting, thereby providing greater access to soil moisture reserves. Shorter mowing heights restrict rooting depth and make lawn grasses more dependent on us to meet all of their water needs. For additional information on mowing please visit Mowing Practices.

There will be special displays in the Cutting Edge regarding a variety of different watering practices and products. Information and displays on the use of mulches in landscape beds and gardens to help conserve soil moisture, reduce weeds and lower soil temperatures will be featured. Smart watering accessories like timers and automated control systems will be on display. Something as simple as a timer positioned between the garden hose and the outdoor faucet provides better control over how long watering will occur. In automated systems, soil moisture sensors can tell the system when the soil is wet enough and doesn’t need any more water and will also shut the system off when it’s raining.

art7-3_600.jpg
Photo 3: Creative educational displays help to make learning about water wise lawn care engaging and fun. David Zlesak

The Cutting Edge display provides many ideas that homeowners can adopt to conserve water in the managing of their lawns and other landscape areas. Folks are invited to come observe and interact with the various elements of the Cutting Edge.

In-depth information on watering lawns can be found at Sustainable Lawncare Information Series' Watering Practices.

Drought-Tolerant Plants

Kathy Zuzek, University of Minnesota Extension Educator

art8-1_600.jpg
Do you live in a geographic area with little rainfall? Do your sandy soils allow water to percolate away quickly? Are you looking for a drought-resistant landscape? Are attractive landscapes and water conservation both goals of yours? Below is a partial list of trees, shrubs, and herbaceous perennials that once established, grow well with little supplemental watering. Within most of the species listed, there are cultivar choices that will provide you with a wide variety of ornamental traits.



Photo 1: Japanese tree lilac. Kathy Zuzek

Deciduous Trees
Common NameScientific NameExposure*
Autumn Gold Ginkgo Ginkgo biloba ‘Autumn Gold’S
Black Walnut Juglans nigra S
Blue BeechCarpinus carolinianaS/Psh/Sh
Bur OakQuercus macrocarpa S
Cockspur hawthornCrataegus crus-galli S
CrabappleMalus spp. S
Dakota Pinnacle® BirchBetula platyphylla ‘Fargo’S
HackberryCeltis occidentalis S
IronwoodOstrya virginiana S/Psh
Japanese Tree Lilac Syringa reticulata S
Kentucky CoffeetreeGymnocladus dioica S
MN Strain RedbudCercis canadensisS/Psh
Northern CatalpaCatalpa speciosaS/Psh
Summertime™ Maackia Maackia amurensis ‘Summertime’S
Thornless HoneylocustGleditsia triancanthos var. inermis S

Deciduous Shrubs
Common NameScientific NameExposure*
BearberryArctostaphylos uva-ursi S
Black ChokeberryAronia melanocarpaS/Psh
Bush HoneysuckleDiervilla spp.S/Psh
LilacSyringa spp.S
Common Ninebark Physocarpus opulifoliusS
ForsythiaForsythia spp.S
Gray Dogwood Cornus racemosa S/Psh
Gro-Low Fragrant SumacRhus aromatica ‘Gro-Low’S
Hedge CotoneasterCotoneaster lucidus S
Japanese BarberryBerberis thunbergiiS
Korean BarberryBerberis koreanaS
Nannyberry ViburnumViburnum lentagoS/Psh/Sh
Potentilla Potentilla fruticosaS
Rugosa RoseRosa rugosaS
Tiger Eyes® Sumac Rhus typhina ‘Bailtiger’S

Evergreen Trees & Shrubs
Common NameScientific NameExposure*
Austrian PinePinus nigraS
Chinese JuniperJuniperus chinensisS
Common JuniperJuniperus communisS
Creeping JuniperJuniperus horizontalisS
Eastern Red CedarJuniperus virginianaS
Eastern White PinePinus strobusS
Jack PinePinus banksianaS
Red PinePinus resinosaS
Savin JuniperJuniperus sabinaS
Swiss Stone PinePinus cembraS
White SprucePicea glaucaS/Psh

Herbaceous Perennials
Common NameScientific NameExposure*
AsterAster sppS/Psh.
Black-eyed SusanRudbeckia hirtaS
Butterfly weedAsclepias tuberosaS
CatmintNepeta x faasseniiS
CranesbillGeranium spp.Psh/Sh
DaylilyHemerocallis spp.S/Psh
False Blue IndigoBaptisia australisS/Psh
GayfeatherLiatris spp.S
Globe ThistleEchinops ritroS
HostaHosta spp.Psh/Sh
Lamb's EarsStachys byzantinaS/Psh
Little BluestemSchizachryium scopariumS
PasqueflowerPulsatilla patensS
PeonyPaeonia lactifloraS
PrimroseOenothera spp.S
Russian SagePerovskia atriplicifoliaS
SalviaSalvia nemorosaS
StonecropSedum spp.S/Psh
WormwoodArtemisia spp.S/Psh
Prairie DropseedSporobolus heterolepsisS

* S=Sun Psh= Part shade Sh=Full shade

For more information on drought-tolerant plants visit Perennials in Water-Wise Landscapes (pdf) and Tough Trees and Shrubs for Tough Sites.

art8-4_600.jpg
art8-3_600.jpg
art8-2_600.jpg
Photo 2: Tiger Eyes® Sumac. Kathy Zuzek

Photo 3: Butterfly weed. Kathy Zuzek

Photo 4: Swiss stone pine. Kathy Zuzek

Here Today Gone Tomorrow - spring leaf spot diseases make a short visit to Minnesota

art9-1_600.jpg

Michelle Grabowski, University of Minnesota Extension Educator


For most areas of Minnesota, the spring of 2009 has been an unusually dry one.  This cool dry weather has kept many of the spring leaf spot diseases of trees at bay.  Diseases like anthracnose on oak, ash and maple have been absent up until the most recent wet weather.  Anthracnose is now being reported, especially in areas that received significant recent rain like southern Minnesota. The fungi that cause anthracnose, however, may not be causing problems for long. Anthracnose fungi thrive in cool wet weather and with the recent onset of hot temperatures, the growth and spread of this disease is likely to slow down.




Photo 1: Oak anthracnose. Michelle Grabowski


The biology of these fungal leaf diseases explains why in some years anthracnose is a big problem and in other years only minor damage occurs. Anthracnose fungi survive Minnesota’s winter in infections on twigs, buds, and last year’s infected leaves.  Spring rains splash spores from these infections onto newly developing leaves. These spores cause irregular brown leaf spots often centered on leaf veins. Since the infections occur on young developing leaves, it is common to see curling or distortion of the leaf tissue as parts of the leaf continue to grow, while others are halted by the anthracnose infection. If severe infection occurs, leaves may drop off the tree prematurely.


art9-2_600.jpg

Photo 2: Ash Anthracnose. Michelle Grabowski


If cool wet weather occurs throughout spring months, the anthracnose fungi thrive and disease can be quite severe. This year, wet weather did not arrive until late spring. Some anthracnose is occurring on oak and ash trees, but the leaf spots are fairly minor and mostly restricted to a few lower shaded leaves. In contrast, more significant leaf browning has been noticed in maples. 


Oak anthracnose is caused by the fungi, Discula quercina. Ash anthracnose is caused by the fungi Discula fraxinea. Both of these fungi primarily infect young developing leaves or wounded leaves. Once oak and ash leaves reach maturity, they are relatively resistant to the fungi. It is likely that less disease is being reported on these two trees because the wet weather that favors these fungi did not occur until the majority of the leaves were fully expanded and therefore somewhat resistant. For plant disease to occur, the pathogen, the susceptible host plant and the right weather conditions must all occur at the same time or disease will not develop.


art9-3_600.jpg

Photo 3: Maple Anthracnose. Michelle Grabowski


There are several different fungi that cause anthracnose in maple including Discula umbrinella, Discula campestris and Aureobasidium apocryptum. Less is known about the biology of these fungi. They result in similar browning and curling of leaves and can even blight young shoots. Like oak anthracnose and ash anthracnose new infections often form in response to wet weather. Unlike anthracnose on oak anthracnose and ash anthracnose, the fungi that cause maple anthracnose have been reported starting new disease from late spring through late summer. Anthracnose on maple seems to be the most common of the three diseases this spring. 


Although a tree heavily infected with anthracnose can appear ratty, this disease is not a serious threat to the health of the tree. Often leaf spots are limited to the lower shaded leaves.  The majority of the tree’s canopy remains green and can provide energy to the tree through photosynthesis all summer long. Even in years when anthracnose is severe and leaf loss occurs, trees create a new flush of leaves early enough in the year to avoid serious harm.


Poplar and Willow Borer

art10-1_600.jpg

Jeffrey Hahn, Asst. Extension Entomologist


All species of willow, most poplar (but rarely quaking aspen), and occasionally birch and alder are susceptible to attack by the poplar and willow borer, Cryptorhynchus lapathi.  This insect, a type of weevil, is 5/16 - 3/8 inch long with a slender snout as long as its head.  It has a roughly textured black body with mottled cream to tan colored patches on its body and its legs, including the back 1/4 of its wing covers.




Photo 1: Poplar and willow borer. Jeff Hahn


Poplar and willow borers overwinter as larvae in small cavities they excavate under the bark.  The larvae continue feeding in the spring, expelling frass (a mixture of sawdust and excrement) out of openings as they tunnel around stems or branches.  They eventually pupate in June and then emerge as adults in late July or August.  Adults feed on young stems, laying eggs in slits in the bark.  The larvae tunnel under the bark, creating galleries in all directions.  They chew exit holes in order to push the frass out.


art10-3_600.jpg

Photo 2: Poplar and willow borer damage. Mike Ostry, USDA Forest Service, Bugwood.org


These borers commonly attack trees between 1 - 4 inches in diameter and are particularly common on the lower trunk, especially near the root collar.  Their tunneling can result in irregular splits, cracks, and dead patches on the bark and around exit holes.  Stems can become deformed and some trees may become bushy due to epicormic sprouting.  Extensive tunneling can cause small stems or branches to die or break.  Damage is most severe on newly planted trees and nursery stock. 


Management can be challenging.  Remove and destroy infested stems.  This is most effective if there is not a lot of susceptible trees in the area and poplar and willow borer populations are relatively low.  You may be able to kill or remove larvae in their tunnels by poking a wire into holes (the larvae are active in the tunnels where the frass is being expelled).  Another option is to treat trees with a residual insecticide, such as permethrin, when adults are first active during late summer.


  • © Regents of the University of Minnesota. All rights reserved.
  • The University of Minnesota is an equal opportunity educator and employer. Privacy