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Wasp queens active now

Jeffrey Hahn, Extension Entomologist

Jeff Hahn, University of Minnesota

Photo 1: Yellowjacket queens are occasionally found indoors during early spring

Now that spring has finally arrived, much to our relief, we may need to deal with insects that have been overwintering within our homes. This includes yellowjackets (Vespula spp. and Paravespula spp.) and paper wasps (Polistes spp.). Once freezing temperatures arrived last fall, the old queen and all the workers in nests died. The only survivors were the queens that were produced during late summer.

After these new queens mated, they left their nests and started looking for sheltered, protected sites to spend the winter, much like boxelder bugs or lady beetles. These sites include firewood, loose bark on trees and logs, brick piles, under leaves, as well as in and around buildings. The wasp queens remain inactive until it starts to warm up during late winter and early spring. When queens overwinter in homes, they can also become active when mild temperatures occur during mid-winter.

Jeff Hahn, University of Minnesota

Photo 2: Many paper wasp queen can sometimes be found in homes during early spring

Once active, wasp queens leave their overwintering sites and start to look for an appropriate place to begin a new nest. If they are in buildings, they usually become trapped. Finding wasp queens in homes and other buildings during early spring does not mean a nest is present. While only one or two yellowjacket queens at normally seen at a time, it is possible to see a larger number of paper wasp queens as they like to overwinter gregariously, i.e. in non-social groups.

Physical removal is the only necessary control for wasp queens found indoors. They are just a nuisance and do not indicate a bigger problem. Use a jar or some sort of container to remove and release them outside. If they are by a window or door, just open it up and let them fly out. Killing and removing queens is also an option. This is a temporary problem that will go away on its own.


Surprise! It's snow mold!

Michelle Grabowski, UMN Extension Educator

M. Grabowski

Many Minnesotans have anxiously awaited snow melt this spring. The joy of seeing green grass again may be coupled with the disappointment of snow mold. Lawns affected by snow mold have round to irregular patches of matted down tan to gray turf grass. If a light drizzly rain is present or humidity is high at low temperatures, cobweb like fungal mycelia may be seen growing across the infected turf grass.

This winter's heavy wet snow layer has provided ideal conditions for the fungal pathogens that cause snow mold. These fungi thrive at temperatures just around freezing. Persistent snow or cool rainy weather provides the humidity and temperatures needed by the fungi to thrive.



M. Grabowski


Photo 2: Fluffy fungal growth on a snow mold patch on a cool rainy day


In spring the best management strategies for dealing with snow mold of a home lawn include removing heavy snow from valuable turf areas, raking up matted down turf grass to improve air circulation and drying of infected patches, and removing any leaf litter or other plant debris that may have accumulated on the lawn. Sunny weather and warming temperatures will favor growth of the turf grass and most lawns recover. In severe cases, the center of the snow mold patch may need to be reseeded.

April 2nd 2014 Issue

Had enough of the Snow?

Karl Foord, Extension Educator - Horticulture

Karl Foord

Photo 1: No snow

Karl Foord

Photo 2: Snow stopped

Karl Foord

Photo 3: Snow slowed

Last Thursday March 27, 2014 I watched the largest snowflakes I had ever seen come drifting down onto our Minnesota landscapes. Did you find yourself in this type of show shower?

Snowflakes are composed of 6 sided snow crystals. When the temperature in the troposphere (the lowest layer of earth's atmosphere) is significantly below freezing, the snowflakes created under these conditions are small and termed dry snow. When the temperature in the troposphere is close to freezing, the snowflakes melt enough to create a water film enabling flakes to stick together.

Other sources have reported the Guinness Book of World Records to have the largest reported snowflake ever at 15 in. wide by 8 in. thick. This observation was made by a rancher in Fort Keogh, Montana on January 28, 1887. I tried to confirm this on the Guinness website but a search under snowflake returned zero results. However in the letters to the editor section of the periodical Nature from 1887 (vol. 35,p. 271) snowflakes up to 4 inches across were observed on January 7, 1887. This was done by catching the flakes on circular glass plates chilled for the purpose. These large flakes only fell over a 3 minute period.

Another way to measure these flakes with some form of accuracy is to create a grid on a dark piece of paper. If the grid is made up of 1 cm squares then a reference exists to reference the size when the flake falls on the paper. One would need more than an 8.5 x 11 sheet of paper to catch a Guinness record. I attempted to photograph this event. Photo 1 shows the view without snow. Photo 2 shows the view with snow, and photo 3 shows the snow captured at a shutter speed of 1/30 of a second so the length of the streaks shows you how far the snow moved in that time period. Photo 2 was taken at 1/640 of a second.

Granted this is not exactly horticulture, but I thought this might be a good if not whimsical way to usher out this year's snow as we anxiously await spring.

Karl Foord, Extension Educator - Horticulture

Karl Foord

Photo 1: Buds of Austrian Pine (Pinus nigra)

Karl Foord

Exhibit 2: Healthy buds of Swiss Stone Pine (Pinus cembra)

Karl Foord

Exhibit 3: Dead buds of Swiss Stone Pine (Pinus cembra)

Karl Foord

Exhibit 4: Buds of Korean Fir (Abies koreana)

Kathy in her article on winter burn states the following:

Wait until spring before deciding how to care for your winter burned plants. If leaves are dead but buds and stem tissue near dead foliage are still alive, new plant foliage will regrow to replace winter burned foliage.

I had significant winter burn damage on the following: all hemlocks (Tsuga canadensis), Austrian pine (Pinus nigra), and Scots pine (Pinus sylvestris), Swiss stone pine (Pinus cembra), and Korean fir (Abies koreana). I had little or no damage on the following: Mugo pine (Pinus mugo), Japanese white pine (Pinus parviflora, Glauca group), Limber pine (Pinus flexilis), Taylor's Sunburst (Pinus contorta), and Uncle Fogy pine (Pinus banksiana).

Following Kathy's lead I looked at the buds of some of these plants.

The buds on the Austrian and Scots Pines looked healthy (Photo 1 of Austrian pine buds). There were healthy and dead buds on the Swiss stone pine (Photos 2 & 3) as there were on the Korean fir (Photo 4). The bud sizes are quite different with the one on the right looking more robust.

As Kathy said we will just have to wait and see, but having a close look at the buds gives you a sense of what to expect. Frankly I hope your evergreens overwintered better than mine.

Current Insects: April

Be on the watch for these insects in April

Insects in and around Homes

• Ants

    °  carpenter

    °  cornfield, pavement, pharaoh, yellow, thief, odorous house, field, acrobat

    °  winged ants: carpenter, pavement, yellow, false honey

  Beetles

   °  carpet beetles

   °  lady beetles, multicolored Asian 

   °  larder beetles 

   °  see also stored product insects below

  (True) Bugs

   °  boxelder bugs

   °  hackberry psyllids

   °   western conifer seed bugs

  Cockroaches

   °  German, brownbanded, American, Oriental

   °  Pennsylvania wood cockroaches (found indoors or outside in wooded areas)

   Flies

    °  blow flies

    °  cluster flies

   °  fruit flies

   °  fungus gnats

   °  moth flies

   °  phorid flies (also called humpback flies)

•  Springtails

•  Stored product insects

   °  Indianmeal moths

   °  flour beetles, sawtoothed grain beetles, cigarette beetles, drugstore beetles etc.


•  Wasps (including yellowjackets)

•  Non-insect arthropods

   °  spiders  

  °  house centipedes

  °  pseudoscorpions

  °  millipedes

  °  sowbugs 

Insects in Gardens
•  Andrenid bees

•  Common asparagus beetles (first active late April to early May)

•  Iris borers (eggs hatch late April to early May)

•  Root maggots (adults first active late April to early May)

Insects in the Landscape 

•  Clover mites

•  Eastern tent caterpillars (eggs hatch late April to early May)

•  Nightcrawlers

Insects and relatives that bite or sting



Winter Burn on Minnesota's Evergreens

K Foord UMN Extension

Photo 1: Browning

K Zuzek UMN Extension

Photo 2: Bleaching on 'Green Mountain' boxwood

J Weisenhorn UMN Extension

Photo 3: Snowline winter burn

Evergreen trees and shrubs provide a lot of interest in our landscapes during Minnesota's long winters. Boxwood and rhododendrons are examples of the few broadleaved evergreens grown in Minnesota. Most of our evergreen species are narrow-leaved conifers - pine, spruce, arborvitae, juniper, hemlock, and yew - that have needles or scales for foliage. Unfortunately all of these species can be injured by winter burn and the winter of 2013-14 is proving to be no exception. Winter burn injury has been observed on many evergreen trees and shrubs. As we move from late winter into early spring and temperatures continue to increase, more of this damage will probably appear and existing damage will become even more dramatic.

Symptoms of winter burn are browning (Photo 1) or bleaching (Photo 2) of foliage, particularly on the south, southwest, and windward sides of plants. Evergreen foliage buried under snow is usually protected from damage while plant parts above the snowline are often damaged (Photo 3). In severe cases, the entire plant may turn brown and die. Sometimes symptoms occur immediately as damage occurs, but often symptoms appear or worsen as temperatures rise in late winter and early spring.

Winter burn results from water loss in plants during winter.

During the growing season, water is absorbed and pumped from soil into the roots of plants. From there, streams of water are suctioned up into a plant. Some of this water is used for plant growth and reproduction. But the vast majority is lost during transpiration as water is released back into the atmosphere through small openings called stomates on the lower surface of leaves. This lost water is quickly replaced as roots continue to absorb and pump water from soil into plants.

As plants acclimate and prepare for winter, deciduous trees and shrubs drop their leaves with their thousands or millions of stomates. But because evergreen woody plants retain their foliage, transpiration and loss of water from stomates continue during winter. This is especially true on sunny and windy winter days when higher temperatures and wind speeds increase transpiration rates. Because roots in frozen soil have no ability to replace this water, winter burn occurs as leaves desiccate, die, and turn brown. In more severe cases, buds, stem tissue, or entire plants may die.

Wait until spring before deciding how to care for your winter burned plants. If leaves are dead but buds and stem tissue near dead foliage are still alive, new plant foliage will regrow to replace winter burned foliage. On the other hand, if buds and stem tips were damaged, branches should be pruned back to ¼" above a bud in the live portion of the plant. In severe cases the entire plant may have died and plant removal and replacement will be necessary.

K Zuzek UMN Extension

Photo 4: Burlap protection

To prevent winter burn in the future:


  • Keep evergreens properly watered throughout the entire growing season until ground freezes. Initial soil freeze in Minnesota typically occurs in late November and early December .

  • Maintain a 3-4" layer of organic mulch around evergreens to help retain soil moisture throughout the growing season. As this mulch breaks down, it will also improve your soil's moisture holding capacity.

  • Protect plants in highly exposed sites during winter with burlap (Photo 4), lathing, snow fencing, or other materials to prevent too much exposure to sun or wind.

  • During future planting, properly place evergreens in the landscape by planting them on the eastern or northeast sides of a building. Avoid planting evergreens on the south or southwest sides of buildings or in any site with high exposure to winter sun and wind.

  • Plant evergreens in spring and water them consistently throughout the growing season so that they can use the entire growing season to establish well and expand their root system and water-absorbing capacity.

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