|Yard & Garden Line News
Volume 5 Number 10 July1, 2003
Interested in Improving your Horticultural Knowledge and Skills?
James Calkins, M.Ag Program coordinator
The University of Minnesota's Department of Horticultural Science, in cooperation with the College of Agricultural Food and Environmental Sciences, offers a professionally-oriented master's degree that you might want to consider - the Master of Agriculture in Horticulture degree.
The Master of Agriculture in Horticulture (M.Ag.) is a 30-credit master's degree program that offers an individualized approach for further learning and the preparation of horticultural professionals. The program emphasizes integrated professional competence in the application of knowledge and the management of science and technology to advance horticultural expertise and the horticultural profession. Analytical and creative thinking, problem-solving, and real-world applicability and decision-making are also key aspects of the program.
The M.Ag. degree is designed for a varied audience with interests in horticulture. It may be used to advance the knowledge, expertise, and skills of individuals already employed in the field of horticulture or to provide the horticultural knowledge base needed by others interested in beginning new careers, starting their own business, or simply furthering their personal interests in the field of horticulture. The degree is based on a solid foundation of contemporary horticultural knowledge, yet is flexible and allows students to focus on the specific skills and objectives they need or desire.
Specific areas of interest might include:
• Enterprise/Production Horticulture - for those interested in the production and marketing of horticultural crops including nursery and landscape, turf, vegetables, floriculture, Christmas trees, or fruit and nut crops.
• Landscape and Garden Design - for those interested in the design and implementation of unique, aesthetically pleasing, horticulturally sound gardens and landscapes.
• Turf and Landscape Management - for those interested in the management of home lawns and landscapes, golf courses, athletic fields, corporate grounds, and parks.
• Public Horticulture - for those interested in applications involving arboreta, botanic gardens, zoological gardens, public gardens and schools.
• Restoration and Low-Impact/Low-Input Horticulture - for those interested in designing, developing, restoring and/or maintaining "natural" landscapes and gardens.
• Sustainable Horticulture/Agriculture - for those interested in sustainable horticultural production and landscape and garden management practices.
• Insects and Insect Pest Management - for those interested in nursery inspection, invasive species management, or insect pest management in production nurseries, greenhouses, parks, botanical gardens/arboreta, garden centers, indoor/outdoor landscapes, zoological gardens, and urban forests.
Additional areas of interest could include horticultural marketing or education, horticultural therapy, urban horticulture, or horticultural writing and/or illustration. Or perhaps you have a different idea or focus; a Master of Agriculture in Horticulture degree program can be designed for you too.
Minimum preparation required for admission into the program includes a bachelor's degree and knowledge of introductory, college-level concepts of algebra, chemistry and biology, botany, or plant propagation. Those lacking experience in these areas may complete the prerequisites through the University's College of Continuing Education or equivalent coursework at other institutions.
If you are interested in expanding your horticultural knowledge base and expertise, for whatever reason, the Master of Agriculture in Horticulture degree program may be just the ticket. Regardless of your background, we are dedicated to working closely with you to get you started and design a program that achieves your specific goals and objectives in the field of horticulture.
No Minnesota institution has a more knowledgeable staff or provides a stronger education in horticulture than the University of Minnesota, Department of Horticultural Science. We look forward to working with you as you pursue your interests in the field of horticulture.
For more information about the Master of Agriculture in Horticulture degree program or to request an application contact: Jim Calkins, Department of Horticultural Science, 1970 Folwell Avenue, St. Paul, MN 55108; (612) 624-9231; email@example.com.
Enjoy Fresh Flowers From Garden and Landscape Plants
Deborah Brown, Extension Horticulturist
As you assemble fresh bouquets for your table, bear in mind that many of our woody landscape shrubs yield stems with lovely flowers, berries, or seed structures that may be mixed with stems of blossoms from the garden. In fact, combining them with flowering annuals and perennials can help you achieve spectacular results. If you just remove a stem here and there, your shrubs will look none the worse for wear, and you will have greatly expanded your cut flower possibilities.
Treat stems from shrubs the same as you would other flower stems you pick for bouquets and arrangements. Cut them early in the day while temperatures are cool and they're not moisture-stressed. Ideally you'd take a bucket of clean, lukewarm water into the yard with you, so you could stick them into water immediately.
Once indoors, strip off any leaves that will sit in water once you transfer them to a vase. Shorten each stem to the length you want. If possible, hold the stem under water as you slice it. Use a sharp knife to make a clean diagonal cut; scissors may constrict the moisture conducting tubes in the stem, restricting further water uptake.
Place the stem – along with other cut flowers – in a vase filled with slightly warm water to which you've added floral preservative. You can buy the preservative in powdered or liquid form. Either way, it usually adds several days to the life of your bouquet or floral arrangement. Then set the flowers in a relatively cool location, out of direct sunlight..... and accept the compliments that are sure to be forthcoming.
Asian Longhorned Beetle Update
Jeff Hahn, Assistant Extension Entomologist
Asian longhorned beetles have been a significant problem in the U.S. since they were found in New York in 1996. They are believed to have been brought into the U.S. in pallets or packing crates from China. They have a huge potential to spread and become established in the U.S.
Asian longhorned beetle.
Photo credit: USDA Forest Service
They are a problem because they attack and kill trees. They infest unhealthy trees which is typical of longhorned beetles but they also attack healthy ones as well which is not typical of this group of beetles. Asian longhorned beetles prefer maples but are also known to infest many other trees, including alders, birches, elms, horsechestnut, poplars, and willows. Less susceptible trees that are being used for replanting include gingko, hackberry, basswood, little leaf linden, honeylocust, Kentucky coffeetree, and oaks (white, bur, swamp white),
Asian longhorned beetles are large, robust insects. They measure from 3/4 inch to 1 1/4 inch long and are black with white markings. They have very long antennae, about two inches long, with conspicuous black and white banding. Their also have blue tarsi (feet).
Not every big blackish beetle with white spots and long antennae is an Asian longhorn beetle. In fact we commonly encounter another longhorned beetle called white spotted sawyer. It is a little smaller than the Asian longhorned beetle with less conspicuous spots (the white marks appear more mottled than as distinct spots). It also lacks the black and white banding on the antennae and blue tarsi (feet).
White spotted sawyer.
Photo credit: Jeff Hahn
Asian longhorned beetles are thought to have one generation a year in the U.S. Adults are present from May through October. When they emerge, they create a large (3/8th inch), round exit hole. Also look for shallow pits that females chew out of the bark to lay eggs. Asian longhorned beetles oviposit virtually anywhere on the trunk, branches (as small as an 1 1/4 inch) and even exposed roots. The larvae feed under the bark, girdling the tree. Infestation causes dieback and eventually kills the tree.
When these borers are discovered, the area is quarantined and every effort is made to eradicate them. The only effective control is to cut down and destroy infested trees. So far, Asian longhorned beetles have only been found in the landscape in New York (first found in 1996), Chicago (first found in 1998), and New Jersey (first found in January, 2003). They have also been intercepted in warehouses in California, Florida, Illinois, Indiana, New Jersey, New York, North Carolina, Ohio, Pennsylvania, South Carolina, Texas, Washington, and Wisconsin.
Photo credit: USDA Forest |
Although neither New York and Chicago have eradicated Asian longhorned borers from their landscape they have greatly reduced the number of infested trees. In New York, 144 Asian longhorned borer infested trees were discovered last year compared to a high of 1,220 infested trees in 1996. In Chicago, only 4 infested trees were found last year (in the Ravenswood area) compared to a high of 911 in 1998.
So far, Asian longhorned beetles have not been discovered in Minnesota. However, there are many susceptible tree species in the state and Asian longhorned beetle would undoubtedly thrive here if it were introduced. Successful eradication of this beetle depends on early detection. The sooner it is found, the sooner steps can be taken to eradicate it. If you find an insect that you suspect is an Asian longhorn beetle or believe you have a tree infested by this beetle, contact the Minnesota Department of Agriculture at 651-296-6684 or 1-888–545-6684.
For more information, see the USDA Forest Service Asian Longhorned Beetle home page, http://www.na.fs.fed.us/spfo/alb/.
Insect in Lawns
Jeff Hahn, Assistant Extension Entomologist
There are generally not a lot of different insect problems found in home lawns in Minnesota. White grubs is the most common insect pest we encounter. We also commonly see nightcrawlers (a type of earthworm) as well as ground nesting ants and an assortment of other less frequently seen insects, including sod webworms, cutworms, and greenbugs (a type of aphid). Recently, there have been several interesting reports of insects associated with turf that we do not normally see.
Photo credit: Jeff Hahn
In two reports in the Twin Cities, ‘worms' were found associated with turf that were not actually injuring grass. In the first case, insect larvae were found with leaves that were recently raked from a lawn, occurring in the ‘zillions'. They were concerned about what kind of damage they could cause to plants. The insects turned out to be a type of beetle larva. Although they were difficult to identify exactly they seem to be related to sap beetles (nitidulid beetles) or pleasing fungus beetles (erotylid beetles). Although we did not have a lot of information, these insects seemed to be either feeding on fungus or decaying organic matter and were not harmful to turf or other plants.
This general scenario was repeated when we received turf samples containing 1000's of ‘worms'. They were found near the edging surrounding a tree and its mulch. The owner was less concerned about the turf as he was about the potential damage the insects could cause to the tree. Again, it was difficult to identify the insects exactly but they appeared to be wood gnats (anisopodid flies) or something very closely related. It was never clear how so many insects ‘just appeared' in their turf but it seemed very likely that they were associated with the adjacent mulch either feeding on decaying organic material or fungi.
There have also been some sightings of bronzed cutworms in home lawns which is rarely seen (they would be common in golf courses). One report from Cloquet described numerous, small (4 inch diameter) brown spots in the lawn and scores of cutworms. Bronzed cutworms do not normally survive winters in Minnesota but are brought up by air currents during the summer. However, there is evidence that some cutworms survived the winter as larvae were seen as early as April. Bronzed cutworms can have more than one generation in a year so management would be appropriate to reduce damage in your lawn. You can physically destroy them, e.g. when they move to the surface at night, run a lawn mower over them. If you are interested in using a less toxic product, apply parasitic nematodes, such as Steinernema. Or an application of a residual insecticide, such as permethrin, would also effectively kill them.
Marlin Rice, Iowa State University
Get the low down on this month's insect pests at
The Dilemma of Foliar Disease
Janna Beckerman, Extension Plant Pathologist
The recent epidemic of foliar disease problems has underscored the Achilles heel of plant pathology: If the symptoms are readily observable, it is usually too late for effective treatment for that year. The simplest part of managing the disease is diagnosis. Unfortunately, many homeowners are unsatisfied with a wait and see approach. It is important to stress that fungal leaf diseases generally do not require chemical treatments because they usually are not life threatening. Unfortunately, the satisfaction of providing the correct diagnosis is usually cut short when the owner asks what they can do to "cure" the problem. Although most homeowners are greatly relieved that the foliar problem will not kill the tree, they often feel the need to do something. In providing management options, too often I am told that managing the problem next year was not soon enough.
Note reduced size of leaf with severest infection. Healthy leaf received adequate fungicide coverage.
Remember the Disease Triangle!
In order for disease to occur, a susceptible host must come in contact with a virulent pathogen. The environmental conditions must favor this occurrence. In order for spores to germinate the foliage must remain wet for several hours. Cool, moist weather (usually spring, but autumn, too) is ideal for fungal leaf-disease development. Although you cannot control the weather, watering so that the foliage becomes wet in the early evening, maintaining dense plantings, or otherwise inhibiting airflow all favor disease development. Whenever possible, water in the morning to allow leaves to dry during the day. Prune plants to increase airflow and allow better air circulation.
Although it is strongly recommended, raking fallen leaves will not eliminate all the infected leaves from a property. And don't forget your lazy neighbors who never rake! Many fungal foliar diseases overwinter in the buds and twigs that remain in the tree, so raking may have a minimal effect on the level of spore production. If your tree has become severely defoliated three times in five years, or has begun to become defoliated twice in one year (this means the tree has re-leafed, and been re-infected so severely that defoliation has begun for the second time) chemical treatment is in order.
It is important to reiterate that treatment of many fungal leaf diseases and needlecasts is with fungicides containing active ingredients of copper, chlorothalonil and sulfur, to name but a few. Because they are protectants, you must maintain the chemical barrier between the leaf and the fungus. This translates into repeated applications, usually 7 to 10 days, from bud break for deciduous trees through leaf elongation. For conifers, the same holds true from bud break through the formation of the candle. Typically, two to three applications are needed, although more may be necessary if cool, moist conditions persist into the summer.
The primary difficulty in managing foliar diseases is due to timing. This is where knowledge of the pathogen's life cycle becomes so important. Identifying the disease provides you a place start. Although fungi are among the most common agents of foliar disease, it is important to remember that they are not the only agents of foliar disease. Always confirm your diagnosis, either through the Yard and Garden Clinic, or the Plant Disease Clinic. Upon identifying the pathogen, refer to Plant Pathology by George Agrios, or Diseases of Trees and Shrubs by Sinclair et al. In addition to helping you confirm your diagnosis, both authors explain the lifecycles of the pathogens. Because most fungicides available for home use are protectants, they have little to no effect after the fungus has entered and established itself in the plant. Protectants work to create a barrier or protective shield that prevents the fungus from either germinating, or penetrating the plant tissue. If a large fraction of your leafy tissue is already infected, spraying a protectant fungicide will have little to no effect.
To understand the science of fungicide applications (the when and how often of application) it is imperative that you understand the foliar disease pathogens. Fortunately for us, most (but not all-remember that a correct diagnosis is essential!) foliar disease pathogens are members of the fungal class Ascomycetes. This means that the "typical" life cycle starts in the spring. Spores (either sexual or asexual) are produced from fruiting structures that have overwintered on dead, leaves or twigs. These spores become rain splashed or air-borne and infect young, succulent leaves. Because this foliage is actively growing it is the most susceptible to disease. The spore adheres to leaf, germinates and penetrates the leaf, or even twig tissue. As the fungus continues to grow, it will produce fruiting structures on the infected leaves. If conditions are cool and moist, a secondary cycle can develop and exacerbate the disease problem. Such conditions occurred this year. As summer develops, most leaves harden off and the infections abate. In autumn, the infected leaves fall and the cycle repeats itself next spring. Because most fungicides are protectants, summer applications for control of leaf blister or anthracnose are ineffective because no new infections are occurring. If you begin treating with fungicides in the late spring or early summer when the symptoms appear, it's too late.
But what if you are prepared for next year? If defoliation was severe and fungicide use is warranted, we encounter the secondary source of difficulty that is due to the extensive spray schedule most fungicides require in order to be effective. Most of these fungicides need to be applied at bud break, with follow up from anywhere between 7 and 21 days. Failure to follow up with a secondary treatment may enable another "flush" of spores to infect. However, if fungicide treatments are limited to only one or two sprays in the spring and cool, wet conditions persist into the summer, the continued growth of the tree, coupled with the extended sporulation of the fungus means that the disease may still develop. This phenomenon occurred this spring.
A second class of fungicides is the systemics. Systemic fungicides are absorbed and translocated (move) through the site of application throughout the plant. Because they are absorbed, they are not as subject to wash-off by rain as the protectant fungicides. They are often more specific for managing fewer fungal diseases. They may be protective, or curative and often give longer control than the protectant class. Systemic fungicides, if applied soon after infection, are capable of penetrating the leaf and stopping further development of the fungus, thus preventing symptom development. However, few are available for use by homeowners and require a certified applicator to apply these pesticides.
The proper timing of any pesticide spray requires recognition of climatic conditions. Fungicides can be "magically" turned into herbicides if applied during hot weather. These reactions, referred to as "phytotoxic," can cause more damage than the disease you were treating. Other concerns include drift into nearby gardens, or plants that are contraindicated for spraying with the fungicide in question (for example, certain apples respond very poorly to contact with fungicides containing the active ingredient Azoxystrobin; viburnum, currants and gooseberries are often referred to "sulfur shy."). Fungicides can be quickly washed away, or never adhere if the foliage is wet.
At this point, you have correctly identified the fungus, identified the proper management strategy, decided that fungicides played a role in this strategy, identified your fungicides and even when to spray. And you aren't even finished yet. The final problem that needs to be faced is the issue of proper coverage. Although young trees, small trees and shrubs can be easily and properly sprayed by a home applicator, most home applicators are not equipped to spray mature, two story trees with fungicides and realistically obtain the coverage necessary to prevent infection . Not only is it difficult, but it may need to be repeated. This is when a licensed tree care professional is needed.
Although foliar diseases are ugly, they are rarely fatal. For this reason, fungal foliar diseases do not usually require chemical treatments. Avoid the impulse to "spray and pray" at the first appearance of leaf disease. Correctly identify the disease-causing agent and determine the potential damage to the tree's health versus the damage to its appearance. Although it's too late to do much right now, now is the time to develop your management strategy for next spring!
Apple Scab: A selected bibliography
Beth Jarvis, Yard & Garden Line
Apple scab has been the pathogen of the week for weeks. It's a fungal disease that may cause apple leaves to turn yellow and drop off. The long, wet spring gave the fungus a rollickingly good start and it has affected even resistant cultivars. (Resistant doesn't mean immune. If there's enough inoculum of a viruent pathogen, in a conducive site, resistant plants may develop the disease.)
Here's a reading list of Yard & Garden publications on apple scab.
Yard & Garden Line News, June 15, 1999 :
Yard & Garden Line News, June 15, 1999 :
Yard & Garden Brief on apple scab :
Yard & Garden Line News, June 1,2001, Choosing Ornamental Crabs:
Yard & Garden Brief on apple scab resistant crab apple trees:
July Garden To-Do List
Beth Jarvis, Yard & Garden Line
We've had requests for a garden check list. This is not all inclusive, but it's a start.
Compiled from conversations with: Bob Mugaas and Doug Foulk, Metro area Extension educators; Gary Johnson, Urban Forestry and the Y & G Clinic staff.
*Deadhead peonies--cut the faded flowers off. You might save a few seedheads for flower arrangements.
*Deadhead annuals such as geraniums, petunias and cosmos to extend the bloom.
*Renovate strawberry beds as soon as June bearing plants are done producing. For how to see:
*Once summer raspberries are done producing berries, renovate those by pruning out canes that fruited this summer and narrowing rows. For help with that, see: http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-Aug0199.html#ryrenov
*Start treating for apple maggot--by bagging the fruit, putting out sticky traps or starting a spray program. See the apple maggot sheet at: http://www.extension.umn.edu/distribution/horticulture/DG1007.html
The organic, chemical free bag option can be found here: http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-Feb0102.html#apples
*Check out current insect pests on Jeff's web pages:http://www.extension.umn.edu/projects/yardandgarden/EntWeb/currentpests.html
*Tree canopies are at their fullest and densest. Now is a great time to pay attention to how much light various parts of your landscape actually get. This will help you pick plants that will thrive in those areas.
*Maintain a 3-3 1/2" mowing heigh when cutting grass. Longer blades shade the soil, protect the grass crowns and reduce water loss.
*Cool season turf grasses grow slowly in hot weather. It's best to wait until mid August to fertilize. If you wish to ferrtilize now, use something with at least 50% of the nitrogen in a slow release form. Too much fast release nitrogen stresses the grass.
*Avoid herbicide applications during warm weather; you'll get a more effective weed kill in the fall.
*If you reduce lawn watering, do it gradually. On lower maintenance lawns, rather than an inch a week, you can cut back to a half inch every weeks.
*Leave dethatching/vertical raking and aerifying until fall.
*See info on current problems at Janna's pages: http://www.extension.umn.edu/projects/yardandgarden/PlantPathWeb/Plpa.htm
Trees and Shrubs:
*Stop fertilizing woody plants after mid-July. They need to start hardening off to survive next
This is NOT renovation
*We're entering the low risk period for pruning oak trees. If you wish to remove an annoying branch, do so but paint the fresh wound immediately with latex paint or shellac.
*Mulch trees and shrubs to help retain soil moisture. Mulch can be piled 3"-4" high but leave two inches of space between mulch and the tree bark.
*Don't forget to water young trees during dry spells.
*Rejuvenation prune spring flowering shrubs, such as lilacs and mock orange by removing 1/3 of the thickest stems down to the ground.
*Critically evaluate landscape trees for weak branch attachments, multiple leaders and inspect for decay. Storm damage can be prevented by corrective pruning. A certified arborist can advise on injured trees.
Info on pruning is at:
Info on hiring an arborist:
*Identify hazard trees before they fall down:
*As summer veggies start to bear--side dress with fertilizer. Read about garden fertilizer at: http://www.extension.umn.edu/distribution/horticulture/components/1731-26.html
*Cage or stake tomatoes if you haven't done so before. It keeps them healthier and more productive: http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/H237trellis.html
*Septoria leaf spot may begin about the time tomatoes start setting fruit. Read all about it at:http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/p232septoria-tomato.html
*Mulch tomatoes with straw, dried grass or partially decomposed compost to reduce weeds and maintain even soil moisture.
*Stop harvesting rhubarb and asparagus now (July 1). Let plants grow the rest of the summer to recharge for next year.
Heliotrope is one of my favorite garden annuals, so I thought I add it here. It's an easy to grow, full sun annual.
Next issue, we'll talk about pesticide spraying. Every year, we hear about neighbors who spray stuff that lands on other peoples' tomatoes, etc. So, we'll look at being a good neighbor with tips for you, or your neighbors.
In the future, you'll also get to meet Dr. Tim Kurtti, who does deer tick research. And, my friend and colleague Cindy Tong, who is a post harvest physiologist, and I will visit the St. Paul Farmers' Market in search of exotic Asian edibles. We will attempt to identify and demystify the veggies you might use if you knew what they were! In a bit, we'll hear about the closest thing we have to Japanesese maple.
Sweetly fragrant heliotrope.
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.
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