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August 2013 Archives

Watch out for Yellowjackets!

Jeffrey Hahn, Extension Entomologist

Jeff Hahn

Photo 1: Yellowjacket leaving the entrance of an aerial nest. Note black and yellow coloration

This is the time of year when yellowjacket nests are reaching their maximum size and become conspicuous to residents. Two sites where yellowjackets are most problematic are nests that are in the ground and those that are in hidden voids in buildings. A lot of people have mistakenly identified yellowjackets as bees (perhaps because of all of the recent discussion of bees in the media) and are looking for information on how a yellowjacket nest can be moved and saved. Yellowjackets are not important pollinators and it is not necessary to take extraordinary measures to save them. There are not any services that will remove a yellowjacket nest and relocate it.

Jeff Hahn

Photo 2: Honey bee. Note the brown and black body. Don't confuse honey bees with yellowjackets!

Yellowjackets are about ½ inch long, black and yellow, and with few hairs on their body. While honey bees are a similar size, they are mostly a golden brown with black stripes on their abdomen and hairy. While yellowjackets are very common around structures, honey bees are rarely found around homes. Correct identification of stinging insects is further complicated as many people call yellowjackets and wasps bees. Be sure your insects are correctly identified so you know the correct course of action to take (if a nest found around a home is actually turns out to be a honey bee colony, contact the Minnesota Hobby Beekeepers Association for help in removing them).

When yellowjackets are found nesting in the ground, they are challenging to control as you do not actually see the nest, just the burrow entrance that will lead to it. It is tempting to use an aerosol 'wasp killer'; however the insecticide does not get into the nest and has minimal effect on the yellowjackets flying back and forth.

Jeff Hahn

Photo 3: Ground-nesting yellowjacket nest. You only see the burrow entrance but not the nest itself.

The most effective means of controlling a subterranean nest is with a dust labeled for ground dwelling insects, although there is generally not any product like this available to the public. Another option is to use a liquid insecticide, pouring it into the nest entrance, but this is less effective. If you do attempt control, apply it at the entrance of the nest at night when yellowjackets are less active. Check after a day to see how effective the treatment was and repeat if necessary. If you are not successful yourself, then consider hiring a pest management service to treat the yellowjackets for you.

Yellowjacket nests that are found inside homes in wall voids, attics, concrete blocks, or similar spaces are equally or even more challenging. You cannot see the nest, similar to a subterranean nest, but you can see the workers flying in and out of an opening or crack. A dust labeled for use in homes would ideally be the most effective method but these products are generally not available to the general public.

Photo 4: Hidden yellowjacket nest. This is best left to a pest control service to eliminate.

An aerosol insecticide, while readily available, is not very effective. In fact, sometimes an aerosol spray can cause the yellowjackets to look for another way out, which often leads them to the inside of the home. Also, don't seal the nest opening until you know all of the yellowjackets are dead as you can cause the same reaction. The best method to control hidden nests in buildings is to have a professional pest management company treat the nest.

Ultimately, yellowjackets do not survive the winter. If a nest can be ignored until freezing temperatures arrive, all of the workers and the queen will die. The only survivors are the newly mated queens which have already left the nest. They will seek out sheltered sites in which to overwinter. Next spring, they will start their own nests in different sites (old nests are not reused). 


Cicadas are common now

Jeffrey Hahn, Extension Entomologist

Dan Mullen

Photo 1: Dog day cicada, also called annual cicada.

Many people are noticing cicadas now. Despite their appearance, they are harmless to people and property. An adult cicada is a large, one inch long, stout insect with a green or brown body with black markings. Cicadas have four fly-like wings; the first pair is much longer than their abdomen which they hold tent-like over their bodies. They also have very short antennae.

There are two basic types of cicadas, dog day (also called annual) and periodical cicadas. Dog day cicadas, Tibicen spp., do not have a synchronized life cycle so there are some that emerge every year in Minnesota. Periodical cicadas which do not occur in Minnesota spend 13 or 17 years as a nymph in the ground and then emerge together in tremendously large numbers.

While cicadas are present here from July into September, they are more often heard than seen. They produce a high-pitched sound during the day that resembles a powerline hum. Only the males produce this sound in order to attract females. They produce this hum by vibrating a membrane in an internal air chamber.

Jeff Hahn

Photo 2: Cicada nymph climbing up a tree to prepare for its final molt.

More commonly, people see the immature nymphs. They are dark brown and similar in appearance to the adults except that they lack wings. Some people think they look like beetles (perhaps because of their stout shape and that they lack wings) The nymphs are subterranean during their lives spending four to eight year underground feeding on tree roots.

Once they emerge from the ground, they climb up objects such as trees, posts, fences, and even the sides of buildings to finish their development. When cicada nymphs molt into adults, they leave behind 'cast skins'. Sometimes it is not until these empty shells are closely examined that some people realize that these are no live insects.

Fortunately, cicadas are not harmful or dangerous to people, pets, or property in any stage. While they do feed on trees, they do not cause any noticeable injury. If you see cicadas, just ignore them and they will eventually go away on their own. No control is necessary.

Jeff Hahn

Photo 3: Cicada 'cast skin'.

M. Grabowski, UMN Extension

Photo 1: Elm tree killed by Dutch elm disease

Michelle Grabowski, UMN Extension Educator


Dutch elm disease (DED) is a fungal disease that results in yellowing, wilting and browning of leaves, death of branches and eventually death of the entire tree. Today, the disease can be found in every county in Minnesota yet it is estimated that 1 million elms still remain within communities. Several management strategies have been developed that allow elms to survive if properly cared for. Elm trees can be protected from DED through fungicide injections, infections can be removed and treated if caught early, and new cultivars of elm offer resistance or tolerance to DED. To learn more on how to identify and manage the disease read the new UMN Extension publication on Dutch elm disease.

Aster Yellows in 2013

Michelle Grabowski, UMN Extension

M.Grabowski, UMN Extension

Photo 1: Purple cone flowers infected with aster yellows

Many gardeners had never heard of the plant disease called aster yellows before 2012. As summer progressed, however, flowers on purple cone flowers open up to green spikey alien like blossoms, carrots were thin, hairy and bitter when dug up and plants from onions through tomatoes turned a sickly shade of yellow. The plant disease aster yellows was responsible for all of this.


Aster yellows is caused by a phytoplasma, a small bacteria that lives only within the vascular system of a plant or within the aster leafhopper that carries it from plant to plant. Once a plant is infected, the aster yellows phytoplasma moves systemically through the plant, infecting every part from the roots through the flowers. Symptoms of the disease include yellowing of leaves and stems, unusual flower formation and clusters of weak stems known as witches brooms. The aster yellows phytoplasma can infect over 350 plants including many common vegetables, flowers and weeds. Once a plant is infect, it can never be cured.

M.Grabowski, UMN Extension

Photo 2: Petunias with yellow leaves and small discolored flowers from aster yellows

In 2012, unusually high numbers of aster leafhoppers migrated into Minnesota from southern states where they overwinter. Many of these leafhoppers were carrying the AY phytoplasma. As a result exceptionally high rates of aster yellows was seen throughout Minnesota.


So what is the status of aster yellows in Minnesota in 2013. Happily there have been significantly fewer reports of disease throughout Minnesota in 2013. This is likely due to a combination of factors. Aster yellows can survive Minnesota's winter in perennial plant parts like the crown of an infected purple cone flower. Gardeners that did not remove infected perennials last year may see symptoms again this year. The aster yellows phytoplasma that infected any annual plant like a tomato or cosmos, however, would have died with the plant at the first hard frost. Very few aster leaf hoppers overwinter in Minnesota as eggs and these do not carry the aster yellows phytoplasma. In addition, surveys indicate that lower than average numbers of aster leafhoppers migrated into Minnesota in 2013. Gardeners should continue to watch for symptoms of aster yellows and remove any infected plants.

Karl Foord - Extension Educator, Horticulture


Click on the link to see the video with host Dr. Mary Meyer, Professor of Horticulture

Karl Foord

Photo 1: Garden Glow Dogwood (Cornus hessei 'Garden Glow')


Garden Glow Dogwood




Karl Foord


Photo 2: Bracken Fern (Pteridium aquilinum)



Bracken Fern




Karl Foord


Photo 3: Lady's Mantle (Alchemilla mollis)



Lady's Mantle




Karl Foord


Photo 4: Hosta 'Glory'


Hosta 'Glory'

Karl Foord

Photo 5: Bugbane, Black Snakeroot (Actaea racemosa)


Bugbane

Karl Foord

Photo 6: Purple Fringed Loosestrife Lysimachia ciliata

Purple Fringed Loosestrife

Editors note: These videos were filmed in 2012

Karl Foord - Extension Educator, Horticulture


Click on the link to see the video with host Dr. Mary Meyer, Professor of Horticulture

Karl Foord

Photo 1: Russian Sage (Perovskia atriplicifolia)

Russian Sage

Karl Foord

Photo 2: Ingwersen's Variety Geranium (Geranium macrorrhizum 'Ingwersen's Variety')

Ingwersen's Variety Geranium

Karl Foord

Photo 3: Adam's needle (Yucca filamentosa)


Adam's Needle (Yucca filamentosa)




Karl Foord


Photo 4: Giant Fleece Flower (Persicaria polymorpha)



Giant Fleece Flower

Karl Foord

Photo 5: Rosa 'Summer Waltz')

Rosa 'Summer Waltz'

Giant Onion Rose Mallow Combination




Karl Foord


Photo 6: Rose Mallow (Hibiscus 'Blue River II')



Harebell Campanula

Karl Foord

Photo 7: Harebell Campanula (Campanula rotundifolia)

Editors note: These videos were filmed in 2012

Redheaded Flea Beetles in the Landscape

Jeffrey Hahn, Extension Entomologist

Linda Treeful

Photo 1: Redheaded flea beetle on turlehead (Chelone). Note the irregular brown patches of feeding damage on the leaves.

The redheaded flea beetle, Systena frontalis, is a native insect to Minnesota. It is small, about 1/8 to a ¼ inch long. It has a shiny black body with an orangish red head and moderate length antennae. Like other flea beetles, its hind legs are enlarged and made for jumping.

Redheaded flea beetles feed on a wide variety of plants, especially agricultural crops such as corn, soybeans, cabbage, and alfalfa as well as many weeds. They are now being found in the landscape and nurseries for seemingly the first time where they have been reported feeding on hydrangea, viburnum, and other shrubs as well as many perennials.

Adults typically hatch in July and August and are active on plants until September.
Their feeding can cause small holes which can create a skeletonized appearance in the leaves. In plants with thicker leaves, they remove irregular patches of leaf tissue which eventually turns brown. We have received reports of these beetles in the landscape in Hennepin, Clay, and Carlton counties although they are undoubtedly in other sites in the state.

These flea beetles typically cause little damage to plants. The injury people see on their shrubs and perennials are generally going to only affect the appearance of them. If it does become desirable to treat redheaded flea beetles, they should be easily managed with most residual insecticides.

Redheaded flea beetles have been particularly abundant this year. It is unclear whether this is an emerging landscape problem or a temporary blip. We would be interested to hear any reports of this insect attacking landscape plants. If you encounter redheaded flea beetles, send an e-mail to the author (hahnx002@umn.edu) and report what plants it is attacking and the location. Also include a picture if possible.

Genista Broom Moths Return to Minnesota

Jeffrey Hahn, Extension Entomologist

Pam Hartley

Photo 1: Genista broom moth caterpillars on false indigo.

Genista broom moths, Uresiphita reversalis, were found last year for apparently the first time in Minnesota. They fed almost exclusively on false indigo (Baptisia) here. Other plants that they are known to attack include lupines and honeysuckle (Lonicera spp.)

It was thought that their appearance here the result of migrant moths moving into Minnesota, probably with the help of storm fronts. The question was whether they would survive winters in Minnesota and would we see them again next year. It is not clear whether any of them survived our winter but it is clear that they are in Minnesota again in 2013 as reports have been coming in since mid-July. Most of the sightings have been in the Twin Cities area, but this caterpillar has also been spotted west of Minneapolis in McLeod County. Most of the sightings have been on false indigo with one report on lupine.

Interestingly, genista broom moth caterpillars have generally have not been reported in Iowa, although one home gardener spotted them in east central Iowa. They have not been reported in Wisconsin to date.

If you find these caterpillars in your garden and they are about one inch long, you can ignore them as they are essentially done with their feeding. If they are smaller, you have a few options. Probably the easiest thing you can do is to handpick them. It they are numerous, consider a low impact insecticide, such as insecticidal soap, spinosad, or Bacillus thuringiensis.

If you discover this caterpillar in your garden, especially in Minnesota, please contact the author (hahnx002@umn.edu) and report it. We are trying to determine where these insects have been found and whether they return the following summer.

Karl Foord - Extension Educator, Horticulture

Karl Foord

Photo 1: Flower garden for pollinators

Karl Foord

Photo 2: Great black wasp (Sphex pensylvanicus)

Karl Foord

Photo 3: Great black wasp (Sphex pensylvanicus) on left

Karl Foord

Photo 4: Great black wasp (Sphex pensylvanicus) and golden digger wasp (Sphex ichneumoneus) on Culver's Root (Veronicastrum virginicum)


I am not sure what I expected when I created this pollinator garden (photo 1), but I have certainly gotten a whole new perspective on what happens in a flower garden. I have encountered so many different species that I will create a series of pollinator garden observations. I will begin with wasps and follow up with many types of flies and bees.

The garden has been continually patrolled by a great black wasp (Sphex pensylvanicus). This wasp is perceived as a black streak that weaves its way around the different plants in the garden searching for prey (photos 2 & 3). It only rarely lands to fuel up on nectar at a Culver's Root plant (Veronicastrum virginicum) seen here with a golden digger wasp (Sphex ichneumoneus) (photo 4). It sometimes hassles other residents. I have seen it touch the back of bumblebees who fly in response but are not harmed. It had an encounter with a hummingbird but both went their separate ways.




Karl Foord


Photo 5: bald-faced hornet (Dolichovespula maculata)



I encountered a bald-faced hornet (Dolichovespula maculata) gathering nectar on Summer Beauty Onion (Allium lusitanicum 'Summer Beauty'). It looked to have enough hairs to actually be accomplishing some transfer of pollen.




Karl Foord


Photo 6: Thick-headed Fly (family Conopidae)



Another interesting character was this Thick-headed Fly (family Conopidae) whose thread-waist mimics that of the Sphecid wasps. The thick-headed fly was on Hoary Vervain (Verbena stricta).

Karl Foord

Photo 7: Cuckoo Wasp (Family Chrysididae)

Lastly we have a iridescent well armored Cuckoo wasp (Family Chrysididae) (photo 7). This wasp is parasitic on other wasps, laying its eggs in the already provisioned nests of other wasps.




Karl Foord


Photo 7: Cuckoo Wasp (Family Chrysididae)


A well camouflaged female Goldenrod Crab Spider (Misumena vatia ) was quite tentative around this customer. I have seen crab spiders with captured flower flies and butterflies, but this wasp may have been too well armored to warrant an attack.

Karl Foord

Photo 8: Cuckoo Wasp (Family Chrysididae) and Goldenrod Crab Spider (Misumena vatia)

The other interesting thing is that I am sure there are at least 10 other species of wasps in the garden that I have observed but not yet identified. To be continued...

Editor's note: The primary reference for this article was Jeff Hahn's book Insects of the North Woods. The spider was identified through Larry Weber's book Spiders of the North Woods. Thanks to both of these authors.

Grape pelidnota

Jeffrey Hahn, Extension Entomologist

Grape Pelidnota

Jeff Hahn

Photo 1: Grape pelidnota-- a big scarab beetle

A conspicuous insect has been showing up this summer around people's gardens and homes. A grape pelidnota, Pelidnota punctata, is a type of scarab beetle that looks like a big June beetle. Also known as grapevine beetle, it is a good sized insect measuring about one inch long. It is a rusty orange color with six black spots on its body (two on its thorax and four on its wing covers).

Grape pelidnotas can be found throughout the late spring and summer. Like their name suggests, the adults feed on grapes, although they typically do not cause much damage (just handpick them if they become numerous). The larvae are associated with rotting hardwood tree logs and stumps. The adults are attracted to lights so you can find one around your home even if you don't have grapes. Although they might look imposing, grape pelidnotas are harmless to people and pets. They are just a curiosity and can be ignored.

Karl Foord - Extension Educator, Horticulture


Click on the link to see the video with host Dr. Mary Meyer, Professor of Horticulture

Karl Foord

Photo 1: Gooseneck Loosestrife ( Lysimachia clethroides)


Gooseneck Loosestrife

Karl Foord

Photo 2: Variegated Japanese Knotweed (Fallopia japonica 'Variegata'.)


Variegated Japanese Knotweed




Karl Foord


Photo 3: Goatsbeard (Aruncus dioicus)



Goatsbeard




Karl Foord


Photo 4a: Jack-in-the-Pulpit (Arisaema triphyllum)


Karl Foord

Photo 4b: Jack-in-the-Pulpit (Arisaema triphyllum)

Jack-in-the-Pulpit

Karl Foord

Photo 5: Siberian Bugloss (Brunnera macrophylla)


Siberian Bugloss Brunnera

Dry Shade

Editors note: These videos were filmed in 2012

Karl Foord - Extension Educator, Horticulture


Click on the link to see the video with host Dr. Mary Meyer, Professor of Horticulture

Karl Foord

Photo 1: Flowering Onion (Allium spp.)

Flowering Onion




Karl Foord


Photo 2: Our host Dr. Mary Meyer showing the William Baffin Rose


William Baffin Climbing Rose

Karl Foord

Photo 3: May Night Salvia (Salvia x sylvestris 'Mainacht'

May Night Salvia

Karl Foord

Photo 4: Gas Plant (Dictamnus albus)


Gas Plant

Karl Foord

Photo 5: Ozark Sundrops (Oenothera macrocarpa)

Ozark Sundrops Oenothera

Little Rocket Ligularia

Karl Foord

Photo 6: Little Rocket Ligularia (Ligularia stenocephala 'Little Rocket')

Lamb's Ear

Karl Foord

Photo 7: Lamb's Ear (Stachys byzantina)

Editors note: These videos were filmed in 2012

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