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Showing posts from June, 2013

Stag Beetles in Yards

Jeffrey Hahn, Asst. Extension Entomologist



Jeff Hahn
Photo 1: Stag beetles. Note the large mandibles.

People have been finding stag beetles in their yards and gardens recently, sometimes in large numbers. Also known as pinching bugs, these beetles typically measure a little more than one inch in size and are reddish brown to dark brown in color. Stag beetles resemble June beetles but have more prominent heads. The mandibles (jaws) of both sexes are also large and conspicuous, especially those of males. Stag beetles have short antennae with conspicuous asymmetrical plates (lobes) at the end of them which they are not able to close together. One of the most common species in Minnesota is Lucanus placidus.

All stag beetle larvae feed in dead or decaying wood, such as logs and stumps. Most adults emerge in May or June and feed on sap that exudes from plants. Stag beetles are active at night and are often attracted to lights. They can fly into a yard, land on the ground and remain th…

Impatiens downy mildew already making an appearance in MN landscapes

M. Grabowski
Photo 1: Impatiens showing symptoms of downy mildew

Michelle Grabowski, UMN Extension Educator


The extended cool wet weather present throughout much of Minnesota has brought out the symptoms of impatiens downy mildew early this year. Plants infected with impatiens downy mildew drop their blossoms and have yellow stippled leaves that curl under at the edges. As the disease progresses, infected leaves fall off, leaving barren green stalks, which flop to the soil like cooked spaghetti noodles with time. Plants that are infected very young often remain small and yellow, dropping leaves and collapsing before they can ever grow to maturity.

The pathogen responsible for impatiens downy mildew is Plasmopara obducens, a water mold that thrives in cool wet conditions. Spores of the pathogen can be seen as fluffy white growth on the lower surface of infected leaves. These spores are easily spread on wind and splashing rain.



M.Grabowski, UMN Extension
Photo 2: Sporulation of downy mild…

Protect Yourself from Mosquitoes

Jeffrey Hahn, Asst. Extension Entomologist

A benefit of our cold, late spring has been that the primary biting mosquito in Minnesota, Aedes vexans, was delayed in its emergence until early June. However, they are out now and if you spend any time outside, they will find you sooner or later. Mosquitoes have been particularly abundant this year because of the frequent rainfalls we have received. As long as we received regular rain, we can expect to continue to battle mosquitoes. In addition to the annoyance of their bites, mosquitoes are capable of transmitting diseases to people, especially west Nile virus (there were 70 cases in 34 counties in Minnesota last year including one death) and Lacrosse encephalitis.


Jeff Hahn
Photo 1: Mosquitoes are abundant when we have a lot of rain.


It is challenging to completely avoid mosquito bites but there are some steps you can take to minimize your exposure to them. It is important to remove or drain potential breeding sites for mosquitoes. …

All things BUGS! Jeff and Julie on WCCO radio "Smart Gardens" - 6/22, 8am

Something "bugging" you????? Join Julie Weisenhorn and special guest extension entomologist, Jeff Hahn, this Saturday, 8-9am, on WCCO Radio's "Smart Gardens" (830 AM on the dial). This is your opportunity to get Jeff's help in solving those pesky pest questions. Listeners can call or text in questions for Jeff and Julie.

About the show: WCCO Radio has teamed up with U of M Extension to bring you "Smart Gardens" which airs every Saturday from 8-9 a.m. If you have something to say, call-in at 651-989-9226 or text 81807. For more info and podcasts: WCCO Smart Gardens.

What the Heck is a Hellgrammite?

Jeffrey Hahn, Asst. Extension Entomologist



Andrew Williams
Photo 1: Hellgrammite, the larva of a dobsonfly

Some residents have been recently encountering a large (and to some people a scary) insect larva. This dark colored insect, a hellgrammite (Corydalus cornutus), has an elongate and somewhat flattened body. It has six conspicuous legs as well as a series of filaments on the sides of its abdomen with small finger-like gills clustered at the base. A hellgrammite also has very prominent, strong mandibles (jaws). It reaches about two to three inches in length when fully grown. Despite its appearance, hellgrammites are not aggressive or dangerous to people, although it is possible that they can bite if they are handled carelessly.

A hellgrammite lives in running fresh water, such as streams or rivers, often hiding around rocks or debris. They are predaceous, feeding on insects and other aquatic invertebrates. They have the interesting ability of being able to swim backwards as w…

A Different Way to Protect your Apples from Apple Maggot

Karl Foord - Extension Educator, Horticulture

Apple maggots are predicted to emerge in the beginning of July so this is a good time to consider protective strategies.



Karl Foord
Photo 1: Apple fruit prior to thinning




Apple maggot flies recognize and identify apples through a series of visual and chemical clues. The red sphere traps and the yellow square traps both covered with a sticky substance as well as scented lures aid in capture of apple maggot flies and will indicate their presence. However, it is unlikely that such traps will effectively protect your apples.






Karl Foord
Photo 2: Apple fruit after thinning




I have tried plastic bags which can work although they make the tree look phantasmagorical (i.e. nightmarish - please forgive - I always wanted to use that word in a sentence). I have also found that they can collect water and if faced toward the south can heat up and cause damage to the apple skin.





Karl Foord
Photo 3: Apple fruit with maggot barrier I



So this year I am tryin…

Bright orange slimy fungus in junipers

M. Grabowski, UMN Extension
Photo 1: Cedar Apple Rust Gall on Juniper

M. Grabowski, UMN Extension Educator

There is nothing that catches the eye so much as a bright orange slimy tentacle-like fungus hanging from a landscape juniper tree. What is that thing? you might ask. The answer is cedar apple rust, one of several Gymnosporangium rust fungi that infect junipers in the state of Minnesota. Gymnosporangium rust fungi are unique in that they spend part of their life infecting juniper trees, causing unusual brightly colored galls, and the other part of their life infecting leaves, fruits, and green stems of trees or shrubs in the Rosaceae family. The Rosaceae family includes crabapples, hawthorns and serviceberry. Different Gymnosporangium rusts infect different trees and shrubs.

On junipers, the cedar apple rust results in brown woody galls that can grow to over an inch in diameter. With wet weather, the galls produce bright orange tentacle like spore producing structures. These release …

Anthracnose of shade trees thrives in cool wet spring

M. Grabowski, UMN Extension
Photo 1: Anthracnose on Maple

M. Grabowski, UMN Extension Educator


As cool wet weather persists in Minnesota this year, a common leaf blight disease of shade trees known as anthracnose thrives and spreads. Anthracnose is a fungal disease that causes leaf blotches, leaf distortion, shoot blight, and leaf drop. This disease is caused by several related fungi that thrive in cool wet conditions. Ash, maple and oak trees are all commonly infected with anthracnose and symptoms of the disease have been seen on all of these trees this spring. Despite blackening of leaves and shoots, anthracnose actually only results in a minor stress on the health of the tree. Only young growing leaves and shoots are susceptible to infection. Mature leaves are relatively resistant to the disease. Once warm dry weather arrives in Minnesota, leaves will mature and trees will replace lost leaves with a new flush of growth. As long as cool wet weather persists, however, expect this fung…

Using Extension Information and the Pesticide Label to Safely and Correctly Solve a Pest Problem

Karl Foord - Extension Educator, Horticulture

This spring I noticed the black color on the branches of my Taylor's Sunburst Pine (Pinus contorta 'Taylor's Sunburst'). I remember seeing the same thing on my Uncle Fogy Jack Pine (Pinus banksiana) last year. The cause was the same in both cases Sooty Mold that has formed on the honeydew secretions of the Pine tortoise scale (Toumeyella parvicornis). To confirm this I went to the What's Wrong with My Plant Diagnostic Tool via the Extension Garden web page/Pest Management/Diagnose a Problem link. I tracked through "Evergreen Trees and Shrubs" to "Pine" to Black powdery coating on "needles" and "shoots". This confirmed the Sooty Mold. I also tracked through "Sticky substance coating needles" to confirm the Pine tortoise scale as the culprit.


Karl Foord
Photo 1: Uncle Fogy Pine (Pinus banksiana 'Uncle Fogy'



The scale organism put such stress on my Uncle Fogy Pine …