Skip to main content


Showing posts from July, 2012

July 15, 2012

Aster Yellows common in Cone Flowers Throughout Minnesota

Michelle Grabowski, UMN Extension Educator

M. Grabowski, UMN Extension
Photo 1: Purple cone flowers on a plant infected with aster yellows

Many gardeners are noticing that their cone flowers (Echinacea spp.) are not so purple this year. In fact many flowers are partially to completely green and several have odd green growths sticking up from the center of the the blossom. These are symptoms of the disease aster yellows.

Aster yellows is caused by a tiny bacteria - like organism known as a phytoplasma. Phytoplasmas live with the phloem (nutrient conducting vascular system) of plants. The aster yellows group of phytoplasmas can infect over 60 families of plants including many common garden perennials, vegetables and weeds. Although many gardeners are noticing disease symptoms on coneflowers, infection of other plants such as cosmos, golden rod and carrot have also been reported.

Leaves of plants infected with aster yellows are often discolored yellow to red. The phytoplasma affects norm…

Welcome to Our New Turfgrass Extension Educator

Kathy Zuzek - Extension Educator, Horticulture

Extension would like to welcome Sam Bauer back to the University of Minnesota as a new Horticulture Extension Educator in EFANS. Sam will be starting July 16, 2012 and will be housed at the Regional Extension Office in Andover. Sam's primary responsibilities in horticulture are with consumer turfgrass. He will work closely with other Horticulture Extension Educators and with faculty in the Department of Horticultural Science. Sam received his B.S. and M.S. from the University of Minnesota in 2005 and 2011 respectively and is well versed on turfgrass issues facing the consumer. He brings with him tremendous international turfgrass experience and a solid understanding of how to connect with the public through social media. Sam can be reached at or (763) 767-3518.

Variegated Cutworm Damage

Jeffrey Hahn, Asst. Extension Entomologist

Jeff Hahn
Photo 1: Variegated cutworm damage on hosta
A large flight of variegated cutworm moths moved through Minnesota as well as Wisconsin this spring. This was particularly noticeable when clusters of eggs were found on many buildings and other structures during May (see June 1, 2012 Yard and Garden News)

The result of this activity is now being felt in home gardens as many different herbaceous plants that are being damaged by their feeding. Unlike subterranean cutworms that many gardeners are familiar with, variegated cutworms are a type of climbing cutworm that will feed on the foliage of plants. They typically chew irregular holes between the veins on the leaves. They have also been known to bore into flower buds. Be careful not to confuse variegated cutworm feeding with slug damage which can look similar. Slug feeding usually results in more ragged, irregular holes but to be sure, you may have to catch the culprits in the act.


Watch Out For Wasp Nests

Jeffrey Hahn, Asst. Extension Entomologist

Now is a good time to take a close look for wasp nests around your home. They are getting large enough to be noticed but have not reached their peak size yet. Wasps can nest in a variety of locations. Some species commonly nest under eaves of homes, the branches of trees and shrubs, and similar open, exposed areas. They also commonly nest in the ground, especially in old rodent burrows, as well as wall voids, attics, and other hidden sites. If you see any kind of persistent activity of wasps in a particular location, take a closer look to see if there is a nest involved.

Jeff Hahn
Photo 1: Wasp nests can be found in the most unexpected places
One wasp, the European paper wasp, is interesting because of its ability to construct small nests in many different, unusual sites. Just in the author's backyard, they have been found nesting in the tail pipe of a unused van and inside an unused bird feeder. Paper wasps typically nest on the undersid…

Quince Rust on Hawthorn Results in Strange Looking Fruit

Michelle Grabowski, UMN Extension

M.Grabowski, UMN Extension
Photo 1: Quince rust on a hawthorn fruit

Quince rust, caused by Gymnosporangium clavipes, can infect over 480 species of plants within the Rosaceae family. This includes serviceberry (Amelanchier spp.), hawthorn (Crataegus spp.), chokeberry (Aronia sp.), mountain ash (Sorbus spp.), apple and crabapple (Malus spp.). Quince rust frequently infects fruit and petioles, causing them to be swollen and deformed. At this time of year, the fungus produces short white cylindrical spore producing structures all over infected fruit. These spore producing structures open up to release bright orange powdery spores that give rust fungi their name. Infected fruit will die. Although odd looking, these infections are not harmful to the overall health of the plant.

Flowering Plant Video Library - Prairie Plants II

Karl Foord - Extension Educator, Horticulture

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

Purple Prairie Clover (Dalea purpurea)

Karl Foord
Photo 1: Purple Prairie Clover (Dalea purpurea)

False Indigo (Baptisia australis)

Karl Foord
Photo 2: False Indigo (Baptisia australis)

Prairie Dock (Silphium terebinthinaceum)

Karl Foord
Photo 3: Prairie Dock (Silphium terebinthinaceum)

Cup Plant (Silphium perfoliatum)

Karl Foord
Photo 4: Cup Plant (Silphium perfoliatum)

Harebell Campanula (Campanula rotundifolia)

Karl Foord
Photo 5: Harebell Campanula (Campanula rotundifolia)

Native Prairie Lily (Lilium philadelphicum)

Karl Foord
Photo 6: Native Prairie Lily (Lilium philadelphicum)

Golden Alexanders (Zizia aurea)

Karl Foord
Photo 7: Golden Alexanders (Zizia aurea)

July 1, 2012

Leafcurl Ash Aphids on Ash

Jeffrey Hahn, Asst. Extension Entomologist

This June has seen a lot of activity by leafcurl ash aphids, a type of woolly aphid, not only in the Twin Cities but also in a number of other areas in Greater Minnesota. Like other aphids, leafcurl ash aphids use piercing - sucking mouthparts to feed on the sap in the leaves. This feeding causes leaves to become tightly curled, puckered, and distorted. To verify leafcurl ash aphids, unroll the leaves. The aphids are a light green and no more than 1/8 inch long. They produce a conspicuous white waxy material that covers the aphids as well as the leaves.

Kim Sullivan
Photo 1: Leafcurl ash aphid. Note the curled leaf and the white waxy material

These aphids also produce a lot of honeydew. Honeydew is a sticky waste material because the aphids are not able to digest all of the sugars in the sap. Any objects under a leafcurl ash aphid infested tree can get coated with this substance. Later you might find sooty mold, a black fungus deve…

Tomato Leaf Spot Season Begins

Michelle Grabowski, UMN Extension Educator

M.Grabowski, UMN Extension
Photo 1: Leaf spot diseases starting on the lower leaves of a tomato plant

Warm wet weather throughout Minnesota has provided excellent conditions for tomato leaf spot pathogens to grow and spread. The first leaf spots of many tomato diseases have recently been observed.

Both fungal and bacterial leaf spot diseases are commonly found on tomatoes in Minnesota. Septoria Leaf Spot, Early Blight, and Bacterial Spot are all common problems on garden tomatoes. All of these diseases overwinter on infected plant debris in the soil. Rain or irrigation can splash spores or bacteria up onto the lower leaves of the plant to start new infections.

If you are growing tomatoes this year, take the time now to examine the lower leaves of your plants. Look for black to brown spots on the leaves closest to the ground. For help identifying which disease is affecting your plant visit the 'What's wrong with my plant?' online d…

Amazing Leaf-Cutter Bees

Karl Foord - Extension Educator, Horticulture

I was walking through the Horticulture Display Garden at the University of Minnesota St. Paul Campus. A bee landed on the ground and disappeared. I got my camera but couldn't find the hole it had disappeared into, so I waited. In a few minutes the bee returned with a bit of leaf rolled under its abdomen and again disappeared down the now somewhat visible hole.

This was no leisurely entrance and exit from the hole. The time from seeing the bee approach the hole to disappearance was less than one second. It took less time for the bee to show at the top of the hole and exit. The bee exited headfirst so it had had enough room in the hole to turn around.

The bees that nest in this way are aptly named Leafcutter bees and are in the genus Megachile (Photo 1).

Karl Foord
Photo 1: Leafcutter bee (Megachile spp.) on Sea Holly (Eryngium planum)

They are identified by the hair on the bottom of their abdomen which traps pollen. They do not have a …

Hawthorn Mealybug: An Interesting Insect in the Landscape

Jeffrey Hahn, Asst. Extension Entomologist

Hawthorn mealybug, Phenacoccus dearnessi, has been found infesting several hawthorns in Minneapolis. This insect is globular and red, although it will appear to be white as it is covered with a white waxy material. In addition to hawthorn, it can also attack mountain ash (an infested mountain ash was found adjacent to the hawthorns), cotoneaster, juneberry (amelanchier), and other plants in the rose family.

This is not a common insect in Minnesota. In fact in Minnesota the best place to find mealybugs is on greenhouse and house plants and not landscapes. Even our neighbors in Wisconsin and Iowa have not seen the hawthorn mealybug (so far). It is, however, found in northeast Illinois.

Whitney Cranshaw, Colorado State University,
Photo 1: Hawthorn mealybug

This insect colonizes the bark of twigs and small branches using its piercing sucking mouthparts to feed on the sap. Hawthorn mealybugs also produce a lot of honeydew, …

Blow Flies and Flesh Flies

Jeffrey Hahn, Asst. Extension Entomologist

Some people have discovered the sudden appearance of medium sized flies in their homes. Blow flies are iridescent green, blue, or coppery colored flies while flesh flies have dark colored bodies with three black stripes on their thorax and a checkerboard pattern on their abdomen. Both types of flies lay their eggs on dead animals and decaying garbage. The larvae are smooth, cream-colored, legless maggots that are carrot-shaped with the narrowest end by the head. When fully grown, they are about 3/4 inch long.

Jeff Hahn
Photo 1: Blow flies on animal remains

When a dead animal becomes trapped inside a home, e.g. inside a ceiling or wall void, and dies, it is not uncommon for it to attract these flies which lay eggs on the corpse. Eventually they turn into adult flies which can emerge into the home. It is also possible to see the maggots inside a home. As mature maggots wander away from their food source to less crowded sites to pupate, t…

The Eyes Have It

Jeffrey Hahn, Asst. Extension Entomologist

Jeff Hahn
Photo 1: Eyed click beetle

During June, some people encountered eyed click beetles, Alaus oculatus, an interesting and conspicuous looking insect. An eyed click beetle is large, about 1 - 1 3/4 inch long. The wing covers are black mottled with small whitish patches. What are immediately noticeable are the two eyespots on its prothorax (the area behind its head) which are velvety black surrounded by a whitish ring. Eyed click beetles are associated with decaying logs and stumps and are found in open wooded areas. Watch for and enjoy the adults during spring. This insect is harmless and just a curiosity.

Black Rot on Crucifers

Michelle Grabowski, UMN Extension Educator

M. Grabowski, UMN Extension
Photo 1: Black Rot Lesion on a Broccoli Leaf

A bacterial disease of crucifers (cabbage, broccoli, cauliflower, radishes, Brussels sprouts and more) called black rot caused severe damage to many gardeners last year and has been found again in Minnesota this summer. Black rot is caused by the bacteria Xanthomonas campestris pv. campestris. This pathogen often enters a garden on contaminated seed. It can also survive on infected weeds like wild mustard and pepper weed or in plant debris from previous years infected crop.

Black rot can be recognized by the v shaped lesions that form on infected leaves. The tip of the V points towards the mid rib of the leaf. The center of the v is often dead brown tissue which is surrounded by a yellow halo. As the disease progresses, leaf veins turn black within the lesion. The infection can move into the plants vascular system and result in wilt and soft rot.

Black rot enters the leaf t…

Flowering Plant Video Library - Prairie Plants I

Karl Foord - Extension Educator, Horticulture

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

Common Milkweed (Asclepias syriaca)

Karl Foord
Photo 1: Common Milkweed (Asclepias syriaca)

Foxglove Beardtongue (Penstemon digitalis)

Karl Foord
Photo 2: Foxglove Beardtongue (Penstemon digitalis)

Prairie Phlox (Phlox pilosa)

Karl Foord
Photo 3: Prairie Phlox (Phlox pilosa)

White Wild Indigo (Baptisia alba)

Karl Foord
Photo 4: White Wild Indigo (Baptisia alba)

Common Ox-eye (Heliopsis helianthoides)

Karl Foord
Photo 5: Common Ox-eye (Heliopsis helianthoides)

Butterfly Milkweed (Asclepias tuberosa)

Karl Foord
Photo 6: Butterfly Weed (Asclepias tuberosa)