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Showing posts from June, 2010

Sapwood Rotting Fungi Kick Trees When They Are Down

Michelle Grabowski, UMN Extension Educator

Photo 1: Canopy dieback caused by sapwood rotting fungi Photo by M.Grabowski UMN Extension.When shade trees are stressed by environmental conditions or wounded by storms, ice, insects, sunscald or mechanical damage, sapwood rotting fungi often show up to take advantage of the trees weakened state. There two sapwood rotting fungi commonly found in Minnesota, Schizophyllum commune or Cerrena unicolor. These fungi infect the tree through wounds. They then rot the sapwood and kill the bark. When severe, the infection can grow to completely encircle a branch or the main trunk, killing all leaves and branches above the infected area.

Sapwood fungi infect a wide variety of common shade trees. Maple (Acer), linden (Tilia), willow (Salix), elm (Ulmus), oak (Quercus), ash (Fraxinus), poplar (populus), and many more may all suffer from this disease.

How to Recognize Sapwood Rotting Fungi
Gardeners often first notice dead branches throughout the canopy of i…

Summer Lawn Care on the Heels of a Wet and Stormy June

Bob Mugaas, UMN Extension Educator

With the recent rains and storms across the state, most lawns have had sufficient moisture to remain actively growing and green through the month of June. In fact, in some instances there has been too much rain causing lawns to remain in excessively wet conditions for several days or more at a time.

Under moderate temperatures and partly sunny or cloudy conditions, water that temporarily (a day or two) remains at or near the lawn surface is usually not a problem. (See Picture 1). Once the water drains away and soil oxygen levels rise such that normal root functions can continue, the grass will resume normal activity and growth with little to no evidence of having been temporarily submerged. However, under sunny conditions and high temperatures, lawn areas remaining in saturated soil conditions or submerged for even a few hours can suffer serious damage and even death. Once the moisture does recede, grass plants will appear dark brown to black…

Birch Erineum Gall

Jeffrey Hahn, UMN Extension Entomologist

Some birch trees are exhibiting red, fuzzy patches on some of their leaves. It is common to assume that this is a type of disease but it is actually a type of gall. Galls are abnormal plant growths due to a variety of different organisms. In this case is caused by a species of eriophyid mite. Eriophyid mites are very tiny and nearly microscopic. This gall is similar to ones found on maple, viburnum, and linden. Like other insect and mite leaf galls, birch erineum galls have very little, if any, impact on tree health. You do not have to do anything if you find this gall in your tree, just ignore it.

Strawberry Root Weevils

Jeffrey Hahn, UMN Extension Entomologist

Strawberry root weevils have been common around homes lately. This insect is about 1/4th inch long, reddish brown to dark brown to black in color. They are bulb-like in shape with rows of shallow pits running down their back. They have a conspicuous pair of antennae which can look like a pair of legs. This could be why some people confuse these insects for ticks. However, when someone says they have ticks in their house, double check for the presence of strawberry root weevils.

Despite their name, the larvae actually feed on the roots of a variety of plants including strawberry, arborvitae and other evergreens, raspberries, and grapes. The adults notch feed along the edges of leaves. However, despite this feeding, strawberry root weevils are not considered a plant pest in Minnesota.

It is common for strawberry root weevils to enter homes looking for moisture. They are commonly found around sinks, basins, and tubs. Fortunately, strawberry root w…

Earwigs Are Active Now

Jeffrey Hahn, Extension Entomologist

People have been commonly reporting European earwigs recently. An earwig is about 5/8 - 3/4 inch long, with a flat, reddish brown body and very short wings. They are beetle-like and are sometimes confused with cockroaches. However, it's easy to identify an earwig as they have forcep-like pincers on the tip of its abdomen: males have stout, curved pinchers while females possess more slender, straight pincers. Despite these pinchers, earwigs are harmless to people and our property.

Earwigs love to be in dark, confined, damp areas and are found under potted plants, leaves, welcome mats, in cracks between pavers and similar places. They may also be found on plants in tight, protected areas. They are mostly active at night when they feed on decaying plant tissue, live and dead insects, as well as live plants. Occasionally, earwigs can be a pest when they feed on flower blossoms. They are also reported to attack corn silk and seedlings.

People are m…

July 2010 Garden Calendar

- Time to set out apple maggot traps in apple trees.

- Strawberry picking is just beginning in the north, and starting to wind down in the south.

- Raspberry picking is underway.

Spotted at the Arboretum: Canada Geese and Wild Turkey

Photo credits: Karl Foord

Yard and Garden News Editor: Karl Foord, UMN Extension Educator
Technical Editor: Bridget Barton

Peony Flower Types

Karl Foord, UMN Extension Educator

I just finished photographing the peony collection at the Minnesota Landscape Arboretum and was amazed at the variety of flower types and colors. Peony flower types fall on a continuum starting with single and progressing through semi-double, Japanese, and double. The single flower has a central cluster of carpels surrounded by a ring of stamens surrounded by a ring of petals, a basic flower structure. The following flower types all have modifications of this basic structure. The semi-double flower may have a fertile center surrounded by several layers of petals. "Japanese" peonies have modified stamens (staminoides) which may have some functional anther material and pollen, but the stamen filaments are now more like petals. In double peonies all flower parts are petals.

According to some estimates, there are over 3,000 cultivated varieties of peony.

To identify peonies, a fairly comprehensive list is available at - …

What's Happening in the Orchard?

Karl Foord, UMN Extension Educator

Photo 1: Strawberry field showing some almost ripe berries and developing fruit.


Pick-your-own strawberries should be in full swing as of this writing. The picture below was taken at Apple Jack Orchards in Delano on June 10, 2010. Don't miss the opportunity to taste fresh strawberries. You can find a strawberry field near you by going to entering your location and clicking on the strawberry button. The Minnesota Grown Strawberry fields will be listed in order based on proximity to your location.


Continue to protect your small young apples. I found damage from a few green fruitworm as well as plum curculio. Plum curculio causes feeding and egg laying damage to young apple fruit. Practice sanitation and remove all infected fruit. Do not let the fruit fall to the ground permitting the curculio larvae to burrow into the soil pupate and come back next year in greater numbers.

Some minor damage…

Gray Mold

Michelle Grabowski, UMN Extension Educator

Recent wet weather has provided perfect conditions for a common fungal disease of flowering annuals known as gray mold. Gray mold is caused by the fungus Botrytis cinereaPhoto 1: Gray mold from an infected flower moves to leaves M.Grabowski UMN Extension. and can occur in a wide variety of annual flowers including impatiens, zinnias, geraniums and many more.

Photo 2: Brown leaf spot from gray mold infection M.Grabowski UMN Extension.Often called Botrytis blight, gray mold causes a dark brown to black blight of flowers, buds, leaves and stems. Flower petals are especially susceptible to infection by the gray mold fungus. Brown spots may be seen on petals or the entire flower may turn brown. As flowers age, they fall off onto healthy leaves below. The gray mold fungus then infects the leaves. Removal of these rotted petals often reveals a brown target shaped spot on the leaf which quickly grows to rot the entire leaf. With high humidity a cloud …

Prepare For Mosquito Season

Jeffrey Hahn, UMN Extension Entomologist

With the rains that have fallen on most of Minnesota recently, you can expect the number of mosquitoes to significantly increase. However, keeping away from these blood-lusting insects is easier said than done. The bites are bad enough but we also have to worry about mosquito transmitted diseases, especially West Nile virus. There are certain precautions you can take to protect yourself when you are in mosquito-infested areas. You can minimize your exposure by avoiding times when mosquito activity is the highest, i.e. dawn and dusk and also wear long-sleeved shirts and long pants.
However, the best method for protecting yourself from mosquito bites is using a repellent. The Centers for Disease Control and Prevention (CDC) recommends several repellents that you apply to your skin and clothes for mosquito control. The best overall repellent has traditionally been DEET (N,N-diethyl-m-toluamide). DEET has been available to the public since 1956 and…

Watch For Meal Moths

Jeffrey Hahn, UMN Extension Entomologist

There have been a number of reports of meal moths in homes recently. When at rest, the forewings of this moth have a dark reddish brown band across the top and bottom of the wings while there is an olive or yellowish green band, outlined by wavy white lines in the center. They have a wingspan of about 3/4 - 1 inch. Their abdomen is typically curved up at a 90o angle when at rest.

Meal moths are not as common as Indianmeal moths, although they both feed on dried food products. Meal moths are known to feed on flour and grain products, seeds, and hay especially when they are damp. These moths are generally not common in homes but are more typically found in mills, barns, and warehouses.

If you do find meal moths in your home, the best control is to find the source of the infestation and remove it. Look where you store dried food products. Don't forget about places where grain and flour products, bird seed and other types of seeds, and dried p…

Cutworms Common This Spring

Jeffrey Hahn, UMN Extension Entomologist

Cutworms have been a very common insect problem in many home gardens this year. They have also been commonly reported in Wisconsin and Iowa as well. Most of the cutworms that occur in Minnesota overwinter as large larvae. It has been speculated that the heavy snow cover we experienced this spring increased the survival of the overwintering cutworms. That coupled with the early spring allowed them to occur early in the season. There are some non-native cutworms, e.g. black cutworms, that move up to Minnesota from the south, but they did not appear to have been as damaging this year.

Cutworms hide during the day in the soil near the plants, then feed on plant stems at night. Their damage is most severe right away in spring when plant stems are more tender but not a problem later in the summer. Unfortunately, it's too late to manage cutworms any longer this year. That cutworms were very common this year does not necessarily mean that they will…

Ash Anthracnose or Emerald Ash Borer?

Michelle Grabowski, UMN Extension Educator and Jeff Hahn, UMN Extension Entomologist

With the discovery of emerald ash borer (EAB) in Minnesota in 2009, many homeowners are keeping a close eye on the ash trees on their property. This has resulted in a great deal of concern as many ash trees began to drop their newly formed leaves early this spring. In most cases, however, the cause of this early leaf drop was a common fungal disease known as ash anthracnose.

Emerald Ash Borer

If a tree is suffering from infestation with EAB, the tree's canopy will appear thin, with few to no leaves. Eventually dead branches will be noticed within the tree. Cracks and D shaped exit holes can be found in the bark of infested trunks, and woodpeckers may be noticed frequently visiting infested trees to feed on EAB larvae. The emerald ash borer itself is a slender, ½ inch long, iridescent green beetle. It is active anytime from late May into August.
Ash Anthracnose

In contrast, trees infected with ash a…

What's Happening in the Orchard?

Karl Foord, UMN Extension Educator

As you know, this has been another unique spring for Minnesota. We started out several weeks ahead of normal and lost some ground with a cold spell. Unfortunately, in some areas the cold spell was more than a delay. In certain parts of the state the nighttime lows on May 9th reached 25.5 degrees F.


Strawberry flowers are most vulnerable to frost damage when fully open. At this growth stage 30 0F will damage the flowers. The fruit can tolerate a few more degrees and sees damage at and below 28 0F. A "popcorn" stage closed flower bud shows damage at 26.5 0F and a tight bud at 22 0F. A damaged strawberry flower will turn black in the middle whereas a healthy flower will be yellow in the middle (Photo 1). This frost damaged open flowers and some "popcorn" flowers. All is not usually lost with strawberries as they flower over a two to three week period (note the variation in stage from open flower to young fruit (Pho…

Flowering Lawn Grasses Create Curiosity and Concern Among Homeowners

Bob Mugaas, UMN Extension Educator - Horticulture

Minnesota lawn grasses are known as cool season grasses as their peak periods of growth and activity occur during the (usually) cooler seasons of spring and fall. These grasses include Kentucky bluegrass, fine fescue, perennial ryegrass and tall fescue. The middle of May through most of June is the prime flowering period for these cool season grasses in Minnesota. Kentucky bluegrasses tend to be the first of the grasses to begin flowering with the fine fescues, perennial ryegrasses and tall fescue coming on slightly later. See Picture 1 of Kentucky bluegrass flowering.

Grass flowering is an entirely normal process whether observed in a mowed lawn or an unmowed area. However, the height of the flowering stem will usually be slightly to significantly taller in an unmowed situation than a mowed lawn. The initiation of the flowering process actually begins late the previous fall when the growing point (crown) of a mature grass shoot goes t…