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Friday, April 30, 2010

Japanese Beetles in Minnesota: Education, detection, and management

Dan Miller, Plant Health Specialist, University of Minnesota Landscape Arboretum

JB Image.jpg
Japanese beetle
Forestry Images. Russ Ottens, University of Georgia.
The Japanese beetle (Popillia japonica) was first detected in the United States in New Jersey in 1916 and has spread throughout most states east of the Mississippi and to parts of Arkansas, Missouri, Kansas, Oklahoma, Iowa, and Minnesota west of the Mississippi. In Minnesota, the beetles were first detected in 1968. Trapping programs conducted by the Minnesota Department of Agriculture (MDA) showed low but consistent numbers from 1991 to 1998. Trapping data in 1999 and 2000 showed a dramatic increase in Japanese beetles with the highest counts occurring in Washington, Ramsey, Hennepin, Dakota, and Carver counties. After trapping in 2002, the MDA concluded that the beetle was too widespread to be eradicated. The beetle was then deregulated and budget cuts shifted the direction of the program so the statewide trapping program was discontinued.

Arboretum exhibit demonstrates integrated control of Japanese Beetles

In recent years, Japanese beetle infestations have become more noticeable in the metro region with many reported cases of damage to golf courses from the white grub larvae feeding on grass roots and damage to ornamentals shrubs and trees (especially roses, grapes, and lindens) from adult beetles. It is apparent that awareness of the pest is growing; however many home gardeners are not experienced or knowledgeable regarding integrated control strategies for the pest. In 2009, the Minnesota Landscape Arboretum obtained a grant from the North Central Integrated Pest Management Center to create an exhibit at the Arboretum to provide updated, relevant IPM information to the public on environmentally safe ways to control the adults and larvae of the Japanese beetle. The display featured a sign located in the center of a plot of turfgrass and roses with general IPM information, a take-home brochure with more detailed information, and a terrarium so visitors could observe the beetles while they were feeding on plants.

Determining the distribution of Japanese Beetle in Minnesota

A secondary part of the grant involved a survey to determine the current statewide distribution of the beetle. In August 2009, an electronic survey was sent to over 300 golf course superintendents via the Minnesota Golf Course Superintendents Association. In October a second electronic survey was sent to nurseries throughout the state via the Minnesota Nursery and Landscape Association. These surveys provided links for respondents to use in properly identifying the beetle. The survey also asked if beetles or grubs had been observed on their golf course or nursery, when they were first observed, the damage levels, and the control strategies employed. Additionally, over 40 University of Minnesota Extension Educators and Master Gardeners across the state were contacted by phone and asked if they had heard of infestations in their areas. Based on previous trapping surveys by the Minnesota Department of Agriculture and our 2009 consensus surveys, it is apparent that the beetles are primarily located in the seven county metro area and southeast toward Rochester and west toward Mankato (Figure 1). Future IPM control efforts should be focused in these areas.

Even though Japanese beetles have been present in the metro area for several years, they were not observed at the Arboretum until 2007. To get a better understanding of the encroachment of Japanese beetles to the Arboretum, a trapping study was initiated in 2009. Twenty traps were set on golf courses and parks in an approximately 10 mile radius round the Arboretum and compared to traps on the Arboretum grounds. Traps were set in each location once a week, left for 24 hours, retrieved, and beetles were counted. Trapping started on July 17th and continued for ten weeks until September 16th. The most remarkable outcome of this trapping project was the noticeable difference between trap counts on golf courses east of the Arboretum and golf courses west of the Arboretum. The average number of beetles per trap for the four golf courses east of the Arboretum was 483.0 while the average number for the two eastern courses was only 2.6. The average number of beetles for the Arboretum's traps was 5.7. Several golf course superintendents indicated that 2009 was either the first year or the second year that they were aware of the beetle's presence. It appears that the Japanese beetle populations are increasing and are continuing to advance further west.
Status of the Japanese Beetle in Minnesota in 2009
(PDF available)

Methods for decreasing potential damage from Japanese Beetles

Homeowners and golf course superintendents in the metro and southeastern region of Minnesota can decrease potential damage to their ornamentals and turfgrass by scouting and early detection.
Golf courses (and other turf managers) should concentrate their control efforts on the grubs if turf damage is considerable. Imidacloprid and Acelepryn (a reduced-risk insecticide) have proven to be effective.

Homeowners can control small infestations of adult beetles by picking them off the plants and dropping them into soapy water or rubbing alcohol. Pheromone traps are not recommended as beetles may miss the trap and land on nearby landscape plants, causing damage.

If damage is beyond tolerable levels, conventional insecticides may become necessary. Imidacloprid and residual pesticides like pyrethroids are effective for adults but should only be used where infestations are found and not used as preventative treatments.

Homeowner's can treat grub damage using biorational control with products containing halofenozide an insect growth regulator or with beneficial nematodes. It is necessary to confirm that turf damage is caused by white grubs and not by other turf diseases before implementing control methods.

Detection of Japanese Beetles in new counties

If beetles are found in counties not marked on the map in Figure 1, please let us know by sending specimens including capture location and date to Jeff Hahn at Department of Entomology 236 Hodson Hall, 1980 Folwell Ave., St. Paul, MN 55108 or send digital images to

May 2010 Garden Calendar

Contributors: Karen Jeannette, Yard and Garden News Editor
Including Excerpts from the 2010 Minnesota Gardening Calendar

This month Bob Mugaas tells us the crabgrass has emerged early (Home Lawn Care - Recapping the very early spring of 2010 and what's next for timely information about Lawns) and Jeff Hahn says Spring Insects are Early this year, too. Gardeners across the state have been inquiring if they can plant and perform other garden and yard tasks earlier than in past years. Below we provide advice for this gardening season come early.

Advice for the Gardening Season Come Early

When to Plant Flowers

Despite the warmer and earlier growing season, the answer to, "Is it safe to plant perennials and annuals?" is still "Wait until mid-to late May to plant perennials and until after your area is frost free before planting flowering most annuals."

Why Wait?  In most Minnesota locations, perennials can be planted after mid-month, but wait until you're certain there will be no more frost before adding flowering annuals to the garden. Most, including impatiens and geraniums, have no frost tolerance. Pansies, violas, and johnny jump-ups are among the few annuals that will not be killed or badly damaged by frost. Calendulas, snapdragons, and sweet alyssum may also be planted a little early. 

You can identify when your area is likely to be frost-free using the MN spring frost-free map:  

When to Plant Vegetables

Kale and other cool season vegetables can be
planted as soon as the garden bed is ready.
Karen Jeannette
Which vegetables can I plant and when? You can sow early "cool-season" crops such as lettuce, cabbage, cauliflower, broccoli, Brussels sprouts, and onions immediately after preparing your garden plot.

Warm season vegetables, like tomatoes and peppers should be planted after the last chance of frost.  See "Planting the Vegetable Garden": for guidance on when to plant and how far apart to space your vegetables.

Keep Up with Early Pests and Diseases

Plant Diagnostic Modules: Pictures, simple descriptions, and easy to follow management instructions make it easy to stay ahead or just keep up with plant pests and problems using any of the University of Minnesota Garden Info Diagnostics Modules:
Stay ahead of disease this year with diseases management tips in this month's article by Michelle Grabowski: Keeping Plants Healthy and Green While Going Green

When to Perform Lawn Care

The lawn care calendar guide "Upper Midwest Home Lawn Care for Cool Season Grasses" ( is a helpful guide for scheduling lawn maintenance. However, this month, learn how to adjust your lawn maintenance practices for this earlier than normal growing season with Bob Mugaas' timely article, Lawn Care: Recapping the very early spring of 2010 and what's next for timely information.

For more information on lawn care, see the University of Minnesota Garden Info lawns section:


Are you starting a raised bed? Ordering soil? Adding Compost? Find information on soil topics at the University of Minnesota Garden Info soils section:

You needn't test your garden soil annually, but if plants have grown poorly the past year or two, despite being in a sunny location and receiving normal care, visit U of M Soil Testing Lab web site: .  You'll get a questionnaire with instructions on taking and sending in samples, If the problem is due to a nutrient imbalance, excess alkalinity, or acidity, they'll suggest a remedy, with respect to what you are growing.

Small Fruits

If you'd like to grow some fruit in your yard, but don't have room for apple or pear trees, consider planting Minnesota-hardy blueberries, raspberries, or strawberries. You need an area well-drained soil and plenty of sunlight -- a minimum of six to ten hours daily. More is better. In addition, blueberries need acidic soil to thrive. Have your soil tested for specific information on acidifying your soil before planting them. For more information regarding fruit varieties and culture, see the Fruits section of the U of MN Gardening Information website:


See the Extension listings of garden tours, horticulture diagnostic clinics, workshops, and plant sales @

Home Lawn Care: Recapping the very early spring of 2010 and what's next

Bob Mugaas, University of Minnesota Extension Educator

Snow mold recovery

This spring began with the very early snowmelt in mid-March that left in its wake one of the highest incidences of snow mold on many residential and commercial lawns in recent memory. Much of that could be attributed to the very wet snow that fell around Christmas time on unfrozen or barely frozen lawn surfaces. The high moisture content of the snow combined with the mostly unfrozen lawn conditions provided nearly ideal conditions for the snow mold fungi to grow and thrive. In addition, that snow cover was maintained throughout the winter months providing a very long period of total snow cover and good conditions for snow mold growth. However, as is often the case, even with as much snow mold as was evident this spring, most lawns will have recovered on their own and returned to healthy growth and good green color by early May. The severity of snow mold on some lawns did result in the need for some reseeding to fill in thin areas resulting from that injury. Photos 1 and 2 show a commercial site affected with snow mold earlier this spring that has now grown out of those symptoms without the need for reseeding or other repair. A light application of fertilizer and some watering as needed this spring will help further restore and invigorate those areas.

Photos 1 and 2: Snow mold infestation and turf recovery. Bob Mugaas

snowmold before and after.jpg

Meadow vole damage and recovery

That continuous snow cover over winter also created a good habitat for meadow voles to invade our lawns resulting in slight to extensive surface tunneling in lawns, especially those close to unmaintained grassy areas such as next to vacant lots, prairie edges or other nearby grassy areas where voles retreat to after the snow melts. See Photo 3 for typical injury associated with meadow voles in lawns. For the most part, these critters tunnel along the surface eating a variety of vegetative material including the grass. One may observe tunnels traveling over and through the lawn surface. It is often common to see loose grass 'clippings' mounded up over the tunnels creating a slightly raised appearance to the seemingly random tunnel patterns. While the grass foliage is eaten by the voles, the grass plant crowns (growing points) often escape being eaten and are responsible for the regeneration of new leaves and stems that ultimately fill in the tunneled areas. Since the plant is having to start from scratch in its spring regrowth, the tunneled areas frequently lag behind the rest of the lawn area in spring recovery but do ultimately catch up to the rest of lawn in terms of height and density. See Photo 4 of new grass shoots coming in a surface tunnel caused by voles. Again, a light application of fertilizer and water as needed will help restore the growth and vigor of these areas. In nearly all cases, recovery occurs without the need for reseeding or replacing the damaged areas.

Photos 3 and 4: Vole damage and indications of turf recovery. Bob Mugaas.


Early season mowing

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Photo 5: Turfgrass color variances associated with differing heights of growth prior to first mowing. Bob Mugaas.
By the writing of this article most of us have had to mow our lawns at least once or even twice already this season. In some cases, there appears to be areas of yellow or lighter green grass following mowing, especially the very first mowing of the year. See Photo 5. With the typical unevenness of that very early spring growth prior to the first mowing, it's not uncommon to see lighter areas intermingled with normal darker green areas. The lighter areas are usually associated with grass that had grown vigorously early and was taller than much of the surrounding grass. Hence, when its mowed at regular mowing heights, the grass ends up being cut back into lower blade and sheath tissue which is often lighter green to almost yellow due to the lack of chlorophyll. Cutting into that area of the plant is very stressful for the grass plant as it eliminates much of the leaf surface responsible for making the plant's food and can slow or even stop root growth temporarily until the plant can regrow sufficient tissue to resume normal growth. Grass that has not grown so vigorously or just grown more slowly ends up not being cut back so severely and hence retains its normal medium to dark green color and relatively uninterrupted growth. In most instances these early growth differences even out by the third or fourth mowing. Mowing higher rather than shorter, especially for the first cutting or two may help avoid cutting those taller areas too short initially while still being fine for the rest of the lawn area. This will also avoid the generation of excessively long and large amounts of clippings as also seen in Photo 5. When this quantity of clippings is generated from mowing, they should be removed or at least more uniformly dispersed over the lawn surface so as not to remain in large clumps, which can interfere with the healthy growth of grass plants underneath the clumps.

Crabgrass arrives early too!

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Photo 6: Crabgrass seedlings visible April 20, 2010 near a curbline in North St. Paul, MN. Bob Mugaas.
By the middle of April, crabgrass seedlings were already emerging in what are termed heat sink areas. These are areas that warm more quickly during the early part of the growing season and hence growth in these areas is usually well ahead of the majority of the main lawn areas. Examples include areas next to sidewalks, driveways, curbs, narrow boulevards, unprotected bare soil areas and the like. Usually the warming effect extends less than two feet from these paved areas back into the main lawn. Other exposed soil areas, especially those with south and west exposures generally warm more quickly than those covered with some form or vegetation or mulch. In addition, sandy soils tend to warm more quickly than heavier clay soils. Since drier soils are warmer soils compared to moist soils, the lack of early spring precipitation over much of the area caused soils to dry more quickly with the above average temperatures and sunlight. This also contributed to warmer than usual soils that in turn saw some of the earliest crabgrass germination in quite some time in the Twin Cities area. See Photo 6 of newly emerged crabgrass seedlings near a curb area.

Once crabgrass has emerged from the ground and is visible, it is too late to apply preemergence herbicides for crabgrass control. These products act on the newly germinating crabgrass seedlings prior to their emergence from the ground. In this case, one will need to use products containing the active ingredients quinclorac or fenoxaprop-p-ethyl. Both of these are available through commercial lawn care firms. Quinclorac can also be found in some homeowner lawn weed control formulations. Check the product label for its list of active ingredients. For very small infestations, it may be practical to manually remove them. In either case, treating the seedlings while they are still small and tender is much more effective than when plants are larger and more mature.

Just because you may have already observed some crabgrass germination in those heat sink areas, it doesn't necessarily mean you shouldn't apply a preemergent crabgrass control product to the rest of the lawn area if it's needed. However, it should be applied very soon, like within the first week or so of May, depending on your specific site conditions. Soil temperatures in the main lawn areas will lag behind those in heat sink areas, but they do catch up fairly quickly as temperatures continue to warm, especially overnight temperatures. Even though crabgrass germinates earlier in those warmer soils, it doesn't germinate all at once. Hence, an application of preemergence herbicide in those heat sink areas can help prevent later germinating seeds from getting started but won't kill those already sprouted.

Easy-does-it for spring fertilizing

Usually about the time the lawn is greening up and in need of its first mowing is a good time to consider applying a spring application of lawn fertilizer. For many of us, that time may have already passed. However, that doesn't mean it's too late to fertilize the lawn. In fact, sometime within the first three to four mowings of the year is still a good time to fertilize. Regardless of the situation, it's wise to not be aggressively fertilizing your lawn in the spring, especially with large amounts of nitrogen. That's best left for the late summer period.

In the spring, there is a natural, normal flush of growth by our grass plants. It begins with active root growth followed by rapid shoot growth. As shoot growth begins to accelerate, root growth tends to slow down. If too much nitrogen fertilizer is applied, shoot growth will be even more rapid resulting in a more frequent need for mowing but is also unhealthier for the grass plant. Excessive growth stimulated by too much nitrogen creates a more succulent plant that in turn requires greater amounts of moisture to sustain its growth. That increased succulence is more vulnerable to injury from summertime stresses and can be more prone to certain disease and insect infestation. The bottom line is, use moderate to low amounts of N in the spring to maintain balanced, but healthy, turfgrass growth. For more information on lawn fertilizing, see the publication Fertilizing Lawns (

Water if needed to support early season growth

While we often don't think of watering our lawns much before sometime in May, this year, due to the drier than normal conditions and earlier than normal vigorous grass growth, watering may be needed to sustain healthy, early season turfgrass growth. Early spring is the time of year when grass plants are actively growing new and deeper roots. That allows the plant to mine water and nutrient reserves from a larger soil volume, which, in turn, sustains the continued healthy growth of new shoots and roots. At this time of year watering deeply but infrequently is a good practice. Thus, an inch of water per week (or longer interval depending on weather conditions) including any rainfall that occurs will help keep soils moist and promote healthy root growth. If you have heavier, more clay-like soils where it takes a long time for water to infiltrate into the soil, it's usually best to apply a couple of lighter applications allowing time in between for the water to soak into the soil. Likewise, on lighter sandy soils that drain more rapidly, infiltration is not so much a problem as is the likelihood of water moving too quickly down through the soil and beyond the grass plant's roots and therefore not benefiting the grass plant. Hence, a split application of water will also be more beneficial for the grass on sandy soils.

While spring has indeed arrived ahead of most years, the tasks of lawn care remain much the same except that they need to be carried out earlier than many of us are used to. Paying attention to prevailing weather conditions and observing what's happening in your lawn are very valuable aids when it comes to understanding what's going on and what to do next.

Keeping Plants Healthy and Green While Going Green

Michelle Grabowski, University of Minnesota Extension Educator

Regardless of the time and effort put into a garden, inevitably at some point a plant disease will show up. These spots, rots and wilts can be quite distressing to a gardener working to beautify their yard or hoping for a fresh crop of fruits or vegetables. Often the first response to disease problems is to spray a fungicide. Many gardeners however are looking for alternatives to this management strategy. Whether you are going organic, trying to reduce the number of pesticides used in your yard or looking for a simple inexpensive means to reduce plant diseases, cultural control practices can be a great strategy for keeping plants healthy. The US Department of Agriculture Organic rule states that preventive and cultural control practices must be a grower's first choice for pest control. In yards and gardens, preventative and cultural control practices are often effective at reducing disease problems to a level where they are no longer a concern or eliminating them altogether. Combining several of the cultural control practices below can keep gardens healthy without the use of pesticides.

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Photo 1: Healthy basil plants.  M. Grabowski UMN Extension.
Purchase Healthy Plants - Do not accidentally bring plant pathogens into the garden on infected transplants or seed. Carefully inspect all transplants prior to purchase for disease symptoms like leaf spots, discolored areas on stems, leaves or roots. Above ground plant parts should be firm and green. Roots should be firm and light tan to white. Many root hairs should be present. Reject any plants with symptoms of disease. Purchase seed and transplants from a reputable source.

Disease Resistant Plants - Some plants are bred to be resistant to a specific disease. Whenever possible select varieties that have resistance to common diseases. Look for varieties that advertise resistance to specific disease problems like powdery mildew resistant pumpkins or apple scab resistant crab apple trees. General statements like 'good disease resistance' often imply a hardier plant, but these varieties may not include resistance to any specific disease problems.

Scouting and Diagnosis - Examine plants regularly throughout the growing season to find pest problems while they are still minor. Identify the pest causing the problem before taking action. Visit for help in identifying unknown pest problems. Knowing the identity of the pest will allow you to choose management practices effective against that particular pest.

Sanitation - If a plant disease problem is identified on a few leaves, stems or fruit, these plant parts should be promptly removed from the garden. Fungal and bacterial plant pathogens reproduce on infected plant parts. Removing infected plant tissue will reduce the growth and spread of the pathogen within the garden. Remember, never remove more than 1/3rd of a plants leaves. In some cases it is worthwhile to completely remove one severely infected plant to prevent spread of the disease to its healthy neighbors. Infected plant tissue can also be removed from the garden at the end of the growing season to reduce the pathogens ability to survive from one season to the next.

Infected plant parts can be composted if the compost pile heats up to 160F. Otherwise infected plant parts can be buried, burned or disposed of in the trash. Follow local city or county regulations regarding disposal of plant material. Many cities offer municipal composting sites for yard materials.

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Photo 2: Moisture favors growth of fungal and bacterial pathogens.  M. Grabowski UMN Extension.
Manage Moisture - Most fungal and bacterial plant pathogens thrive in moist environments. Moisture on the surface of leaves and stems allows these pathogens to infect, grow, reproduce and spread. Roots growing in heavy wet soils are prone to root rot. Create an environment that favors plant growth, not disease development, through proper water management.

Use drip irrigation or a soaker hose to water plants. This puts water in the soil, where roots can take it up, not on the leaves, where fungi and bacteria thrive. If using sprinkler irrigation, water early in the morning so leaves dry quickly in the sun. Avoid watering as the sun goes down. Wet leaves will remain wet for many hours in the night, providing excellent growing conditions for fungal and bacterial plant pathogens.

Water deeply and infrequently. This will encourage growth of deep plant roots and will allow soil to dry slightly between watering. Continuously wet soil favors the growth of some root rotting pathogens and can suffocate roots. Amend heavy soils with organic matter to improve soil drainage.

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Photo 3: Soaker hose in the flower garden. M. Grabowski UMN Extension.
Mulch the soil with an organic mulch like wood chips or straw. This will keep moisture in the soil and reduce humidity in the plant canopy. Mulch also helps to reduce the spread of plant pathogens that splash from leaf debris in the soil onto the lower leaves of plants.

Space plants to allow good air movement through the garden. This will help leaves dry out quickly after rain and irrigation.

Tolerate a Non-threatening Disease - Remember not all plant diseases are deadly. In fact many common diseases in the yard and garden affect the aesthetics of the plant more than the health of the plant. Learn more about the plant disease you have encountered at before deciding what level of disease control is necessary. Some diseases like oak wilt or Dutch elm disease require action. Others, like powdery mildew on lilac can be tolerated as they will cause no significant damage to the plant.

Little Worms Under Elm

Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist

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Photo 1: Elm gall midge larvae on sidewalk. Unknown.
Large numbers of very small, about 1/16th inch long, pinkish worms were found during mid April under elm trees. Looking like grains of rice, these 'worms' are actually a type of fly known as a gall midge. It is not clear what species is present but they appear to attack the developing samaras (winged seeds) in early spring. Later in the spring (sometime in April to early May), the mature larvae drop to the ground where they remain until the next spring. The galls are harmless to the tree and no control is necessary. The larvae can be a nuisance when they fall on driveways or sidewalks. The only necessary step is sweep them off. This is a short lived problem that will go away on their own.

Be on the Watch for Ticks

Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist

With the early spring we have been experiencing this year, ticks have also been active sooner than normal. The two most common ticks we encounter are the American dog tick (also known as wood tick) and the blacklegged tick (formerly called deer tick). Both of these ticks are found in the underbrush of hardwood forests and adjacent open grassy fields

Both are annoyances because they bite people and our pets as they seek blood meals. However, blacklegged ticks are particularly a pest because of their ability to vector diseases. The most common disease they can transmit in Minnesota is Lyme disease (1,050 cases in 2008). Lyme disease is most common in central and eastern Minnesota. Blacklegged ticks are also known to vector human anaplasmosis (278 cases in 2008), babesiosis (24 cases in 2007), and Powassan virus (2 cases ever reported, both in Cass county).

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Photo 1: Blacklegged tick close-up. Jeff Hahn.

There are certain conditions that must occur for a blacklegged tick to successfully transmit a disease to you. First, it must be attached and biting you; if it is just crawling on you, it can not transmit disease to you. Second, if it is attached to you, it must be biting long enough. For Lyme disease, the blacklegged tick must be biting for at least 24 - 48 hours; for human anaplasmosis it needs to be biting for 12 - 24 hours. So if you go out into the woods in the morning and find a blacklegged tick biting you in the afternoon, it is doubtful that it has been attached long enough to transmit Lyme disease or human anaplasmosis.

Up to 30 days after contracting Lyme disease, most people (70 - 80%) experience a red circular rash. They may also experience fever, chills, headache, muscle and joint pain, and fatigue. If left untreated, these symptoms can progress into additional rashes, fever, arthritis, muscle pains, irregular heartbeats, stiff neck, and persistent fatigue. If Lyme disease continues to progress, symptoms that may be experienced weeks or months after the onset of illness can include swelling in joints, like knees, continued persistent fatigue, and nervous system problems.

If you suspect you may have contracted Lyme disease or another tick-borne disease, see your doctor. For information on other tick-borne diseases, go to Tick-borne Diseases in Minnesota.

Prevention is the best method to avoid ticks. Stay on trails when possible. Wear protective clothes, such as long pants and long sleeve shirts (tuck pants into socks for additional protection). Use repellents to maximize your protection. Apply DEET on clothes or skin. Use permethrin just on clothes. Permethrin is effective for several wearings and will be effective even if clothing is washed. It is not necessary to saturate clothing or skin with repellent, just apply enough to covered the desired.

When returning from a known tick area, be sure to check yourself for ticks. Promptly remove any and save for identification. For more information on ticks, see Ticks and Their Control.

Spring Insects Are Early

Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist


Photo 1: Recently hatched forest tent caterpillar.Jeff Hahn.

We are experiencing a noticeably early spring. Consequently this has caused insects to become active earlier than normal. During April, insects such as forest tent caterpillar, European pine sawfly, and pine spittlebug were already active, about 3 - 4 weeks ahead of schedule. Undoubtedly, many garden insects are also active as well. That is not to say all of individuals of a species have become active, but at certain sites they have.

If you are anticipating a particular insect problem for mid May, look now, it probably is already present. If you are looking for an insect that normally comes out in early May, it probably is already is active. Inspect your garden and landscape now for potential insect pests.

Thursday, April 1, 2010

What Should I Do With My Ash This Year?

Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist

Thumbnail image for DSC_0440.JPG
Declining due to EAB
Jeffrey Hahn
With the discovery of emerald ash borer (EAB) in Minnesota last year, people with ash on their property are concerned about possible attacks from EAB and what they should do, if anything, to protect their trees. Insecticides are an effective method to protect your ash from EAB but does this mean this is what you should do? There are a number of factors that people should consider when weighing their options.

The first factor you should consider is how far are you from a known EAB infestation. The general guideline is that the highest risk from EAB occurs when you are within 10 -15 miles from a known infestation. Right now, EAB is only confirmed in St. Paul and Minneapolis. This means that essentially all of the Twin Cites metropolitan area is at a high risk. However, if you are in Minnesota outside of this 10 - 15 mile radius, the risk from this exotic borer, while not zero, is much smaller and treating your ash for EAB is not suggested.

You should also ask yourself what condition is your ash in. When trees are healthy or at least mostly healthy, i.e. dieback or decline in the canopy does not exceed 40% - 50%, they are a possible candidate for treatment. If the trees are in poor health and the canopy shows over 50% dieback or decline, it's not worth saving the tree. Also, when a tree has suffered significant girdling damage from borers, its ability to move insecticide through the tree to protect it is greatly reduced.

How valuable is your ash to you? Does it provide shade for your house; is it an important part of the aesthetics of your yard; does it has sentimental value? Or is it just another tree in your yard and it wouldn't be missed? The more valuable your ash is, the more likely you will try to save it.

You should balance these factors with the cost of treating trees versus the cost of removing and/or replacing trees. When considering insecticides, remember that the cost will vary according to how large the tree is, how many trees you are treating, what insecticide is being used, and the fees charged by individual companies.

It is very important to remember that once you start using insecticides, it is a long term commitment and you need to continue to treat your ash regularly (every 1 - 2 years) for the life of the tree. Ash do not develop any resistance when they are treated, so if you stop using insecticides after a number of years, they are just as vulnerable to EAB as they were before you started to treat them. So while the cost of a removing a large ash may be considered to be expensive by some, it is a one time cost compared to the ongoing, long term price of treating trees.

What is the right action for you to take? There isn't one right answer. What a person may do will depend on their particular circumstances - the right solution for one property owner may not be appropriate for someone else. However, consider the above factors to help you make a decision that is right for you.

Planting Bare-Root Woody Plants

Kathy Zuzek, University of Minnesota Extension Educator

Spring is here bringing planting season. Early spring between the time that the ground thaws but before bud break is one of two optimal times during the year for planting bare-root trees and shrubs.

What is a bare-root plant?

A bare-root tree dug from a nursery
Gary Johnson

The name says it all. Bare-root nursery stock are trees and shrubs that are field grown for one to three years, undercut and dug in fall and spring, handled with no soil left around roots (Photo 1), and stored with moist roots and dormant tops at a temperature a few degrees above freezing until they are planted. If you have never seen undercutting in action check out this You Tube video:

Advantages and Disadvantages of Bare-Root Plants

Bare-root stock offer several advantages:
  • Bare-root plants are usually ½ to 2/3 of the cost of containerized or balled & burlapped plants because bare-root plants are easier to handle, store, and ship.
  • Longer root lengths are possible on bare-root plants since weight of the soilless root ball is minimal.
  • The entire root system of a bare-root plant can be inspected so deformed, circling, and broken roots can be detected and corrected or removed.
  • Appropriate planting depth is easy to gauge because the root system is visible.
  • Because there is no soil around the root zone, there is none of the dramatic change in soil interface between the rootball and native soil that can hinder plant establishment.

There are also disadvantages to planting bare-root trees and shrubs:

  • The range of plant sizes and plant types in bare-root plants is smaller. Bare-root trees are usually a 2" caliper or less, because larger sizes do not transplant well as bare-root plants. Caliper is the diameter of a tree stem, measured 6" above the ground. If that stem diameter at 6" above the ground is greater than 4", move up the stem another 6" and measure the diameter at 12" above the ground for your caliper measurement. Evergreens are not sold as bare-root plants unless they are very small seedlings.
  • Bare-root plants should be dormant when planted so there are seasonal restraints to planting. 
  • Early spring between the time that the ground thaws but before bud break is one time to plant bare-root plants. Autumn is a second good time to plant bare-root stock. Soil temperatures and moisture levels encourage active root growth at these times of year and lower air temperatures and dormant crowns help to minimize transplant shock. 
  • Careful handling of bare-root stock is important. The exposed root system cannot be allowed to dry out during handling, transporting, or planting.

How to Plant Bare-Root Woody Plants

Diagram: Planting a bare-root tree. SULIS

Never allow the roots of your bare-root plant to dry out between purchase and planting. Keep the roots moist and protected from wind and sun. If you can't plant immediately, place the plant in a cool, shaded, sheltered location and cover the roots with moist straw, hay, damp burlap, or loose moist soil.

Bare-root plants lose up to 95% of their roots when they are undercut and removed from a nursery. After transplanting it is hard for this reduced root system to absorb enough water to meet the needs of the plant. Until the root system grows and reestablishes to its normal size, a newly planted tree or shrub often experiences transplant shock, which is primarily drought stress. You should plant and care for your bare-root plant in a way that provides the optimal environment for root growth and replacement during the first few years after transplanting.

Optimal planting and care include:

  • A planting hole only as deep as your root system's height. This prevents settling and all of the stresses caused by deep planting.
  • A planting hole at least 2-3 times as wide as the root ball that allows for rapid root growth through the backfill soil before hitting growth-slowing compacted soil outside of the hole.
  • A planting hole with sides that slope towards the base of the hole. The majority of a woody plant's roots grow in the top foot of soil and a planting hole with sloping sides encourages new roots to grow horizontally and towards surface soils.
  • A planting hole backfilled with the original soil. Adding amendments to improve soil quality doesn't help and sometimes hurts by causing poor water drainage in the planting hole. Your time is better spent digging a wider planting hole than amending soil.
  • Adequate watering until the plant replaces missing roots. Water is usually the most limiting factor affecting plant growth after transplanting. Because your bare-root plant has lost the majority of its root system, it relies heavily on water in the root ball through the first growing season. For a bare-root tree with a caliper of 2" or less that is planted on a well-drained site, apply 1 to 1 1/2 gallons of water per inch of stem caliper daily during the first week after planting, then every other day for 1-2 months , and weekly after that until the plant is established.

Establishment Tips for Bare-Root Woody Plants

How long does it take for a bare-root tree to become reestablished? That depends on genetics, environmental factors, and tree size. A good rule of thumb for Minnesota though is to assume that it will take 1 ½ years of time for each inch of stem caliper. So a 1" caliper tree will replaces its roots in 1 ½ years while a 2" caliper tree will take 3 years.
  • A 3" layer of organic mulch instead of turf under the canopy of your tree or shrub. Organic mulch eliminates the competition for water and nutrients that sets up between roots of grass and woody plants, suppresses weeds, retains soil moisture, buffers soil temperatures, protects stems from mechanical injury, and adds organic matter to the soil. Make sure that your mulch is pulled back a few inches from stems to eliminate direct contact.
  • No pruning except to eliminate problems and to ensure good branch structure. Remove diseased, dead, broken, crowded, and crossing or rubbing branches or to encourage a central leader, to eliminate narrow branch crotches with included bark, or to remove basal sprouts on trees. Leaving as much of the crown intact as possible maximizes photosynthate production that can be used to promote root and trunk diameter growth.
  • No quick-release nitrogen fertilizers in the planting hole. Direct contact between quick-release fertilizer and roots will burn the roots. Slow-release and organic fertilizers can be incorporated into the backfill soil. See the trees, shrubs, and fruits section of for more information.
  • Staking if your new tree is densely-crowned and planted on sites with lots of wind exposure. Attach stakes with flexible web belting or any other strips of wide, soft, but strong materials low on the tree trunk. This will prevent movement of the lower trunk and the root system, but allow for movement and resulting strengthening in the top of the tree. Staking may be necessary for 1-3 years while roots are growing and beginning to stabilize the tree. Check the attachment points of the webbing or strips on the stem every 3 to 6 months and loosen if necessary. For more information see: We are sorry, this link is no longer available.
  • Trunk protection for smooth-barked species such as crabapples, lindens, and maple will prevent injury from sunscald. Apply paper tree wraps or white wraps made from synthetic material from the bottom up in an overlapping pattern until the first major branch is reached. The wrap can be secured with duct tape or expandable plastic tape. Apply tree wraps in late October or early November and remove in March or early April.

Lawn Grass Varieties, Seed Labels, and What to Plant Where

Bob Mugaas, University of Minnesota Extension Educator

This is the third and final article in a series of articles related to choosing and selecting the best MN adapted lawn grasses for this area. This last topic will address the topics of what to do when you can't locate the particular grass varieties you've identified, how to read a grass seed label to know what you're really buying and some suggestions for the kind of grass seed mixes to use in various locations around our home landscapes. The previous posts are listed here:

Series: Choosing and selecting the best MN adapted lawn grasses

Tips for selecting the best available grass seed varieties

Kentucky bluegrass seed sold in bulk
Karen Jeannette

Selecting and then finding specific varieties of grass seed is not always as easy as you might think. Unlike the relative ease of finding your favorite tomato or marigold varieties through seed catalogs or the internet, looking for specific grass varieties can be much more challenging. It can be quite frustrating to go to a local garden center expecting to find at least some of your particular grass varieties but not see one of them listed on any of the grass seed labels carried by that retail outlet. Instead there are varieties listed that are completely unfamiliar to you. So, what's a person to do?

First, it's important to remember that not all varieties from a seed grower/supplier available in the marketplace will have gone through one of the state and/or national evaluation programs mentioned in last month's article. Indeed, seed growers and some supply companies will have also conducted their own independent variety research. From that research, they will make determinations about what varieties would be suitable for use in mixes to be packaged and sold in the retail or wholesale market.

Second, availability of particular varieties can also be a function of supply and demand characteristics. In some cases, the demand for a particular variety or varieties for use in larger wholesale markets (as well as for sod production) can exceed the supply of those varieties leaving little or none left to be packaged into the homeowner available quantities. In other instances, the availability of seed from particular varieties may be quite low for that year due to a number of possible causes (e.g., poor seed production, adverse weather conditions, etc.) Once again, those particular varieties may not show up either in commercial wholesale mixes or in the seed mixes available at local garden centers or retail outlets.

Finding recommended grass varieties, or the next best thing

So, that still leaves us with the question of "What's a person to do when they can't find the particular varieties they've identified?" One thing that can be done is to jot down the names of the varieties that are listed and go back to the resources mentioned in last month's blog and see if you can find anything about those particular varieties. As with many other things that we purchase, cheaper prices can mean lesser quality. The same would also be true for purchasing grass seed. In general, high quality, 'clean' seed will generally cost more but will almost always provide better results. Staying with reputable, highly regarded name brands of grass seed is usually a good first step even though the specific varieties you were looking for don't seem to be contained in the packages. In other words, the suppliers will most likely still try to provide good quality cultivars that will in turn help the end user, you and me, to achieve good results with their seed mixes. It's also important to remember that seed cost is usually going to be the least expensive item relative to the work and preparation needed to ensure the conditions necessary for successful seeding. Buying cheap, poor quality seed, can jeopardize a project's success no matter how careful all of the preparation work might have been done.

Interpreting the grass seed label

The next logical question one might be asking is "How can I tell if I'm getting both good value and quality in a seed mixture?" That question can best be addressed by examining the different parts of a grass seed label for information that can shed some light on grass seed quality.

Determining what is high quality seed need not be that difficult. Purchasing high quality seed can be easier if you understand a few basic terms on the grass seed label. Figure 1 is a fictitious grass seed label that will be used to discuss the various components of a label. All labels must provide information about the grass seed purity, its germination potential, crop seeds present, weed seeds present, noxious weeds present, and inert components in the package.
Much of the grass seed available in Minnesota comes from the west coast states where climates are most favorable for seed production. However, the very northern reaches of Minnesota are also home to a number of large, well established grass seed production farms. Seed from that area is also available through various outlets in Minnesota. Below Figure 1 is a list of terms you will find on grass seed labels and what they mean.

Terms Found on Grass Seed Labels

  • Lot number. This identifies the larger seed lot from which this particular seed came from. If there are issues related to the purity or growth of this mix, the lot number can be very important in tracing back to where problems might have originated.
  • Test date (month/year) It is always important to buy 'fresh' seed, that is, seed that has been tested within the year when it is purchased. This information tells when the seed was tested and determined to have the characteristics described further on in the label. It is also a useful date when one is trying to determine how long a particular bag or box of grass seed might have been stored and whether it will still grow or not. In general, it is usually better to buy new, fresh seed if more than two or three years old. This will be especially true if the seed has been stored anywhere else other than in cool to cold, dry storage. In most cases storage in garages or basements will not provide the necessary storage conditions to retain good seed viability. Again, in the bigger scheme of things and relative to the seeding preparation investment, the purchase of fresh, good quality seed is likely to be the least expensive part of the project. Bottom line: Always purchase and use fresh seed!
  • Variety These will be the names (when possible) of the actual turfgrass varieties contained in the mixture. In some instances, you will notice a generic term for a species of grass but no specific variety listed. For example, you might see the term 'creeping red fescue, VNS'. The VNS indicates 'variety not stated'. In other words, you know that you are getting a percentage of creeping red fescue but not which specific variety it may be. One shouldn't necessarily consider the term VNS to mean that the grass contained in the mix is a bad grass variety. There could be a number of valid reasons for not being able to list a particular variety. In most cases though, good quality seed mixes will usually try to list specific varieties whenever possible. 
  • Purity (Pure seed) is the percent by weight of pure seed, crop, weed, and inert ingredients in the package. These percentages added together should total 100 percent. Purity is concerned only with quantity, not quality. That is, not all seeds present in the package are capable of growing. To determine the seed that will actually grow or what is known as pure live seed, the percentage purity should be multiplied by the germination percentage. In this example, 31 percent by weight is Kentucky bluegrass (purity). The germination percentage for that variety of Kentucky bluegrass is 80. If one multiplies the purity value times the germination value you will determine how much of the seed will likely grow (under favorable conditions). When carrying out this calculation you will come up with a value of 24.8%. In other words, of the 31% Kentucky bluegrass contained in the mix, 24.8% of it actually has the capacity to germinate and grow. It should be apparent that you should always seek to purchase the highest purity of grass seed compared to the other contents and the highest germination percentages as possible.
  • Germination is the percent of pure seed that will germinate and grow in an ideal laboratory environment during a prescribed length of time. Since field conditions rarely duplicate these laboratory conditions, it is especially important to purchase seed with the highest germination percentage possible. As noted above, this is the percentage used to determine pure live seed.
  • Crop is the percent by weight of seeds normally considered to be grown as an agricultural crop such as grain. This can include other types of grasses that may be undesirable in a lawn. This percentage should be as close to zero as possible.
  • Weeds refer to the percent by weight of all seeds in the package that are not otherwise listed in pure seed or crop. It is not required to identify these weeds or how many there are since this is on a percent by weight basis. For example, one or two large seeds of a weed would pose no particular threat to the new lawn. However, even a small percent by weight of very small seed could account for thousands of weed seeds distributed over the area. This percentage should always be as low as possible.
  • Noxious weeds are listed as the number per pound, not the percentage per pound. Noxious weeds are weedy plants considered by individual states to be very difficult to control and that could pose hazards to both humans and livestock. While this is often more of a problem in farm crop seed, one should always purchase grass seed without the contamination of any noxious weeds.
  • Inert is the percent of material contained in the package that will not grow under any condition. Broken and damaged seeds, chaff, and empty seed hulls are just some of the more common inert material included. Obviously, this percentage should be as low as possible.

First Things First: Right Grass Seed - Right Place - Right Function

Side-by-side comparison of Kentucky
bluegrass and fine fescue grass species
Bob Mugaas
The final information in this article is intended to provide some help in choosing a particular mix of grass seed for particular areas and uses in our yards.
  • Avoid the temptation of a one-seed-mix-fits-all approach to purchasing grass seed for your property.
  • Pay special attention to site differences that may require a different mixture of seed to perform well. The most obvious of these conditions is for one area to be shady while the other part of the yard is in full sun.
  • It may be necessary to choose multiple grass seed mixes for the same residential site in order to have the best adapted grasses planted in the different site conditions. Below is a guide to a number of possible grass seed mixes to fit various needs.
  • Choosing the right plant for the desired location is of utmost importance for long-term plant health.
  • Match the intended use of the lawn area with the proper types of grasses when choosing turfgrass varieties, blends or mixes. See below for site examples to help you match appropriate turfgrasses with the intended site and function.

Site Examples: Matching lawn site and function to seed varieties

Full-to-partly sunny conditions with minimal traffic or wear, low-to-moderate inputs intended.
  • 60% to 70% Kentucky bluegrasses, 20% to 30% fine fescues, ~10% perennial ryegrass.
Site 2:
Full-to-partly sunny conditions with moderate-to-high levels of traffic and/or wear, moderate-to-high inputs required for rapid recovery:
  • 75% to 85% Kentucky bluegrass, ~15% to 20% perennial ryegrass.lawn for partshade.jpg

Photo 3: Area well suited to Kentucky bluegrass fine fescue combinations such as those for site examples #1 or #3.Karen Jeannette.
Site 3: Shaded for a portion of the day or receives partial shade all day with minimal traffic or wear, primarily a dry shade:
  • 65% to 75% fine fescue; 25% to 35% Kentucky bluegrass (shade tolerant cultivars); ~10% perennial ryegrass.
Site 4: Shaded for a portion of the day or receives partial shade all day with minimal traffic or wear; a somewhat moist shade:
  • <30% to 40% fine fescue; 25% to 35% Poa trivialis, 20% - 30% Kentucky bluegrass (shade tolerant cultivars) ~10% - 15% perennial ryegrass.
Site 5: Full sun-to-very light shade, little to no inputs intended
  • 70% to 85% fine fescues; 10 - 20 % common Kentucky bluegrass; 5 to 10% perennial ryegrass.
Notes about using Ryegrass (Lolium perenne) and Roughstalk bluegrass (Poa trivialis) species in grass seed mixes:
  • Be a little cautious when adding perennial ryegrass to a mix. Research has shown that a 50/50 mix of Kentucky bluegrass to perennial ryegrass results in a stand that may be dominated by perennial ryegrass even though there are many more seeds of bluegrass than perennial ryegrass in the mix.

  • Because of the seedling vigor of annual ryegrass, it is sometimes used in general-purpose seed mixes; but almost never in mixes for "elite" or "premium" turf.

  • Note that the bluegrass species, Poa trivialis, sometimes referred to as roughstalk bluegrass, is better adapted to shadier more moist conditions and usually becomes the dominant species over time in that environment. However, because of the potential aggressiveness of Poa trivialis under favorable growing conditions, some people prefer to avoid using it even though it is well adapted to those conditions.

Hopefully, this article along with the other two previously published articles, Know Your Minnesota Lawn Grasses ( and So what are the best grass varieties? (, you'll get a good start on selecting and purchasing the best adapted, highest quality grass seed for your particular situations.

Hackberry Witches' Broom

Michelle Grabowski, University of Minnesota Extension Educator and Jeff Hahn, University of Minnesota Asst. Extension Entomologist

hackberry witches broom 11.jpg
Hackberry tree with witches brooms
W. Cranshaw,
As you look up at the trees this spring, watching for emerging buds or perhaps a returning song bird, you might notice many small clumps of short twigs scattered through the branches of some hackberry trees (Celtis occidentalis). These clumps of twigs are called witches' brooms.

Although witches' brooms are present within the trees canopy throughout the year, they are most easily observed in the winter or early spring, before leaves emerge. Hackberry trees growing in open areas, like a yard or along a street, are more likely to have witches' brooms than hackberry trees in a forest. Often one hackberry tree will have many witches' brooms while its near neighbors have none.

Witches' brooms occur when the bud of the tree is injured or infected. Normally, a healthy bud opens to produce one shoot. However, when a bud is damaged or killed, multiple weak shoots may develop from the same point on the branch. Witches' brooms in trees can be caused by a variety of problems. Trees growing alongside roads where salt is applied in the winter may have buds damaged or killed by splashing salt. In some cases, infection of the tree by a fungus, a phytoplasma or even a parasitic plant like mistletoe can cause witches' brooms to form within the tree's canopy.

hackberry witches broom 1 .jpg
Witches broom on hackberry tree, up close
W. Cranshaw,
The exact cause of hackberry witches' broom remains unknown, although two organisms are consistently found within these twig clusters. The first is an eriophyid mite, Eriophyes celtis. Eriophyid mites are tiny, measuring no more than 0.5 mm (1/50th inch) long. Even with magnification, people are unlikely to see these mites. Little is known about their life cycle. We do know that eggs are laid in May and mites cluster on the buds, developing until the end of the summer. The second organism is the powdery mildew fungus Podosphaera phytoptophila. The fungus may be seen as a white cobweb like coating growing on the young shoots and leaves within the witches' broom in spring or early summer. Throughout the year tiny brown to black round fungal resting structures can be found on infected buds, but these are best observed with the help of a magnifying glass.

How these two pests interact with the hackberry tree is uncertain. One theory suggests that the eriophyid mite causes the witches' broom to form and the powdery mildew fungus takes advantage of the weakened plant and starts an infection secondarily. It is clear that hackberry witches' broom causes little damage to the health of the tree. Trees with numerous witches' brooms have been found to grow vigorously for years.

hackberry witches broom .jpg
Several hackberry witches brooms, up close
Jeff Hahn
Since the true cause of the witches' broom remains uncertain, there is no known method to prevent or to control the problem. Gardeners who are concerned about the affect of the witches' brooms on the ornamental value of the tree can prune off severely infected branches. In most cases however, hackberry witches' broom is only an aesthetic problem in the winter months. The flush of new leaves soon to be produced will hide the witches' brooms, leaving only a beautiful green canopy to be seen by the casual observer.

Repairing Spring Flooded Lawns

Bob Mugaas, University of Minnesota Extension Educator

Early spring, before lawns are actively growing (i.e., foliage is still mostly brown) lawn grasses can withstand several days of being submerged without suffering serious damage. If floodwaters are cold (<60 degrees F.), as they usually are in early spring, lawn grasses can withstand being submerged for even longer periods of time.

Moving water is usually less harmful to lawn grasses than is ponded, stagnant water. Ponding occurs in areas of poor drainage or results from water being left behind in valleys and depressions when floodwaters recede. Spring flooded lawn areas where the water has risen and then receded rapidly often escape serious permanent injury and death.

Post flooding lawn care

Once the soil has dried sufficiently such that it is no longer soggy and slushy underfoot, pick-up and remove debris such as wood, glass, stones, sheet metal, paper products along with other forms of junk deposited by flood waters. It is even good to remove thick layers of leaves or other debris that can smother the grass. Debris can be a safety hazard so exercise caution when picking up and handling this material. Debris left behind can later become a hazard to people operating lawn equipment as well as damaging the equipment itself. It should be noted that the drying process may take two or three weeks, perhaps longer, depending on site conditions.

Assessment of potential lawn damage and recovery may not be possible until those areas have dried. Checking for new shoots emerging from the soil or the emergence of new shoots from surviving plants is a good way to make an early assessment of damage. Usually, once regrowth has begun, it will continue although it may take several weeks before the lawn has completely filled in and begun to thicken up.

Often a more significant effect of flooding is the deposit of sediment, primarily silt, over lawn surfaces. This can lead to serious soil layering problems and even death of existing grass.

Lawn repair solutions for floodwater soil deposits less than 1 inch

Core aerification can be one of the most important and beneficial operations conducted where silt deposits are less than an inch and water has not ponded long enough to cause substantial death of the lawn. When the lawn has begun to actively grow as evidenced by new green grass blades appearing, go over the lawn about 3 times with a core type aerifier. This will help improve overall soil structure, improve soil oxygen levels, help break up soil layering problems caused by the overlay of silt and encourage recovery during the remainder of the growing season. A second round of aerification in early September will be helpful in further promoting active turfgrass growth and recovery through the fall period.

Overseeding can also be done at the time of aerification. Be sure that good seed to soil contact is achieved. To prepare a smooth seed bed, break up the aerification cores with a lawn rake or power rake (i.e. vertical mower). If desired, lawn seeding can be delayed until mid-August through early-September. Sodding can be done successfully throughout the growing season.

Lawn repair solutions for floodwater soil deposits more than 1 inch

Soil deposits in excess of an inch and just barely covering the turfgrass plants should be carefully scraped or washed from the lawn surface prior to any reestablishment. This will also help remove any floodwater pollutants left behind that may have a more lasting detrimental effect on the lawn since their concentrations are completely unknown.

If the lawn area is completely buried with inches of silt, then the best renovation strategy may be to accept that the majority of the lawn has already been severely damaged or killed and it will be necessary to reestablish a "new" lawn. Even though the process of silt removal is a lot of work and can be very damaging to existing turfgrass plants, reestablishing a lawn should begin by removing the excess silt as completely as possible. This should be followed by good soil preparation practices whether the lawn is to be seeded or sodded. See Extension factsheet 5775 Seeding and Sodding Home Lawns ( for more information on seeding or sodding a new lawn.

Where soil removal is not possible, rototill or plow the area thoroughly mixing the soil deposits from the floodwater with the existing soil and dead turfgrass cover. This will help restore more uniform soil conditions creating a better environment for grass to reestablish. One of the main goals of this operation is to help break up soil layering problems that can be caused by the silt deposits as well as the old sod layer. Seeding or sodding can be done as described in the above mentioned publication.

Introduction of new lawn weeds

Another problem that may be encountered with silt deposits is the introduction of potentially new and different weeds to the lawn. Therefore, it may be necessary to use pre- and/or post-emergence herbicides where appropriate during the reestablishment process. Make sure to follow labeled recommendations when using any herbicide to avoid injury to the young grass plants.

Extension resources for lawn repair

While dealing with the lawn may be the very least of one's water problems this spring, those needing to repair their lawn can do so once the soil has sufficiently dried. Local County Extension offices should have the publication FO-3914 entitled Lawn Renovation for additional information on repairing lawns. (The online link is:

Rove Beetles

Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist

An interesting sample was received from northwest Minnesota in March during a week when the weather was unseasonably warm. More than 20 insects were found on the carpeting in a couple of rooms in a Senior citizens' home. They were worried that they would be damaging and spread to other areas of the building.

rove beetle howard person.jpg
Rove beetles
Howard Person
The insects in question are a species of rove beetle. Rove beetles are very common insects, although the are often overlooked by people. Most are small, 1/16th - 1/8th long and are conspicuous because of the short wing covers they possess which leaves much of the abdomen exposed. Rove beetles are often associated with dead animals and dung as well as on the ground under stones and other debris. They are predaceous on other insects.

Fortunately, rove beetles are not harmful to people or our property. They do not reproduce indoors and are just a temporary nuisance. It is likely that these particular beetles overwintered near the building and wandered indoors when warm temperatures arrived. The use of a vacuum or some other type of physical removal is the only necessary control.

Arboretum Challenge: Veggies by the Yard

Leslie Cooney, Membership Services Manager, Minnesota Landscape Arboretum
Are you thinking about your gardens? Starting seeds? Planning a vegetable bed? Need a garden plan?

The Arboretum is issuing a challenge to all gardeners out there to plant and compare with something we're calling "Veggies by the Yard." Part of our summer exhibition on Powerhouse Plants, we're going to find out just how much food can be grown on a 4x12 ft. plot. Our website offers several vegetable garden plans to choose from:

We'll keep a harvest tally of our yields and ask you to do the same - entering the data online every Saturday June through September. It's a chance to go head to head with Ted Pew, our valiant veteran veggie guy and landscape gardener extraordinaire!
Photo: Will you be planting one of the Veggies by the Yard garden plans this year? Karen Jeannette.
Find out more about how you can participate in the Minnesota Landscape Arboretum's Veggies by the Yard by visiting:

April 2010 Garden Calendar

Contributors: Karen Jeannette, Research Fellow and Yard and Garden News Editor; excerpts from the 2010 Minnesota Gardening Calendar.

Plant tips

soil sample.jpg
Soil sample from a shade garden area
Karen Jeannette

Prepare Your Soil

  • Find tips for fertilizing, composting, maintaining soil health, and plants for tough sites here.


Need ideas for the vegetable or edible garden?
  • Use the pre-designed veggie garden plans and participate in the MN Landscape Arboretum challenge: Veggies by the Yard.


  • Fertilize your lawn to keep it growing vigorously enough to help keep weeds out. Wait until you've had to mow it once or twice though, so you know the roots are growing actively and can make good use of the added nutrients. Seep up and reuse any granules that land on hard surfaces such as sidewalk or driveways, then water the fertilizer lightly into the soils so it "catches" and won't easily wash into storm drains when it rains.
  • If you've seen crabgrass appear early in warmer parts of your landscapes (by sidewalks, driveways, or south-facing slopes) in the past, apply a pre-emergence herbicide towards the end of April in the Twin Cities areas, a week or more later farther north. Otherwise, wait until early to mid-May to spread crabgrass preventer. Whether using a traditional product or corn gluten meal, you must water the lawn lightly afterwards to activate the herbicides ability to stop weed seeds as they sprout.

Trees, Shrubs, Flowers

Mulch used for winter protection can be
removed gradually as soil and mulch thaw
Karen Jeannette
  • Begin to remove protective cover from bulb beds, non-hardy roses and perennials in stages as soil and mulch thaw. Don't rush to uncover tender plants, though. Mulch helps prevent them from coming out of dormancy too early, when damaging cold is still a possibility. Rose canes will be okay as long as temperatures hover around twenty degrees, but most flowering perennials will die back when it's that cold.
  • Prune shrubs grown for their foliage rather than flowers, as soon as their buds swell. (Early pruning removes flower buds.) Many shrubs - dogwood, alpine currant, burning bush, and others produce tiny flowers, but they're not showy enough to worry about eliminating them. Wait to prune junipers, yews, and other evergreens until you see this year's new growth expanding. Prune forsythias, azaleas, lilacs, and other flowering shrubs only after they're finished blooming. For more about pruning flowering shrubs to maximize bloom, click here.
  • Don't prune or take care to avoid wounding oaks from April through October. April begins the period of high risk Oak Wilt susceptibility. If trees are accidentally wounded or pruning is unavoidable, cover the wounds immediately-within minutes-with one of the preferred materials such as water-based paint or shellac. For more information on Oak Wilt, click here
  • When is it safe to plant perennials and annuals? Wait until mid-to late May to plant perennials and until after your area is frost free before planting flowering most annuals.  See the MN spring frost-free map to identify when your area is likely to be frost-free. 


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