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Showing posts from May, 2011

Look for Rust Fungi on Trees

Michelle Grabowski, UMN Extension Educator

A group of pathogenic fungi known as rusts can be easily seen and identified on evergreen trees this time of year. Mild temperatures and spring rains cause the rust fungi to produce brightly colored orange or yellow spore producing structures on infected branches.

Some diseases caused by rust fungi are minor problems and only affect the aesthetics of the tree. Others can be fatal to the tree if proper action is not taken in time. It is therefore critical for gardeners to understand how to identify the rust fungi that they are seeing on their plants.

The following rusts may be catching your eye.

Photo 1: Cedar Apple Rust Gall with gelatinous orange spore producing structures M. Grabowski, UMN Extension.
Cedar Apple Rust

Cedar Apple Rust (CAR) is caused by the rust fungus Gymnosporangium juniperi-virginianae. This fungus infects several species of juniper including eastern red cedar (Juniperus virginiana) Chinese juniper (J. chinensis), creeping…

Pine sawfly larvae are out and about - Check your Scotts, Red, Mugo, and Austrian Pines

Photo 1, Karl Foord, UMN Extension Educator.

Keep an eye out for tent caterpillars and Pine sawfly larvae. Look for shriveled and missing needles on pine branches just below the newly forming candles (Photo 1). The larvae are gregarious and form in numbers on these sections of the plant. They are quite voracious and can strip a tree quickly (Photo 2). It is best to wash them off the plant with water rather than to use an insecticide. See Jeff Hahn's article for a more detailed account of pine sawfly.

Pine sawfly larvae exhibit some fascinating forms of defensive behavior. Colonies of larvae will rear their heads in unison when disturbed. This behavior may serve to startle potential predators (

Photo 2, Karl Foord.

Pine sawfly larvae also collect pine resin in a special gut compartment as they feed. When attacked by a predator, the larva will regurgitate a droplet of pine resin and try to dab it on the predator. Ants and other pre…

Solitary Bees With a Twist

Jeffrey Hahn, Asst. Extension Entomologist

Photo 1: Andrenid bee. Jeff Hahn.

Andrenid bees, especially Andrena spp., are common insects that are sometimes seen in yards and gardens in spring. They are small to medium sized insects, about 1/4 - ½ inch long. They are hairy, dark-colored insects, often with a thick mat of yellow hairs on their thorax.

They typically overwinter as pupae and emerge as adults as soon as the weather becomes warm, living for about a month. Andrenid bees nest in the ground, preferring sunny, dry sites with sparse grass or few plants. They create cylindrical tunnels where they spend essentially their entire life preparing these nests for their young. They provision them with pollen balls on which the larvae feed during summer.

Unlike honey bees and bumble bees, which are social insects living in colonies, andrenid bees are solitary insects that live by themselves. They are responsible for all of the work that is required to maintain the nest and prov…

Calendar: June 1, 2011

Damage on Chocolate Mint Mentha x piperita f. citrata 'Chocolate'Karl Foord.
Four-lined plant bug nymphs love mint, as shown on the photo to the right. Their feeding causes small, necrotic spots. The damage can look a little different on different plants, but is similar enough to recognize. Thanks to Jeff Hahn for identification of the nymph.Check flowering perennials closely for signs of four-lined plant bug feeding-- small brown circular depressions on the leaves. This usually doesn't injure the plants seriously, but it does make them less attractive and sometimes the bugs can truly overrun the plant. It's best to tolerate four-lined plant bugs whenever possible, but if you decide to control them, you must spray soon after you first notice feeding damage. Check out the UMN Extension Garden page for more information.Assess the performance of your spring-flowering bulbs. Lift and discard any that failed to bloom well; they won't improve. Fertilize the others, and a…

EAB Awareness Week

Jeffrey Hahn, Asst. Extension Entomologist
With a stroke of his pen, Governor Mark Dayton signed a proclamation officially declaring May 22 - 28 as EAB (Emerald Ash Borer) Week in Minnesota. This is a good opportunity to remind people that EAB is still a serious pest that threatens our state's nearly 1 billion ash trees. That week also corresponds with the official start to camping season as people travel for the Memorial Day weekend.

Photo 1: Adult emerald ash borer. Jeff Hahn.

The theme for EAB Awareness Week is 'Keep our trees safe. Use MDA (Minnesota Department of Agriculture) certified or local firewood.' This is such a critical message for people to understand that the one of the most important methods for EAB to be transported into areas that are uninfested is through firewood. That is why people are strongly encouraged to leave their firewood at home and buy from local, approved firewood vendors.

Currently EAB is known only in Ramsey, Hennepin, and Houston cou…

Espalier - An Art Based on Science

Karl Foord, UMN Extension Educator

Monet's garden. Karl Foord, UMN Extension Educator.


Espalier is a plant shaping/pruning method where plants are grown in a single plane limiting their height and width to a defined area. The area is usually defined by a permanent framework which stabilizes the plant. The espalier is developed and maintained by pruning techniques of which timing is a critical part, for a pruning cut made in early spring will likely have different results than one made in midsummer.

Exhibit 2: Espaliered apples as a low-growing fence.
Espalier takes on a number of high profile roles in the landscape. It can be the focal point of the landscape design or take on lesser roles as privacy screens or backdrops. It can function as a key plant softening the appearance of walls or act as an accent or specimen plant. An accent plant has year around interest like most evergreens. A specimen plant has seasons of interest such as flowering, fruiting or attractive …

Black Root Rot in Flowering Annuals

Michelle Grabowski, UMN Extension Educator

Photo 1: Petunias infected with black root rot T. Burnes, UMN Dept. of Plant Pathology.
With the weather warming up but the risk of frost not entirely past, many annual bedding plants are spending their days in pots. Gardeners are working to keep these plants healthy until they reach their permanent home in a hanging basket or in the front garden bed. Poor growth and yellowing leaves on these plants may be a sign of a root rot problem.

Black root rot, caused by the fungus Thielaviopsis basicola, has recently been identified in flowering annuals in Minnesota. Thielaviopsis can result in severe root rot in cool temperatures; 55-62F being ideal. Above ground symptoms are often mistaken for nutrient deficiency. Plants are slow growing or stunted. Leaves are yellow and leaf veins may remain green. The symptoms that give this disease its name are to be found below ground. Dark sunken black lesions occur on roots of all sizes. Under the microscope …

Protect Yourself From Tick Diseases

Jeffrey Hahn, Asst. Extension Entomologist

The Minnesota Department of Health (MDH) recently issued a news release detailing the marked increase in the number of tick-borne diseases in 2010. MDH tallied 2,069 cases of Lyme disease, Human anaplasmosis and babesiosis from last year. While the number of Lyme disease cases only went up a little, Human anaplasmosis cases more than doubled and instances of babesiosis were nearly twice as much compared to 2009.

Photo 1: Adult female blacklegged tick. Jeff Hahn.

Blacklegged ticks (formerly known as deer ticks) is the species responsible for transmitting these diseases. The highest risk areas in Minnesota are in the eastern, central, and southeast areas of the state. Symptoms are variable. When dealing with Lyme disease, many cases (but not all) exhibit a red, circular, bull's-eye rash. Other disease symptoms can range from no reaction to arthritis, neuropathy, headaches, fevers, chills, and muscle aches, joint swelling, cardiac and…

Lawn watering practices that encourage healthy lawns and help protect water resources

Bob Mugaas, UMN Extension Educator, and Dr. Brian Horgan, Turfgrass Management, UMN Department of Horticultural Science

Photo 1: Proper watering benefits all landscape plants, especially lawns. Bob Mugaas.

While water is essential for all plant growth, it is not always uniformly available or distributed when and where the plant needs it. Therefore, supplemental water is often needed to sustain and support healthy plant growth whether it's vegetable plants, annual flowers, trees and shrubs or lawn grasses. Picture 1. For most of us, that means getting out sprinklers and hoses and watering on occasion. There are also automated systems available to aid in the distribution and convenience of supplying supplemental water to lawns. Following are some watering practices beneficial to lawns that can help minimize unintended, negative environmental impacts.

Water friendly lawn care practices anyone can implement

During the hot and dry summer months, lawns will need about an inch of wat…

A new kind of Tulipomania is alive and well at the Landscape Arboretum

Karl Foord, UMN Extension Educator.

If you have the opportunity and the interest, check out the tulip displays at the Minnesota Landscape Arboretum in the near future while they are still at peak; for lack of a word "spectacular" (Exhibit # 1).

I was reading Michael Pollan's book, "The Botany of Desire" and came upon the chapter on tulips and his description of 'tulipmania'. You may remember the history of this period but it is worth reviewing.

In Holland a great furor about tulips whose petals were colored with dramatic streaks and stripes began in 1593. It reached a high point in 1637 when a tulip bulb of the variety 'Semper Augustus' sold for 10,000 florins (exhibit # 2). At this time such a sum of money would have purchased a house, including gardens and coach house, in a very desirable location near the canal in central Amsterdam. This was also the year that the bottom fell out of the tulip bulb market and many speculators were bankrup…

Garden Calendar: May 15, 2011

Fritillaria imperialis
'Rubra maxima' Karl Foord.

Fritillaria imperialis Crown Imperial. Karl Foord.

We are at least two weeks behind an "average" spring. Last year at this time we had experienced a Mother's Day (May 9, 2010) frost which killed many strawberry and apple flowers. This year as of May 13th the apples are in red bud stage and will likely start flowering next week. I have not seen a strawberry flower.

New tree id app designed by the Smithsonian

This new app is a great tool for identifying trees, and it has some citizen scientist applications as well. The location of the tree and its identity are recorded automatically. See more at the Smithsonian website!

It is currently only available to iPhones but will be released for android later this summer. And it's free!

Yard and Garden News Editor: Karl Foord
Technical Editor: Bridget Barton

What Is That Insect?

Jeffrey Hahn, Asst. Extension Entomologist

An interesting insect, found under unusual circumstances, was reported recently. A gentleman had a large dead branch pruned out of his maple in February. It had rotted in the center and was a hazard that needed to be removed. He cut the limb into smaller pieces and stacked them in April. He noticed in one branch section where the wood had rotted an accumulation of mud.

Photo 1: Rat-tailed maggots.
Kyle Jensen.
He removed the mud and uncovered several pinkish larvae with long 'tails'. They were legless with no obvious head. These insect larvae are rat-tailed maggots, Eristalis spp. The most commonly encountered species is Eristalis tenax. The body of a mature rat-tailed maggot is about 3/4 inch long with the telescopic breathing tube (the 'tail') as long as two inches. This insect belongs to the family Syrphidae which are commonly called flower flies or hover flies because adults are typically found around flowers and a…

Zinnias for Your Yard and Garden

Photo 1: Benary's Giant Wine
Robin Trott, UMN Extension Educator

Last summer was the first year I grew zinnias in any quantity. Spaniards who first saw them growing in Mexico thought zinnias were so unattractive they called them "mal de ojos", or "sickness of the eyes"; and until last summer, I tended to agree. I thought zinnias were large, gaudy flowers that didn't even have the redeeming quality of a pleasant fragrance; and so I never grew them in my home garden. Boy, was I wrong!

Last summer I grew many tall zinnia varieties to be used as cut flowers. Benary's giants were spectacular, and the peppermint stick varieties were something else. It's no wonder that the National Garden Bureau has declared 2011 the "Year of the Zinnia."

One of the reasons for the booming popularity of the zinnia is its diversity. Zinnias have a variety of flower forms--they may be single, semi-double, or double. Single Zinnias, Zinnia angustifolia, have one…

Understanding and Using Home Lawn Fertilizers - Part III: Returning to phosphorus and potassium.

Bob Mugaas, UMN Extension Educator

Photo 1: Steps for properly taking a soil test.
Karen Vidmar, University of Minnesota.

Over the last couple of articles we have explored how to better understand the sometimes bewildering array of lawn fertilizers available and make appropriate choices for one's own lawn as well as the large and diverse role that the nutrient nitrogen plays in the life of lawn grasses. Part III, the final section of this three-part series, will turn attention back to the nutrients phosphorus (P) and potassium (K) and the important roles they play in turfgrass health. Since determining the amount of P and K in a container of lawn fertilizer was thoroughly discussed in the first article of this series, this last article will focus on the importance of P in K in turfgrass health and their application as a component of lawn fertilizers. Before beginning, remember that the best way to determine the amount of P and K in your soil is to have a reliable soil test don…