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Showing posts from September, 2011

The Appeal of Integrated Pest Management (IPM)

Karl Foord, UMN Extension Educator


Green lacewing larvae searching for prey on a yarrow flower.
The goal of IPM is to prevent unacceptable levels of pest damage through the use of pest biology and environmental information. It seeks a solution that poses the least possible risk to people and the environment.

The great appeal of IPM is the understanding of the biological systems at play in the garden and the degree one needs to understand them in order to effectively use IPM strategies. This requires a certain knowledge and skill set. One needs to be able to identify the key insect and disease pests and the types of damage they inflict. One needs to understand the biology of these key pests and how climate influences their behavior. It is also important to understand the natural balances that exist in your garden ecology and to be able to identify beneficial organisms that are a part of that balance. The last item is to understand the use of various chemicals and their effects both di…

Fruit Flies

Jeffrey Hahn, Asst. Extension Entomologist


Jeff Hahn
Photo 1: Fruit fly

Fruit flies are particularly common in homes during fall. These flies, Drosophila spp., are about 1/8th inch long with a tannish body, and a dark-colored abdomen. An easy way to identify fruit flies is by their bright red eyes. However, their eyes do appear darker after they are dead and may not be as distinctive. Be careful, not every small-sized fly you encounter is automatically a fruit fly. Moth flies, phorid flies (also called humpbacked flies), and fungus gnats can also be common in homes. It is important to know which fly you are seeing because control will vary depending on which fly is present. If you have any doubts as to which fly is in your home, have an expert identify it for you.

Fruit flies can potentially be carried into homes in fruits and vegetables or they could fly in from the outside. Once in homes, they are attracted to fermenting and souring smells, e.g. around garbage containers and…

Clean up Fall Leaves and Clean Up Leaf Spot Diseases

Michelle Grabowski, UMN Extension Educator


M.Grabowski, UMN Extension
Photo 1: Fallen Leaves Infected with Apple Scab

As the weather turns cold, disease management in the yard and garden shifts from thinking about protecting plants this year to working to reduce disease problems next year. Many leaf spot diseases of shade trees overwinter in the fallen leaves below the tree. Apple scab on crab apple and tar spot on maple are two examples. When warm wet spring weather returns, these leaf spotting fungi become active again and produce spores that are then blown or splashed onto new emerging leaves. This starts the disease cycle all over again.

Gardeners can help reduce the amount of leaf spot fungi surviving from one season to the next by raking up and removing leaves from underneath trees that experienced a leaf spot problem this year. Leaves should be properly disposed of in a backyard compost or at a municipal or commercial compost facility. The compost needs to heat up in order to k…

Pruning Trees to Avoid "Disasters"

Karl Foord, UMN Extension Educator

USDA Forest Service Figure 1: Crown thinning
Karl Foord, UMN Extension Educator
USDA Forest Service Figure 2: Crown raising
Tree planted in 1997.
Before
After I have Autumn Blaze maple trees that produce great fall color and grow very quickly. In the tree trade they are known as "disasters" because they produce a very dense canopy that is subject to limb breakage in ice storms and uprooting in high winds. To avoid my trees becoming disasters I have pruned them to the point where I was pretty high up in the tree and getting in precarious positions. It was time to get an arborist. I took pictures of the trees before pruning and after pruning to see the difference and then looked on line for verification.

The arborist pursued two strategies, crown thinning (Figure 1) and crown raising (Figure 2) both taken from the USDA Forest Service publication, "How to Prune Trees".
The before and after pictures show that some lower limbs were r…

Calendar: October 1

Julie Weisenhorn
Acer saccharum (Sugar Maple)
Leave a couple inches of stem attached when you pick pumpkins. Since they have almost no frost tolerance, they must be harvested or protected if frost is forecast. Pumpkins ripen best on the vine, but may turn orange in storage if not completely ripe when picked. Wipe them clean with a damp, slightly soapy cloth, then put them in a warm sunny spot for a week or two to cure them. Store in a cool dark place.

Continue to mow the lawn as needed, and rake fallen leaves so grass doesn't mat down and encourage snow mold development. Or, if the leaves aren't too deep, run a power mower over them several times. This chips them into little pieces that filter harmlessly through the grass into the soil, recycling a small amount of nutrients as they break down. Otherwise, use the leaves to protect bulbs and flowering perennials, or compost them.

As the gardening season winds down, so does the Yard and Garden News. Beginning this month, we will …

Fall Webworm

Jeffrey Hahn, Asst. Extension Entomologist


Jeff Hahn
Photo 1: Fall webworm feeding on black walnut
Fall webworm, Hyphantria cunea, is a web building moth that is common from mid to late summer.  It is yellowish or greenish with long, fine white hairs with two rows of black spots down its back, growing to about one inch long when fully grown.  However, an easier way to identify fall webworm is from the silken webbing that covers the ends of branches where the caterpillars feed in nonsocial groups.  These caterpillars feed on the leaves of over 100 different species of deciduous trees and shrubs, including black walnut, birch, ash, crab apple, elm, and maple.  

Fortunately, fall webworm normally has little impact on the health of large, vigorously growing, well-established trees (it is possible that small trees or shrubs can be completely defoliated in one season and could be injured).  Fall webworms are usually no worse than an eyesore because of the webs they construct, making management …

The "Cursed" Thistle - Canada thistle Cirsium arvense (L.) Scop.

Karl Foord, UMN Extension Educator



Photo 1: Canada thistle rosette in lawn.

Whenever I weed my gardens I always manage to find a number of Canada thistle plants, Cirsium arvense (L.) Scop. These are not the rosette seedlings that I see in my lawn which are fairly easily dealt with (photo 1). These are aerial shoots coming from established roots (photo 2). A mixed planting garden bed presents its own set of problems in dealing with this weed. Why is Canada thistle so persistent?


Missouri State University
Photo 2: Canada thistle underground root structure and aerial shoots.
Canada thistle is persistent for three reasons. Seed production, deep roots giving rise to stems, and root pieces that can regenerate plants.

Seed production per plant averages 1,500 seeds per plant but vigorous plants have been known to produce more than 5,000 seeds with viabilities greater than 20 years. So it will take persistence to reduce the seed load in the soil. Lesson 1: never let thistle go to seed. This wi…

Preserving the Harvest: Growing Everlastings in your Cutting Garden

Robin Trott, UMN Extension Educator, Douglas County


Robin Trott
Helichrysum (strawflower).
My house has been full of beautiful floral arrangements all summer, and the fall arrangements are outstanding, however, we will soon enter the cold months, and I can't envision a house without the color from my garden. To avoid this, I have made sure to include some everlasting plants in my cutting garden: Limonium sinuata (Statice), Helichrysum (Strawflower), Gomphrena, Achillea (Yarrow), Celosia (Cockscomb), and ornamental Grasses are all good candidates for air-drying. Once dried, I use these everlastings in bouquets, sachets, wreaths and holiday crafts.


Robin Trott
Echinacea (purple coneflower).
Harvest your everlastings when the flowers are not fully open and in good condition. Don't wait too long, because flowers too far along will not dry satisfactorily. Select flowers or seed pods that are as close to perfect looking as possible because flaws, such as insect damage, become more…

Swarming Ants During Late Summer

Jeffrey Hahn, Asst. Extension Entomologist


Jeff Hahn
Photo 1: Field ant swarmers

There have been numerous sightings of winged ants during August and September throughout Minnesota. These winged ants are reproductives, i.e. new females (soon to be queens) and males. The fly out of their nests at the same time, usually in large numbers for the purpose of mating. After mating, the queens fly off in search of favorable sites to build their own nests and the males die shortly afterwards.

Although nearly all ants swarm, different species do so at different times of the year. Right now cornfield ants and field ants are the primary swarmers that are active. Both of these ants nest in the soil in exposed sites and can be commonly found in lawns and other turf areas. Cornfield ant queens are about 1/4 inch long while field ants are a little larger.

Because of their size, field ants are sometimes mistaken for carpenter ants. However, carpenter ants do not nest in the soil and swarm just d…

Black Leaves on Black Eyed Susan

Michelle Grabowksi, UMN Extension Educator


J. Beckerman
Photo 1: Septoria Leaf Spot on Rudbeckia

This time of year the beautiful display of yellow flowers put on by Black Eyed Susan plants (Rudbeckia sp.) is often ruined by the plant's leaves turning partly or completely black. The leaf discoloration is caused by the fungal pathogen Septoria rudbeckiae. This pathogen causes dark brown to black leaf spots much earlier in the season. The disease often begins on the lower leaves of the plant and may go unnoticed. As the season progresses, so does the disease.

By September, plants may not have a single green leaf remaining. Septoria rudbeckiae will survive in plant debris, so it is best to remove infected stems and leaves at the end of the season. These should be discarded in a backyard compost that gets hot or at a municipal composting site. Next year, thin plants and remove volunteer seedlings to provide good air movement around plants. Water with drip irrigation or early in the day…

Q&A: What is the Implication of the Freeze Warning on Apple Crops?

Julie Weisenhorn
Emily Hoover, professor and department head, UMN Department of Horticultural Science

Question: What is the implication of the freeze warning on the apple crop?

Answer: It depends on how cold it gets. The temperature within an orchard is not consistent. The "rule of thumb" is about 10% of the fruit on the tree will freeze if the temperature drops to 28 degrees Fahrenheit and remains so a few hours. Ninety percent of the apples will freeze if the temperature drops to 25 degrees Fahrenheit and remains so for a few hours.

However, the level of sugar in an apple also changes the severity of the event. The higher the amount of sugar, the lower the temperature has to be before freezing will occur because sugar lowers the freezing point of a solution. (Think Chemistry 101). Note that if the fruit freezes on the tree, but is not touched until it thaws, the fruit is fine to harvest.

Emily Hoover is a professor and department head in the UMN Department of Horticultural…

Calendar: September 15, 2011

Bridget Barton
Three-Mile Drive at the Minnesota Landscape Arboretum, October 2010.
According to the Minneapolis Star Tribune, the Minnesota DNR is predicting the best fall color in ten years, thanks to abundant rain during the growing season, as well as a hot, humid summer. The DNR fall color reports are now available, to help find the most vibrant color in the state. The University of Minnesota Climatology Working Group, a division of the DNR, has more interesting information about the cause of the spectacular color show we enjoy each fall.

The Minnesota Landscape Arboretum and the Minnesota Grape Growers Association are teaming up for the upcoming collaborative, 4X4 Culinary Series at the Arboretum. For the series, U of M Enologist Katie Cook will lead participants through four food and wine pairings over a series of four dinners prepared by leading Twin Cities chefs. Participants can sign up for any or all of the dinners to experience a full array of local wines and meals this fa…

Emerald Ash Borer Found in Two New Sites

Jeffrey Hahn, Asst. Extension Entomologist


Jeff Hahn
Photo 1: EAB on purple trap
Emerald ash borer (EAB) has been confirmed in two new locations by the Minnesota Dept. of Agriculture (MDA) on Friday August 26. One find was detected in the city of La Crescent in Houston county while the second was found in the Great River Bluffs State Park in Winona county, just eight miles apart. This is the first time EAB has been found in Winona county. Both discoveries were made when an EAB adult was found on sticky purple panel traps that were deployed by the MDA. No infested trees have been found to date, although surveys in those areas are ongoing.

For more information see the MDA news release. Late Breaking News:  On Wednesday August 31, MDA reported that EAB was found on another purple trap about 7 miles northwest of the positive trap location at Great River Bluffs State Park and about 7 miles east of Winona. 


September Ushers in Prime Time for Home Lawn Care Activities

Bob Mugaas, UMN Extension Educator



Bob Mugaas
Late summer lawn and landscape.



The arrival of the Minnesota State Fair and its wrap-up on Labor Day weekend, mark the beginning of one of the best times of the year for initiating and renewing home lawn care activities. When it comes to repairing and rejuvenating your lawn after it has endured the stresses of another summer, avoid the temptation to also be winding down your lawn care efforts once Labor Day has passed. The main reason is that our grass plants are entering a very active period of growth triggered by a shortening of the days, cooler temperatures and usually a return to more frequent rainfall. Following are a number of brief lawn care tips that can help restore any lawn's health and vigor.

1. The middle of August through the middle of September is one of the best times of the year for lawn renovation and reseeding. Practices such as dethatching and aerifying are all best done at this time of year. Again, the primar…

Giant Swallowtails

Jeffrey Hahn, Asst. Extension Entomologist



Wendy Pritchard
Photo 1: It's a treat to see a giant swallowtail

There have been several reports of people seeing giant swallowtails, Papilio cresphontes, in the Twin Cities areas recently (they undoubtedly have been seen in other areas of Minnesota as well). This is noteworthy as these spectacular butterflies are not native to Minnesota but can occasionally be found during the summer as migrants from the south.

You can recognize a giant swallowtail because of its size, its wingspan ranges from 4" - 5 ½", and its black wings with yellow spots; the yellow spots on the forewings form an 'x'. Don't confuse it with a black swallowtail which also has black wings but is smaller, its wingspan is as large as 3 ½" and the yellow spots on its forewings are parallel and do not cross. Giant swallowtails can not reproduce in Minnesota as they need citrus trees and related plants for food for the larvae.