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Extension > Yard and Garden News > April 2015

Thursday, April 30, 2015

Watch out for ticks!

Jeffrey Hahn, Extension Entomologist

Spring is finally here.  And it once again is tick season.  Be aware of these blood thirsty arachnids when you are in fields, wooded areas, and other areas where ticks are know to frequent.  There are two common ticks in Minnesota, the blacklegged tick (also called deer tick) and the American dog tick (also called wood tick).

Both are nuisances because they bite to take a blood meal from not only people but also pests including dogs and horses. Blacklegged (deer) ticks are also a particular issue because they are a potential vector of Lyme disease and other diseases (see also Tick-borne disease in Minnesota). 

Protect yourself when you are out in known tick areas:
  • Stay on trails and try to stay out of brushy, grassy areas where ticks are more common.  
  • Wear long, light colored pants; for additional protection, tuck your pants into your socks.  
  • Use repellants: Deet can be treated on clothes and skin while products with permethrin can only be applied to clothing
  • Do a tick check when you return from the outdoors.  They are small and can be easily overlooked so look carefully.  Be sure to look in out of the way places, like behind ears or behind knees.

Adult female blacklegged (deer) tick. a potential vector of
Lyme disease and diseases. Photo: Jeff Hahn, UMExtension
If you do find a tick, especially if it has been biting, get it positively identified.  While American dog ticks are not an important disease vector, blacklegged (deer) ticks can transmit an array of diseases, especially Lyme disease.  For more information, see Ticks and their control.

Wednesday, April 29, 2015

Ignore Andrenid Bees

Jeffrey Hahn, Extension Entomologist

Andrenid bees are a type of native ground-nesting bee that is first seen during early spring. Residents are discovering them now in their gardens and lawns.  Some people have been concerned that these insects may be ground dwelling yellowjackets (wasps) but the overwintering queens are only just starting to build new nests and people would not be seeing any activity from their nests this early.

Andrenid bees like to nest in sunny, dry areas of gardens
and yards. Photo: Jeff Hahn, UMExtension
Unlike honey bees and bumble bees which are social insects, andrenid bees are solitary so there is only one bee in a nest. But they are gregarious which means that there are many nests in a small area. They prefer to construct their nests in loose soils, like sandy or sandy loam soils. It is common to find andrenid bee nests on dry sunny slopes or small hills. The nests are somewhat mounded up and can resemble ant nests.

Andrenid bees are important pollinators. Tolerate them
whenever possible. Photo: Jeff Hahn, UMExtension
An andrenid bee is about ½ inch long with a black abdomen (sometime it has bands of hair giving it a striped appearance) and has whitish or yellowish hairs on its thorax (the segment behind the head). They are very gentle, docile insects and are extremely unlikely to sting even when there is activity around their nests. Since they are the only bee in their nest, they do not defend it like social bees and wasps would; they need to avoid being injured or killed so they can maintain their nests and care for their young.

These native bees are very important pollinators and should be tolerated. They are active for several weeks, and then complete their life cycle. They are gone on their own by May so they are only present during spring.

Check Junipers for Disease Damage

M. Grabowski, UMN Extension

Junipers may be tall, upright, and stately, or low creeping shrubs, but regardless of form, many junipers sport dead tips and brown needles in early spring. To determine the appropriate management strategy, gardeners must take a closer look to ascertain the true cause of the damage.

Juniper with brown dead branch tips.  M. Grabowski, UMN Extension
Kabatina blight - Look for brown tips and dead needles on the end of branches. At the point where brown and green tissue meet, the stem is gray and small raised black spots can be seen with a hand lens. This fungal pathogen infects wounds caused by insect feeding or snow load. Branches that are 1 year old are most commonly affected and symptoms are easily seen in early spring before new growth begins. To manage this disease, clip off diseased branch ends on a cool dry day. Burn or bury infected branches.

Raised black spore producing structures of Kabatina blight. M. Grabowski, UMN Extension
Phomopsis shoot blight - Symptoms are similar to Kabatina shoot blight. Branch tips are brown with dead needles. A section of gray stem tissue is seen where the green and brown tissue meet and raised black spore producing structures occur on dead stems. This fungal pathogen infects young growing shoots and symptoms typically appear in summer after new shoots have grown 4-6 inches. To manage this disease, keep foliage dry by using drip irrigation and making sure lawn sprinklers do not wet the foliage. Do not fertilize junipers with a history of Phomopsis shoot blight. Clip off and burn or bury infected branches. If junipers have been infected with phomopsis shoot blight several years in a row, fungicides can be used to protect young green shoots in spring. Some resistant varieties are available.

Gray stem tissue divides healthy green tissue from brown needles in Phomopsis shoot blight. M.Grabowski, UMN Extension

Rodent damage - Although juniper may not seem like a tasty meal to you or I, voles and rabbits have been known to strip bark off juniper stems during winter. Look for dead needles on one or more branches. Follow this branch back into the canopy and look for scrape marks and removed bark along the branches.

Vole damage to stems resulted in dead needles. M. Grabowski, UMN Extension
Removed bark and teeth marks in the wood clearly indicate vole feeding. M. Grabowski, UMN Extension
Junipers often tolerate tip death and some branch loss. New growth fills in holes left by killed branches. Unfortunately if disease or wildlife damage is severe the juniper may never recover the desired shape. In this case, identify the cause of the problem and search for resistant varieties to use as a replacement plant.

Monday, April 27, 2015

EAB confirmed in Fillmore County

Jeffrey Hahn, Extension Entomologist

(The following information is taken from an April 24, 2015 news release from the Minnesota Department of Agriculture)

Last Friday, the Minnesota Department of Agriculture (MDA) identified an emerald ash borer (EAB) infestation in Fillmore County. Fillmore County is the eighth county in Minnesota to confirm the presence of EAB. Additionally, EAB has also been found in Ramsey, Hennepin, Houston, Winona, Olmsted, Dakota, and Anoka (which was just confirmed last month) counties.

Suspected EAB larva and feeding activity consistent with emerald ash borer was found in a boulevard ash tree in the city of Rushford. The infested tree was found through a routine visual survey of ash trees currently being conducted by the MDA. This survey is designed to find EAB in new locations at high risk for EAB infestation.
Verify EAB by finding the larvae or its tunnels
Fillmore County will likely be put under an emergency quarantine this week. The quarantine is in place to help prevent EAB from spreading outside a known infested area. It is designed to limit the movement of any items that may be infested with EAB, including ash trees and ash tree limbs, as well as all hardwood firewood.

Minnesota is highly susceptible to the destruction caused by EAB. The state has approximately one billion ash trees, the most of any state in the nation.
  • The biggest risk of spreading EAB comes from people unknowingly moving firewood or other ash products harboring larvae. There are three easy steps Minnesotans can take to keep EAB from spreading:
  • Don’t transport firewood. Buy firewood locally from approved vendors, and burn it where you buy it;
  • Be aware of the quarantine restrictions. If you live in a quarantined county, be aware of the restrictions on movement of products such as ash trees, wood chips, and firewood; and,
  • Watch your ash trees for infestation. If you think your ash tree is infested, go to the MDA EAB page and use the “Do I Have Emerald Ash Borer?” guide.
For more information about EAB, see the University of Minnesota Extension publication, Emerald ash borer in Minnesota.

The original MDA news release can be found here.

Thursday, April 16, 2015

How to find help with a home landscape

Home owners often ask Extension how to find a student, a Master
Gardener, or an industry professional to help them with a home landscaping project or garden design.  They wonder if students need projects, if Master Gardeners can do this kind of activity for their volunteer hours or how to choose a landscape professional.

Landscape professionals typically have a degree in landscape design or a related area, and /or are licensed as a landscape architect. Some garden centers offer full service landscape design, implementation and maintenance services. Homeowners can also find firms by searching the Minnesota Nursery and Landscape Association website. Use the search function to find the type of help you are looking for in your geographical location; for example, "landscape designer St. Paul, MN". Word-of-mouth is also a very good way to find a landscape professional. When you see a landscape you love, ask the homeowner for a recommendation.   

To reach students looking for seasonal work or alumni in the landscape business, post a job description on GoldPass: Job, Internship and Volunteer Listings. GoldPASS is the U of M's online database to help connect students and alumni with employers, volunteer organizations, and internships across the country. Posting is free, easy to do, and open to anyone.

Homeowners may also choose to send a job description to the Extension Master Gardener program in your county. Master Gardeners are educated by University Extension, and volunteer by teaching the general public research-based horticulture information. While Master Gardeners are volunteers and are not allowed to accept payment or work on private properties as part of their volunteer hours, some are professional gardeners, designers or landscape architects by trade. A county program may have a website or newsletter for volunteers only where such job postings can be made available.

Thursday, April 9, 2015

Back to Bleach to Keep Pruning Tools Clean

M. Grabowski, UMN Extension

When pruning out a branch infected with a fungal or bacterial plant pathogen there is a risk that the pathogen will stick to the pruning tool and spread to other trees and shrubs that the tools is used on. This risk is very low during the winter months, as many plant pathogens are dormant along with the trees. Pruning cuts made during the growing season carry a much higher risk of transferring plant pathogens on pruning tools from one plant to another.

Leaves & blossoms killed by fire blight. M. Grabowski UMN
This spring gardeners should be extra careful when pruning crabapple, apple or mountain ash trees that suffered from fire blight last year. Fire blight is caused by the bacteria Erwinia amylovora. This bacterial plant pathogen survives Minnesota’s winter in branch infections called cankers and emerges in warm spring weather in a sticky liquid called bacterial ooze. The fire blight bacteria are easily spread on pruning tools.

To avoid this problem, pruning tools used on infected trees anytime after bud break should be sterilized between cuts. In 1991, a researcher named Beth Teviotdale published a study showing that the best solutions for sterilizing pruning tools were a 1:5 solution of Pine-sol, Lysol, or household bleach and water. Rubbing alcohol (70% isopropyl alcohol) killed some but not all of the bacterial pathogens on the blade.

Unfortunately although product names remain the same, the ingredients in the bottle may change. In fact the formulations of Pine-sol and Lysol have both changed significantly since 1991. New research is needed to determine if these new formulations are effective in sterilizing pruning tools. In the meantime, a 1:10 dilution of household bleach (5.2% sodium hypochlorite) in water remains the most effective solution to sterilize pruning tools. It can be applied as a spray or by dipping or soaking the blade in the solution.  Bleach can be corrosive to metal.

Monday, April 6, 2015

Q&A: Organic Lawn Care

Question: I have read the report on but still not sure what I need to do to get rid of weeds in my lawn naturally. We have not treated our lawn for a while and now gradually grass is being replaced by clover and other weeds. Any suggestions? We would like to avoid chemicals in our yard.

Answer: Thank you for your question. The goal: keep your lawn as healthy as possible through good cultural practices. This will enable it to out-compete weeds and tolerate the heat of the summer and winter cold. Here are some steps you can take to manage weeds in your lawn without chemicals. Note that these are considered "cultural methods" of management and must be ongoing to be continually effective.

  • Re-think your idea of a "perfect lawn". Accept some non-grass plants in your lawn. Dandelions and clover are good plants for bees as they provide early season pollen and nectar.
  • Raise your mower blade to 3". Longer grass blades keep plant crowns cool, moist and less stressed during summer heat. Mowing regularly also helps to manage weeds.
  • Depending on the size of a weedy area, digging out weeds by hand and re-seeding is sometimes your only option. It is an ongoing maintenance task. You may choose to eliminate areas of grass altogether and re-plant with shrubs, perennials, and trees.
  • Water grass deeply and infrequently. The top 5-6" of soil should be moist. This will cause grass roots to move deeper into the soil seeking the water. If you water a little at a time, the water only wets the top few inches of soil. This causes the grass roots to stay at the surface of the soil - where the water is - and thus are more likely to become stressed and dry during the heat of mid-summer.
  • Avoid trying to grow grass under trees. Instead, mulch these areas and plant hardy perennials like Hosta, Heuchera (coral bells), and native wildflowers. This approach eliminates thin grass that cannot out-compete weeds. It also eliminates potential damage to tree trunks and tree roots by lawn mowers and weed whips that can lead to tree health issues. Plantings under trees also look really lovely and provide interest in the landscape.
  • Fall is a good time to aerate your lawn. Aeration removes soil plugs from the ground, lessening compaction and creating a better environment for grass roots. Local equipment rental shops have aerators or you can hire a landscape maintenance company to aerate.
  • After aerating, over-seed your lawn with a soil / compost / seed mixture. In Minnesota, we grow cool season grasses. They are most actively growing in spring and fall. Choose grass seed that is suitable for your conditions (full sun, part sun, shade, etc.). You can purchase this at a local garden center. Note that high quality seed usually costs more. Ask for help in choosing a seed mixture(s) suited to your yard. Some stores can also mix seed for you.
Be sure to continue utilizing U of M Extension Garden resources and publications for gardening information.

Thursday, April 2, 2015

Spring Preemergent Applications for Crabgrass

Every year around this time I start receiving questions regarding when to apply preemergent herbicides for preventing crabgrass establishment in lawns. Crabgrass germination is driven by soil temperatures and because of this we cannot rely on a calendar date to tell us when to apply our preemergent products. The reality is, if we wait too long and miss the window of opportunity to apply crabgrass preventers, these products will not do much for control of crabgrass. For this reason I like to rely on a couple of website resources that help to determine when to make these applications.  The first website that I like to use can be found here: This is a site operated by Michigan State University and the model uses air temperature predictors to determine when to apply crabgrass preventers. Simply select the tab "Crabgrass PRE", enter your zip code, and the map will be created.  For a more detailed explanation of how to utilize this website for crabgrass prevention, see this great post from Dr. Aaron Patton at Purdue University.

The other website that I like to use is the University of Minnesota's Climatology Working Group Site. On this site you can look up weather information including soil temperatures for your specific location in the state. Preemergent herbicides for crabgrass should be applied before soil temperatures are 55 degrees in the upper 1-2 inches for several days.

Now here's something else to think about. Crabgrass preventers that include fertilizer, like Scott's Turf Builder with Halt's Crabgrass Preventer, can be convenient for both professional turfgrass managers and homeowners. However, when using products that offer the convenience of a 2 in 1 (fertilizer with herbicide), it may be more difficult to identify an ideal timing for application. By this I mean that the appropriate time for applying a crabgrass preventer may not coincide with the time to fertilize.  Typically we suggest to apply fertilizer to your lawn when it is actively growing in the spring from mid-May to early-June. If the lawn isn't actively growing and quick release sources of fertilizer are used, there is a potential for these nutrients to be lost through leaching or runoff.  Crabgrass preventers should go down from mid-April to mid-May, which is often too early for fertilizing.  For these reasons, I suggest to use caution with these products and carefully consider when would be the appropriate time to make applications depending on where you are in the state.  Products containing slow release sources of nitrogen can be put down earlier than products with quick release sources.

Visit these resources for more information on preventing crabgrass, including identifying crabgrass and choosing herbicides from Purdue University and Dr. Aaron Patton's Program.
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