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Extension > Yard and Garden News > Archives > November 2009 Archives

November 2009 Archives

An Interesting Insect Found In a Home Yard

Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist

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Photo (above): Northern mole cricket. Jeff Hahn.

An unusual insect, a northern mole cricket (Neocurtilla hexadactyla), was submitted to the entomology department in August. This insect was found by a homeowner in their yard in North Branch (Chisago county) in east central Minnesota. Northern mole crickets are found throughout the eastern U.S. in low lying moist areas, e.g. along the margins of lakes and streams. They are rarely found in home lawns and are not considered to be a pest in Minnesota.

This brown insect grows up to 1 1/4 - 1 1/3 inches long, has moderate length antennae and short wings that only extend about half way down its abdomen. What is particularly distinctive about this insect is its stout, mole-like front pair of legs which are modified for digging (called fossorial). They have four dactyls (claws) on their tibia which distinguishes them from closely related mole crickets. Despite their ungainly appearance, northern moles crickets are capable of flight, flying at dusk.

They spend essentially their entire life underground where they feed on grass. If a northern mole cricket is exposed, its first reaction is to dig back down into the soil.

They take two years to develop into adults. Females lay eggs in spring in chambers in the soil. The immature nymphs develop slowly and spend the first winter as nymphs. They eventually mature the second year wintering as adults.

A northern mole cricket is a relatively uncommon insect in Minnesota, but even less commonly noticed by people due to its secretive habits. Interestingly, a number of eastern states also reported encountering this insect this summer in instances when they normally do not. It will be interesting to see if this a future trend or if this year was just a good year for northern mole crickets.

Fungi Sprouting on Trees Have a Scary Story to Tell

Michelle Grabowski, University of Minnesota Extension Educator

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Photo 1 (left): Basidocarp of Climacodon septenrionalis. Michelle Grabowski.

With October's frequent rain, many gardeners have noticed fungi sprouting from some landscape trees. These fungi may be any number of shapes, sizes and colors. They may arise from the trunk itself, from the root flare of the tree or from the roots. In all cases, fungi growing directly on a live tree tell the tale of heart rot within.


What's in the Trunk?

In order to understand heart rot, gardeners must understand a little bit about the wood within a tree trunk. Trees can have several different kinds of wood within their trunk. Sapwood is composed of living cells with a number of jobs to do. Sapwood cells conduct sap through the tree, store extra energy, close off wounds, and actively fight invading microorganism. In all trees, sapwood occurs in the outer most rings of the tree. Some trees, like maple, birch, beech and poplar form only sapwood. Other trees also form a second type of wood, known as heartwood at the core of their trunk. Heartwood cells are dead cells that serve primarily to add structural support to the tree. Heartwood cells contain a number of toxic chemicals that protect the heartwood from wood decay fungi. How well these chemicals protect the heartwood varies from tree to tree. Trees like cedar and redwoods are so effective at defending against wood rotting fungi that their wood is highly valued for use in wood products like lumber.

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Photo 2 (above): Internal decay shown on cut trunk.

Heart rot can cause decay in both heartwood and sapwood. Many different fungi from the phyla Basidiomycota, can cause heart rot. These fungi are often seen on rotting logs or dead trees as well as on living trees. The mushrooms, shelf fungi and other interesting fungal structures that emerge in wet weather are spore producing structures of the fungus, and are generally known as basidiocarps. If a basidiocarp is observed on a live tree, it indicates that there is rot within the tree. Basidiocarps can be used to identify the specific fungi causing rot as they are often unique to a specific genera or species of fungus. <

How the Invasion Begins

Heart rot fungi are not aggressive pathogens and are unable to infect a tree through intact bark. Instead heart rot fungi take advantage of wounds from lawn mowers, weed whips, fire scars, deer rubbing, rodent chewing, frost cracks, broken branches and other injuries to access the sapwood and heart wood. Some heart rot fungi can also enter a tree through an old branch stub or through the trees roots. Once inside the tree, the fungi use a variety of enzymes and other chemicals to breakdown the wood for food.

The Progress of Decay

White rot fungi breakdown all components of the wood including lignin, cellulose and hemicellulose. Trees suffering from white rot have soft white wood that is stringy, spongy, or crumbly to the touch. Brown rot fungi break down cellulose in the wood but not lignin. Trees suffering from brown rot will have brown decaying wood that breaks apart into cube like chunks. This type of rot is often called brown cubical rot. In both cases advanced decay can significantly reduce the strength of the tree resulting in fallen branches or trees that break or fall over. Trees often survive many years with heart rot. Internal rot often goes unnoticed for years because the tree can continue to grow with no symptoms of disease or decline in the canopy. Remember heartwood cells are not living cells and serve only to provide structural support for the tree. If basidiocarps are observed on the tree, it is likely that the tree has already been infected for several years. The decay caused by many heart rot fungi progresses very slowly, often at a rate of about 3 inches per year.

Assessing Damage in an Infected Tree

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Photo 3 (above): Fungi, indicating butt rot on maple. Michelle Grabowki.

A tree with signs of heart rot does not need to be immediately removed, but it should be further examined to determine how structurally sound it is. Special care should be taken with trees that are located near people or property that could be damaged by fallen branches or trees. In natural areas, trees with heart rot serve a valuable function in providing nesting sites for birds and animals and should be left undisturbed if possible. The stability of a heart rot infected tree will vary depending on the type of tree that is infected, the extent of the decay, the type of rot, and if other defects like cracks or cavities are present. The USDA Forest Service (http://www.na.fs.fed.us/spfo/pubs/howtos/ht_haz/ht_haz.htm ) recommends that action be taken to stabilize or remove a tree if it has signs of a heart rotting fungi and one or both of the following:
 
  •  a crack, open wound or other defects are also present
  •  less than 1 inch of solid wood for every 6 inches of tree diameter.
The level of internal decay can be difficult to determine if an open cavity is not present. Gardeners concerned about the structural stability of a tree should contact the local city forester or a certified arborist (www.treesaregood.org). These professionals can run a variety of tests to help assess the stability of the tree.

 

Preventing Heart Rot in Trees

Gardeners can prevent heart rot by protecting the trees most important natural defense - its bark.
 
  • Take care not to wound trees with lawn care equipment.
  • Protect trees from deer rubbing and rodent damage with fencing.
  • Use proper pruning cuts when pruning trees and never leave a branch stub (see: http://www.extension.umn.edu/yardandgarden/YGLNews/YGLNewsMar12007.html#pruningcuts).
  •  If branches are broken during a storm, cut damaged branches with a proper pruning cut below the damaged area. The tree will be able to heal a smooth pruning cut more quickly than a rough jagged rip.
 

Dormant Seeding Lawns: Last chore of the season?

Bob Mugaas, University of Minnesota Extension Educator Thumbnail image for Thumbnail image for Thumbnail image for Thumbnail image for Thumbnail image for Picture 1-DS.JPG

Photo 1 (above): Thin lawn area that could benefit from dormant seeding. Bob Mugaas.

One last shot at lawn improvement can be done even yet this fall. By early November, most lawn care chores and activities are completed; lawn mowers are put away, watering has ended, hoses are drained and stored for the winter, irrigation systems have been blown out and winterized and, the last, late season nitrogen fertilizer has been put down.  Yet, there remains one activity that can still be done to help repair or thicken the lawn for next year. In fact, prior to the early part of November (at least in the Twin Cities area, earlier in the northern half of Minnesota), it would be have been too early to do this task. That task is known as dormant seeding.  It is best employed when wanting to reseed bare soil areas or help thicken up thin lawns. It is not as effective, where lawns are thick and dense with little opportunity to achieve the good seed to soil contact necessary for the grass seeds to germinate and grow next spring.

The Dormant Seeding Process

Dormant seeding involves putting down seed while the ground is not frozen, yet cold enough so germination of the grass seed will not occur until next spring when the soils begin to warm. In fact, seeds that do germinate late in the season often do not survive the winter because the very young, immature seedlings have a difficult time surviving those harsh conditions. Other than the time of year of dormant seeding, the actual process of preparing the area to be seeded is virtually identical to establishing grass from seed at other times of the year.

Choosing Well Adapted Seed

When choosing the seed to use, be sure to select seed mixes that are well adapted to both your site conditions and the amount of maintenance you expect to provide during the growing season. For average lawn conditions, mixes containing some Kentucky bluegrass, fine fescue and small amounts of perennial ryegrass can be sown about three to four pounds per 1000 ft2.

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Photo 2 (left and above): Vertical rotating tines of a vertical mower, sometimes termed a power rake. Bob Mugaas.

Establishing Good Seed to Soil Contact

Success of any grass seeding process depends largely on good seed to soil contact. Therefore, the initial step in preparing the area is to loosen the soil surface so the seed can easily be incorporated into the surface half-inch or so of loose soil. Small areas of bare soil or even a thin turfgrass stand can easily be prepared using a hand rake. Larger areas of sparse turfgrass can be prepared by 'lightly' going over the surface with a power rake or vertical mower available from most rental agencies. Set the blades just deep enough to penetrate into the top ¼ inch or so of soil. This will also help remove small thatch layers that may be present, as well as any dead grass plant parts laying on the surface of the soil.

Rake up the grass plant debris that was brought to the surface from this process so that it will not interfere with sowing the grass seed. This debris can easily be composted or used as a mulch in another area of the landscape. Remember these units are NOT intended to be used as rototillers. They are designed and used to remove thatch with only light penetration into the surface soil. Hence, use them appropriately; your rental service will appreciate your proper use of their equipment.


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Photo 3 (left): Using a vertical mower to prepare lawn/soil surface prior to seeding. Bob Mugaas.

Another machine known as a slit seeder could also be used. This machine creates a shallow slit in the soil into which the seed is dropped, lightly covered and packed down. There are some rental businesses that have such a unit available. More commonly this is a practice hired done by a lawn care professional.

Watering Thoroughly, but Not Too Much

Once the seeds have been properly sown and lightly incorporated into the existing soil, water the area thoroughly and leave until next spring. By this time of year, our cool to cold temperatures and short days will help keep the areas moist far longer than in summer. While just barely damp soil is okay, it is important that the area does not become soggy and saturated with water. If the weather does turn a little warmer and drier and the area starts to dry out,  it may be necessary to lightly water the area just to keep it damp and prevent it from becoming too dry.  However, in most cases it will be unnecessary to do this.

What to Expect for Next Spring

Above are the essentials for the process known as dormant seeding. The degree of success from your dormant seeding efforts will depend on the overwintering conditions afforded to the newly seeded areas. In most cases, the seed is best protected when we receive snowfall(s) that will cover and protect those areas during fluctuating weather conditions often experienced during a Minnesota winter. Even with good preparation, it may still be necessary to do some overseeding in the spring in those areas where little grass emerges. If the newly seeded areas appear to be a little thin, you shouldn't necessarily feel your fall efforts were a failure, as it is quite common to have to do a little additional reseeding in the spring. However, do allow enough time for the seeds to come up the following spring. Don't be too hasty to get in and start tearing things up; you just may be destroying all of the good work done the previous fall.

For those of you who postponed doing some lawn seeding earlier last summer, consider doing some dormant seeding yet this fall. It may be just the ticket to give you and your lawn a jump start next spring.

Edible Landscape Wrap-Up

Emily Tepe, University of Minnesota Research Fellow, Department of Horticultural Science

After many weeks of harvesting mountains of chard, tomatoes, zucchini, peppers, cucumbers, raspberries and a multitude of other vegetables, fruits and herbs, the University of Minnesota Edible Landscape has been put to bed. Well...almost. The few lone stands of silvery blue kale seem to mock the cold, their leathery leaves sweetening with each frosty night. And many of the herbs are even holding onto their green. Other than those, the Edible Landscape is now resting after a long and productive season. snow on kale_tepe.JPG

Photo 1 (left and above): Snow on dinosaur kale in the University of Minnesota Edible Landscape on October 12, 2009. Emily Tepe.

If you haven't had a chance to see the gardens on the St. Paul campus this year, and if you haven't been following the Edible Landscape blog, here's a rundown of some of the details of the project. The Edible Landscape filled four beds outside the Plant Growth Facilities on Gortner Ave. The 1500 square foot garden was comprised of 75 varieties of fruits, vegetables, herbs and flowers. The garden was designed to emphasize the ornamental qualities of edible plants, and demonstrate how these plants might be incorporated into the home landscape in creative, attractive ways. Most of the ornamentals, herbs and warm season crops were started from seed in the greenhouse during the winter months. Others, such as chard, kale, summer and winter squash, melon, lettuces and radishes were direct seeded throughout the season. By mid-October, almost 500 pounds of produce had been harvested from the Edible Landscape and shared with students, faculty and staff in the Department of Horticultural Science.

After cleaning all the annuals out of the garden (which were then composted), winter rye seed was raked into the beds for a winter cover crop. It may sound strange to think of cover crops in a home gardening demonstration. After all, we normally think of cover crops being used on acres of land, not in the backyard. But cover crops in the home garden can offer great benefits such as weed suppression, erosion control, increased microbial activity and moisture retention, just to name a few. You can read about Green Manure Cover Crops for Minnesota on the U of MN Extension Website.

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Photo 2 (right and above): The largest bed in the University of Minnesota Edible Landscape in mid-July. Emily Tepe.

If the idea of edible landscaping sounds intriguing, or if you would simply like to learn more about this project, visit the Edible Landscape blog. The entire season was documented on the blog, which is filled with photos, design ideas, plant lists, growing information and more. Now that the harvests have finished, and the season is being evaluated, there will be more discussions on the blog about plant combinations that worked well, successful varieties, and lessons learned. Read, learn, share and join the discussion.

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