Yard & Garden Line News
Volume 6 Number 16                                                               October 1, 2004
Features this issue:

Changes Underfoot!
Insects From Out of Town
15th Anniversary of Minnesota Gardening Calendar
Grape Downy Mildew
October Garden Tips
Editorial Notes


Changes Underfoot!
Robert Mugaas, Regional Extension Educator, Horticulture


Grass roots respond to climatic changes. Image Source: Low Input Lawn Care publication
There are some big changes going on beneath you - in your lawn that is!

As Minnesotans, we are accustomed to big weather changes that occur as we go from summer to fall and fall into winter. However, we usually do not spend much time pondering how the plants in our landscape may be adapting to those same conditions, particularly our lawn grasses. While individual weather conditions can change from day to day, it is the shortening of day lengths, dropping of average temperatures and (usually) more moisture in the form of rainfall that our lawn grasses respond to during the late summer to late fall period.

Most of us observe a surge of grass growth in the late summer to early fall period. This is a time when the turfgrasses are actively producing new rhizomes, stolons, tillers, and roots. Consequently, this period of active growth results in a thickening of the lawn. Our lawn grasses can easily fill in those small bare spots due to previous injury or damage from insects of diseases.

As our temperatures begin to drop consistently into the 30's and 40's, another significant change begins to take place in our grass plants. While top growth may have slowed to a standstill due to the cool temperatures, root growth continues at least at some level until the ground around the roots actually begins to freeze-up for the winter. However, the center of profound change in the grass plant is occurring in the tiny little growing points (meristems), called crowns.
Fescue with mature seeds. Photo credit:
Eric Watkins
The lowering of temperatures produce an effect known as vernalization and the shortening of days produce an effect known as photoinduction. What this means is that the growing points (meristems) which have been actively producing new vegetative plant parts are now 'irreversibly' being induced to change from vegetative growth to flower production by the consistently cooler temperatures and shortening of day lengths. This change results in the elongation of the growing point and the formation of the immature flower parts that will actually produce the flowering stems next spring. One important caveat for the grass shoot is that it must have been growing long enough to reach enough maturity in order to be "sensitive" to these environmental changes. Young, immature grass shoots continue to grow vegetatively through this period and, for the most part, remain insensitive to the temperature and day length stimuli. Once induced into the flowering mode, the grass plants remain in a relative state of suspended animation. That is, the remaining flower stem production cycle is carried out next spring. At that time, the advent of long day lengths stimulates the shoot to continue flower development and ultimately produce the flower stalks. "But I've never seen grass flowers in my lawn" you say. Well, as we begin mowing our lawns in the spring, we normally keep cutting off all or most of the flowering stem. Hence we never really do see grass flowers in our lawns. Although, if you're paying attention there are usually a few of those flowering shoots that become visible even if we are regularly mowing. It should be noted that these flowering stems are not necessarily very tall. Some can be as short as just a few inches in a regularly mowed lawn.

The fate of the flowering shoot is not a very happy one as it dies along with its accompanying root system within a few weeks after producing the flowering stem (culm). However, remember those immature shoots that did not respond to the cool temperatures and short days during the fall (2004), they continue to grow and help ensure that our lawn remains 'perennial' and in tact next year (2005). Most of them will reach maturity by the following fall (2005) to be induced into the flower production mode and ultimately flower the next spring (2006). In the meantime, a new crop of developing immature shoots produced during the summer and fall of 2005 will continue to carry the lawn on into 2006 and so the cycle is once again repeated and our lawns remain a perennial, active, dynamic growing system from year to year.

Just thought you might like to know what goes on beneath your feet - at least in the lawn.

Insects From Out of Town
Jeffrey Hahn, Assist. Extension Entomologist

Leatherjacket. Photo credit: Oregon State
It has been an interesting September as a couple of unusual, non-native insects and a slug were discovered in Minnesota.

The first insect was detected in turf in a home lawn in Golden Valley. A request for help was made by the homeowner to a city official to help determine why his lawn was damaged. An onsite inspection revealed a few unfamiliar insect larvae. They were over 1/2 inch long, with grayish, leathery, cylindrical bodies. They were also legless and lacked definite heads.

The insects were identified as crane fly larvae. The most common crane fly attacking turf is the European crane fly, Tipula paludosa (There is also a closely related species called the marsh crane fly, T. oleraceae). So far, European crane flies are restricted to the Pacific Northwest, primarily in Oregon, Washington, and British Columbia, where they first arrived around 1965 from southern and central Europe.

Their larvae, know as leatherjackets, feed primarily on grass roots in lawns and pastures. Low levels of crane fly larvae do not noticeably affect lawns. High numbers (25 - 30/square foot), however, can cause severe damage. Injured areas of lawn turn yellow or become bare. European crane flies are also been known to attack annuals, perennials, some vegetables and small fruit.

It is hard to say how much of the damaged lawn was due to crane flies as the number of larvae were not particularly high to be a major factor. Drought was originally suspected although there was more damage than what that could account for. It is possible that the injury is a combination of drought and insect damage, although additional inspection is probably necessary.

It is also unclear how the crane flies arrived here. They can be accidently transported to other sites in turf or other plants and soil. While the damaged turf was newly installed from earlier in the spring, the sod originated from the Midwest. The homeowner apparently has an collection of lilies which could potentially be the source of the crane flies.

European crane flies have not been found so far in Minnesota although the Minnesota Dept. of Agriculture is monitoring for their presence. For more information, check out their web site: http://www.mda.state.mn.us/invasives/craneflies/default.htm. It is not known whether this species of crane fly would survive winters in Minnesota.

European red slug
The presence of an unusual mollusc was discovered when a homeowner asked to have a strange slug identified that her neighbor found in her yard in the Twin Cities. It was identified tentatively as the European red slug, Arion rufus. This slug varies in color, being reddish, orangish, brownish, or even black. The latter half of the slug has conspicuously wrinkled skin. They are large molluscs, growing as large as four inches.

This slug species is not native to Minnesota but is found just in the Pacific Northwest. European red slugs are sometimes accidently transported in nursery stock from Oregon and Washington to other places in the U.S.

While this pest is likely to be a European red slug, a specimen need to be dissected and examined to be sure it is correctly identified. It is possible that it could be the black slug, A. ater which is also found in the Pacific Northwest. These two slugs can be easily confused as both can be reddish or black. Neither species would be expected to survive winters here in Minnesota.

Also of concern is the possibility that it is A. lusitanicus (no common name). This exotic slug is native to Europe but has not been found in the U.S. to date. It is also a large slug growing up to four to six inches with a reddish brown color (although this color is variable). This slug has a voracious appetite and eats almost any type of plant, including trees. It is considered an important defoliator of forests in Europe. It is not clear whether this slug would thrive in Minnesota.

Unfortunately, no specimens have been recovered so far. There have been continued efforts from the Minnesota Dept. of Agriculture to examine the yard where the slug was first found to recover specimens for identification. It is unclear what source was responsible for accidentally bringing it into Minnesota, although it is may have come from perennials that the homeowner purchased in the spring.

Yellowstriped armyworm Photo credit: Jeff Hahn
A third insect, the yellowstriped armyworm, Spodoptera ornithogalli, was found recently in Sibley county attacking tomatoes in a home garden. When newly hatched, these caterpillars are green. They grow to be about two inches long (the collected specimen was about an inch and a half). As a mature caterpillar, it is a mottled black with two cream-colored or yellow stripes running down its back. If you look at the front of the head closely you will find light yellow lines (sutures) that resemble an upside down ‘Y'.

This species can be found throughout the U.S. and into southern Canada, although its primary geographic range is the southeast U.S. It would be considered rare in Minnesota. Unlike the European crane fly and the European red slug which hitchhiked through commerce to arrive in Minnesota, the yellowstriped hitchhike armyworm got here on its own. It was carried north on air currents and eventually deposited into Minnesota.

This caterpillar is a general feeder, eating the foliage of many garden and agricultural plants. It is particularly fond of tomatoes and cotton and will also eat the fruit of these plants. Fortunately, any problems that occur with yellowstriped armyworm in Minnesota will be localized and infrequent. Handpicking is the only necessary control if you find yellowstriped armyworms in your garden. Yellowstriped armyworms are not known to survive winters in Minnesota.

Get the low down on this month's insect pests at Insects http://www.extension.umn.edu/projects/yardandgarden/EntWeb/Ent.htm


15th Anniversary of Minnesota Gardening Calendar
Deborah Brown, Extension Horticulturist

2005 calendar. The
15th Year!
It doesn't seem possible, but the new Minnesota Gardening calendar for 2005 is our 15th consecutive edition This popular publication has been produced by the University of Minnesota Extension Service and the Minnesota Agricultural Experiment Station since 1991. We know it has a wide and loyal following among Master Gardeners, University personnel, and gardeners throughout the state. Copies regularly go to Minnesotans who now live elsewhere – across the US and on other continents.

To celebrate its anniversary status – no mean achievement in this atmosphere of restricted budgets – we've assembled a calendar that combines our favorite photo for each month, along with the most valued garden and landscape tips. The calendar's special pages feature myriad new cultivars developed by horticultural plant breeders from the Agricultural Experiment Station in the years since we began publishing the calendar. There are more azaleas, chrysanthemums, blueberries, wine grapes, trees and shrubs – and, of course, Minnesota's favorite new apples, ‘Honeycrisp'TM and ‘Zestar!'TM

Based on information supplied be Professor and Extension Climatologist Mark Seeley, our spring frost-free map has been revised and made easier to read. Instead of ninety-plus county offices, the list of contacts for reliable garden and landscape information now includes eighteen new Extensional Regional Centers, along with details about the U's Department of Horticultural Science (including the Minnesota Landscape Arboretum) and other garden-related institutions.

The Minnesota Gardening calendar makes a great holiday gift for all your gardening friends and relatives. You can find it at gift and bookstores, garden centers, and extension offices throughout the state. You can also order the calendar on line. Paste this address into your browser: http://www.extension.umn.edu/distribution/horticulture/DG8101.html If you prefer, call the extension distribution center, 612-624-4900 (Metro) or 1-800-876-8636 (Greater Minnesota) for credit card orders.

Grape Downy Mildew
Janna Beckerman, Extension Plant Pathologist

First signs are angular lesions. Photo Credit: Janna Beckerman
Downy mildew has had a devastating impact on Minnesota grape growers this past year. Downy mildew is a fungal-like pathogen that rots flowers (preventing fruit set), clusters, and shoots. Foliar infection reduces sugar production for the remaining fruit, and severe infections result in defoliation, predisposing plants to winter injury. Severe epidemics, like we've experienced this year, may require several years before the plants recover.

Downy Mildew Symptoms
This year, the infection was first noticed on older leaves in the summer. Symptoms consist of small, angular, yellow to red-brown spots on the upper surface . Turning the leaf over, or examining fruit clusters reveals the sporulating pseudofungi . As the cells in the lesion die, the lesion turns reddish-brown. The entire lesion may drop out of the leaf, resulting in a shot-hole appearance. Severely infected leaves often die completely, and drop. On tendrils and shoots, early symptoms appear as water-soaked lesions where downy mildew growth eventually develops.

Fruit infection occurs during two periods in the growing season: When berries are just beginning to develop, and later in the season prior to fruit ripening. When infected young, berries turn hard and brown, and may become covered with the sporulating pathogen. During the heat of summer, little infection occurs as the environmental conditions heat up. However, a second infection period may develop during cool, wet autumn weather. These berries turn dull green instead of ripening. The fruit wrinkles, fails to mature, and may rot if infection is severe.

Causal Organism
Downy mildew is caused by Plasmopara viticola. Once regarded as a fungus, this organism is called a chromista, or pseudofungus. This point is important to stress as the fungicides labeled to control downy mildews are not generally effective against the "true fungi." The pathogen overwinters as thick walled spores in infected leaves and diseased shoots. The thick walled oospore germinates in the spring to produce a sporangium, another structure filled with spores. In the presence of water, the sporangium releases small swimming zoospores. When the zoospore contacts a suitable host, it encysts and produces a germ tube that enters the stomates, and the plant, from the lower leaf surface. Inside the plant, the pathogen rapidly grows throughout the plant tissues, and lesions appear 7-12 days later. Under cool, wet periods, the pathogen grows out through the stomates and produces a new crop of spores to repeat the cycle.

Disease spreads, affecting fruit.
Photo credit: Janna Beckerman
Management
At this point in the season, control of this disease is no longer possible. But you can prepare for next year! Sanitation is the key. Remove fallen leaves and berries from vines and ground after leaf drop. Upon dormancy, treat vines with a Bordeaux or lime-sulfur to kill any overwintering spores, and apply again at spring prior to bud break. If you grow multiple plants, consider cultivating the vineyard before bud break to prevent overwintering spores from infecting the newly developing vines in the spring.

Improving air flow and circulation are very important for disease control. Make sure plants are well spaced to increase airflow and reduce leaf wetness. When pruning, prune severely, selecting only strong, healthy, well-colored canes of the previous year's growth. Overly dense canopies provide excellent sites for infection, and prevent fungicides from reaching potential pathogens. Make sure plants are grown in southern or western exposures and receive all-day sun and good soil drainage.

Good plant health management aims to not only control diseases as they appear, but to prevent their appearance and severity. There are downy mildew resistant grapes. In general, the European vinifera (Vitis vinifera) varieties are very susceptible and the native American species (V. riparia) are very resistant. Not suprisingly, the hybrids between these varieties vary in resistance. Reportedly resistant varieties include Frontenac, Baco Noir, La Crosse, Leon Millot, Marechal Foch, Concord and St. Pepin. Moderately susceptible varieties include Swenson's Red, Chancellor, Niagara, and Delaware.

Finally, several fungicides are effective for controlling downy mildew when applied to prevent infection. These include fungicides containing the active ingredients of Mancozeb, Captan and Copper* (fixed coppers and Bordeaux mixture). All of these are highly effective for control of downy mildew. Incorporation of good cultural conditions, resistant cultivars and good pruning technique can go a long way in managing this disease for most homeowners.

*considered acceptable for use for "organic" disease management.

Please check out the new diagnostics web pages at
http://www.extension.umn.edu/projects/yardandgarden/diagnostics/


October Garden Tips
Beth Jarvis, Yard & Garden Line

Keukenhof Gardens, Netherlands Photo credit:
Beth Jarvis
Compiled from conversations with Patrick Weicherding, Bob Olson and Bob Mugaas, Regional Extension Educators and Deb Brown, Extension Horticulturist.

These recommendation are based on Twin Cities temperatures. Adjust for northern Minnesota.

Trees and Shrubs:
For all of October, the word is still water. Water all evergreens and young trees until the ground freezes. Water deciduous trees and shrubs as best you can until the leaves fall. Remember that lawn grass captures the vast majority of applied moisture, so water more than an inch within the dripline of trees. The soil should be damp at least 6-8". Please see: http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-Sept0103.html#water"

Pruning for cosmetic or structural purposes should wait until the dormant season. Remove diseased trees now.

Be sure all elm and oak firewood has been de-barked before storage.

If you bought any clearance sale trees or shrubs or have anything in pots not yet planted, get them in the ground by the middle of October.

Wrap any smooth-barked trees in your yard. Do NOT use paper wraps as they have been found to be ineffective. Use flexible plastic tubing/tree guards designed for that purpose. Maintain airspace of at least 1/4" between trunk and covering. These can be left on the tree as long as there is airspace between tree trunk and the tubing.

The tubing does not protect trees from rodents. Protect you investment with 1/4" hardware cloth to surround tender-barked young trees. These surrounds need to be pressed into the soil to anchor them. They should be taller than anticipated snow drifts.

Lawns:
Keep watering you lawn as needed. Water is critical to keep grass actively growing as it stores food in the crowns and rhizomes. This is not the time to drought stress the lawn.

You can still apply broad leaf weed control in the very early part of October.

Apply 1# of nitrogen per 1,000 square feet for your later season fertilizer application. TC metro residents must buy phosphorus free fertilizer unless they have a soil test indicating need.

In northern MN, late season fertilizer is applied mid to late October. In southern MN, late season fertilizer dates are is late October to early November.

Be sure to water in the late season fertilizer application with 1/4 to -1/2" of water.

The ground must be thaw when you put the fertilizer down. Never put fertilizer on frozen soil.

Sodding is still possible in early to mid-October, then after that it depends on weather.

Reduce mowing heights gradually during October. A reduction from 3" to 2" should be done over 3 mowings which means you will need to mow a bit more often as you don't want to let the grass grows back to its former height before mowing again.

Leaves can mulched back into the lawn using a mulching mower or with a side discharge. The leaves should be dry. You'll probably need to run over them a couple of times. Protect your face from the dusty debris.

Core aerating is still possible. Dethatching should wait until spring. If you have heavy thatch, do a real thorough core aerating job now. Grass needs 6-8 week of recovery time.

Everything you ever wanted to know about lawn care and repair can be found at the Sustainable Urban Landscape Information Series website at: http://www.sustland.umn.edu/maint/index.html. Click on lawn maintenance and scroll down to the lawn care calendar for timing.

Naturalized daffodils in lawn.
Photo credit:
Beth Jarvis
Flowers:
Dahlias, caladiums, cannas, callas, gladiolus, tuberous rooted begonia and other tender bulbs can be dug now. No need to wait for the first frost. The bulbs/corms/tubers should be layered in peatmoss in stored in a cool spot until it's time to plant them anew.

Some research suggests that cutting perennials down to several inches is a task that should be left until spring. Plants like mums overwinter more successfully when they have a larger plant mass to catch snow. Snow is an insulating winter mulch.

As foliage is killed by frost or turns yellowish or reddish, it's ok to cut those plants down.

Wait until the ground freezes to mulch. Have material set aside. If it snows before the ground freezes, it's ok to mulch over the snow.

October is still a good time to plant bulbs. Minor bulbs (eg: squill, crocus, grape hyacinths) need to goin the first week or two of the month. Tulips can go in last.

Fruit and Vegetables:

Apples, Pears, and Plums. Pick up any windfalls and remove from orchard. Eliminate any dried fruit "mummies" that remain on the trees.

Harvest pumpkins and gourds as vines die. Store in a warm, dry location for a couple weeks to toughen the skins. Then store in a dry, cool location for long term storage.

Know the optimal storage conditions for your garden produce. Does it require "cool and dry", "cold and moist", or "cold and dry" conditions? Check out Harvesting and Storing Home Garden Vegetables at http://www.extension.umn.edu/distribution/horticulture/DG1424.html

Allow asparagus tops to remain standing when possible. The top growth catches more snow for overwintering success.

As your annual vegetable garden winds down, collect a soil sample and have analyzed for lime and fertility applications this fall.

Resist the urge to prune fruit trees after harvest. Wait until late winter or early spring for this task.

Modifying soil pH. Fall is a good time to modify soil pH if a soil test indicates changes are necessary. Before making any modifications, do a soil test. Crop lands tend to be more acidic so it would be fine to increase pH with lime products following harvest. Apply the recommended amount of limestone and till into the top 6 inches. Much of the TC metro/residential area has alkaline soil. If your soil is more alkaline, you'll probably need to lower the pH by using elemental sulfur or iron sulfate. Most garden plants do best in mildly acidic soil. Iron, calcium and magnesium levels are adversely affected by high soil pHs. (East coast garden writers who garden in acidic soil assume *everyone* needs to add lime.)

Editorial Notes

Windowbox
dahlias, from seed. Photo credit:
Beth Jarvis
Well, it's the first of October so we now return to a first of the month only publishing schedule until next April.

The dahlias at left were planted from seeds but by fall, had produced typical, though smallish, dahlia tuberous roots.

For the next issue, a grad student will write about the physiological changes plants, other than turf grass, undergo in order to flower. For November 1, Patrick Weicherding, Regional Extension Educator, Forestry, will be writing about new research findings on the timing of pruning trees for disease prevention and to prevent pruning damage.

Please feel free to cut and paste any of the articles for use in your own newsletters. All we ask is that you give our authors credit.

Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/yardandgarden/.

Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Thursday of every month at 10 a.m. The program is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations. (Scroll down for map.)

For plant and insect questions, visit http://www.extension.umn.edu/askmg. Thousands of questions have been answered, so try the search option in the black bar at the top left of the board for the fastest answer.

If you would like to receive an e-mail reminder when the next issue of the Yard & Garden Line News is posted to the web, just send an e-mail to: listserv@lists.umn.edu (note: the second E in listserve is omitted), leave the subject line blank, then in the body of the message, type: sub yglnewslist or to unsubscribe, enter: unsub yglnewslist


Beth Jarvis
Yard & Garden Line Project Coordinator


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