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Friday, March 30, 2012

Some Questions About Japanese Beetles

David Cappaert, Michigan State University,

Photo 1: Japanese beetle grub

Jeffrey Hahn, Asst. Extension Entomologist

There have been a lot of questions concerning Japanese beetles (JB) as we go into the 2012 growing season.  JB has been increasing in numbers over the last four or five years, especially in the Twin Cities area, although JB are also starting to be found more commonly in other areas of the state as well.  They can be challenging to control and people will take any steps they can to reduce their numbers in their gardens and yards.

The first question people ask is how bad are JB going to be this year.  There isn't an easy answer to that question and it undoubtedly will vary according to where you live.  If JB was abundant last year, there is a good chance they will be common again this summer.  However, a factor that can have an impact on JB numbers is soil moisture.   The eggs and the young grubs have a harder time surviving in dry soil so if dry conditions exist when JB are laying eggs, that can reduce the numbers of adults that are seen the following year.  Of course, if the turf area is well watered, that will make it easier for JB to survive.

It is difficult to determine what role the winter weather had on JB populations.  Although the mild temperatures favored JB, the lack of snow cover could have been potentially detrimental to them.  The early spring we have been experiencing should not have any effect on JB numbers.  However, expect them to emerge earlier than normal.  In a typical season, JB emerge around the 4th of July.  If the weather holds, the adults could be active as soon as the 3rd or 4th week of June.

And speaking of the early spring, people are wondering whether they can still treat JB grubs this spring or whether it is too late.  An important to factor to first consider is whether your primary goal is to control the grubs, because you are seeing damage in your turf, or the adults because of damage they have done to garden and landscape plants.  If your aim is to reduce the adults by controlling the grubs, you can save yourself the effort as this is not effective.  The adults are mobile and can easily fly in from areas outside your property. 

If you are finding turf damage due to JB grubs, and if you have had a lot of adults on your property look carefully for this, then the best time to treat for grubs is in July.  If you are going to use a preventative, such as imidacloprid (e.g. Merit), then you should be treating your turf when you first see the adults flying.  About two to three weeks after the first adults have emerged, JB eggs are hatching.  Preventative insecticides are most effective against the first instar larvae but not the older second and third instar larvae so the timing is critical. 

If JB grubs are not treated then, it is still possible to control them with a curative insecticide, such as trichlorfon (e.g. Dylox).  You can effectively treat JB with a curative insecticide until about mid-August.  By spring, the grubs are too large to effectively treat them.

Thursday, March 1, 2012

Contents: March 1, 2012

In this issue of the Yard and Garden News:

A Bee Lawn: How to Have an Insect Haven in Your Lawn

Editor's note:This is the first in a series of articles written by Dr. Meyer on diversifying the grass in your yard and garden.

Watering Orchids: Roots Tell the Story

Avoid Damping off of Seedlings

A Bee Lawn: How to Have an Insect Haven in Your Lawn

Mary Meyer, extension horticulturist and professor, University of Minnesota

As a grass researcher and lover of grass, I enjoy and appreciate a lawn. I also know there is great value in a lawn that allows and encourages a diversity of plant species that will benefit pollinators while looking neat and tidy for our neighbors to accept. First of all, let me state that I have had more questions on how to NOT attract bees to lawns, and how to eliminate bee plants (such as creeping Charlie) than on how to attract bees to lawns. When you have young children sitting on the lawn, rolling on the lawn and playing outside, bees can be a problem that you want to avoid. But for adults and taller folks, we can easily avoid bees in lawns. And knowing that bees are vital pollinators that need our help with increased habitat, I urge you to look at your lawn and consider where part of it may become a haven for bees and other important pollinators.

What is a bee lawn?

My definition of a bee lawn is a combination of traditional cool season lawn grasses and other low growing plants that support bees and native pollinators (Photo 1).

Mary Meyer

Photo 1: Bee Lawn

This combination must tolerate some mowing and foot traffic. From a distance this combination will look like a lawn, but when you walk on it you see it is much more diverse.
Reasons to foster a bee lawn:
• Plant diversity is good for the environment, can improve soil health and supports a wide variety of insects, birds and wildlife
• Flowering plants provide pollen and nectar for pollinators which will help increase and stabilize their numbers
• Legumes such as clover can increase soil nitrogen and reduce the need for supplemental fertilizer on lawns
• A diversity of plants in your lawn will make it less susceptible to disease, insect or drought damage

Where to grow a bee lawn

Plants that bees love need full sun more than water or fertilizer. If you have a sunny slope that is problematic for mowing, consider making the area a bee lawn and only mowing a few times a year. A few bee plants like Lamium tolerate shade, but are ground covers and are not lawns; most bee plants that will grow in a lawn are sun loving plants.
You may be uncomfortable with this look in your front lawn, especially if you are concerned about the neighbors wondering about your level of lawn maintenance. However, in your back yard it may be aesthetically easier for you to tolerate and allow clover and other legumes and short mint-type plants grow.
If you do need an area for children, decide on which section will best fit children's needs i.e. flat for running and sports, etc.
If you have a vegetable garden, you may want a bee lawn nearby to assist in squash pollination; if you have fruit trees, you may want the ground cover under the trees to become a bee lawn, encouraging pollination for increased fruit set.

Guidelines for Developing a Bee Lawn

Mow your lawn at 3-4", longer grass will withstand more drought and may allow some legumes to begin to grow. Consider mowing once a month, or as needed to maintain the appropriate appearance of a longer lawn.

Over seed your lawn with white and alsike clover. These two species of clover are excellent bee plants. Both are short, can be mowed and produce an abundance of small flowers that bees are fond of. For traditional lawn lovers, white clover (Trifolium repens) and alsike clover (Trifolium hybridum) are weeds. However, both species attract several kinds of bees, including honey bees, and the seeds of white clover are eaten by many birds and waterfowl. Both species grow easily on most soils, and tolerate some mowing and foot traffic. And both fix nitrogen, increasing the nitrogen available for grasses growing nearby.

Reduce or strictly limit the use of herbicides and insecticides. You can selectively kill any broadleaf weeds that you do not want with a spot treatment herbicide. Clover and all other bee friendly plants listed in this article are easily injured and usually killed with herbicides. Bees and insecticides do not co-exist. It is a trade off, so consider the risks each time you are thinking of using either an herbicide or insecticide.
Plant bee's favorite plants: These plants are bee favorites, but are also short and tolerate some mowing and minimal foot traffic: most any of the mints, especially self-heal (Prunella vulgaris), bird's foot trefoil (Lotus corniculatus), and thyme (Thymus spp.). Squill (Scilla siberica) is an early blooming small bulb that can be naturalized in lawns, along with crocus (Crocus spp.) that attract bees early in the spring. Wait a few weeks until the foliage from these bulbs has yellowed before mowing in the spring.

Grasses for bee lawns

Fine fescues are the lowest maintenance grasses: sheep fescue (Festuca ovina), chewing's fescue (Festuca rubra ssp. Fallax), creeping red fescue (Festuca rubra), and hard fescue (Festuca brevipila) are all good low maintenance grasses. These grasses all tolerate low fertility soils, are drought resistant and tend to mound or fall over, providing a cover for bees that nest in the ground. Shady lawn seed mixes are usually fine fescues.

Mow high and just see what grows? This is the 'least work' option and may or may not result in bee plants. You may get a very weedy and unsuitable look with plantain, knotweed and crabgrass, none of which are bee favorites. Bees, however do not discriminate and have no idea what weeds are, they love dandelions and creeping Charlie.

A last word on ground ivy, creeping Charlie (Glechoma hederacea): bees love this plant and will benefit from your leaving it in your lawn. Most of us know, however, that this aggressive mint can become the lawn if left to grow in low fertility, especially shady, areas. I love it in my backyard bee lawn along with violets (not so good for bees, but larvae food for some butterflies), but in my front yard I prefer grasses and flowering bulbs and keep the ground ivy at bay.
Consider where a bee lawn can fit into your landscape. As conscientious gardeners, we need to support bees and pollinators.

For more information:
The Xerces Society. 2011. Attracting Native Pollinators: Protecting North America's Bees and Butterflies. Storey Publishing
The Bee Lab at the U of MN:
The Xerces Society:

Watering orchids - roots tell the story

Karl Foord - University of Minnesota Extension

It is not often that a plant can through a visual color change indicate its need for water, however the aerial roots of tropical epiphytic orchids indeed do. Epiphytes are plants that grow on other plants or structures but are not parasitic (Photo 1).

Photo 1: Epiphytes on Tree

They derive their moisture and nutrients from air, rain and nearby debris. Most of the orchids used as house plants are tropical epiphytes.
The roots of these plants not only serve to anchor the plant to trees or stone, they also function as water storage units capturing water during rain events. The roots have a unique structure that enables them to absorb and store water. Phil Gates, a botanist at Durham University in the UK, has a blog entitled, Beyond the Human Eye - An insight into a microscopic world, invisible to the unaided human eye. He has sectioned and photographed an orchid root (Photo 2).

Phil Gates

Photo 2: Sectioned orchid root

The xylem vessels that conduct water from the roots to the leaves consist of the ring of bright yellow cells at the bottom of the photograph. Surrounding the xylem vessels is a layer of blue packing cells. Exterior to the packing cells is a row of hexagonal cells beyond which are a layer of dead cells called the velamen layer. The velamen layer functions as a sponge soaking up water as the aerial roots are exposed to rain or mist. Interestingly the velamen layer changes color based on water content and is an excellent indicator of the plant's water status. Dry velamen reflects light and is white or silvery (Photo 3),

Phil Gates

Photo 3: Dry orchid root

but when the velamen absorbs water the green tissue underneath becomes visible and the root takes on a green or mottled green color depending on the species (Photo 4).

Phil Gates

Photo 4: Wet orchid roots

Avoid Damping Off of Seedlings

M. Grabowski, University of Minnesota Extension

M. Grabowski, UMN Extension

Photo 1: Cucumber seedlings suffering from damping off

Damping off is a fungal disease caused most commonly by the fungi Rhizoctonia spp., Pythium spp., and Fusarium spp. All three of these fungi survive quite well in soil and plant debris. Since the tissue of young seedlings is soft and easy to infect, these pathogens can attack a wide variety of flowers and vegetables when they are seedlings. Damping off fungi can kill the seed before it emerges from the soil or it can attack the young stem and new leaves, resulting in tan mushy spots, pinched, rotted stems, and often complete collapse of the seedling. Once an infection has begun, the damping off fungi can move through the potting mix to infect nearby seedlings. Quite often a large section or an entire tray of seedlings is killed by damping off, resulting in few or no surviving seedlings to grow into mature plants.

Damping off is only a disease of seedlings. Once plants have mature leaves and a well developed root system, they are better able to naturally resist the damping off fungi. There is a critical period of growth where special care needs to be taken to protect sensitive seedlings. This period begins before the seeds are ever planted. One of the most import strategies of controlling damping off is preventing it in the first place. Since the damping off fungi typically survive on plant debris, soil, or in contaminated water, all pots, trays, potting mixes and other planting equipment must be sterilized prior to planting. New trays, pots, and potting mix are typically sterile. If you are reusing last year's pots and trays, they should be soaked in a 10% bleach solution for about 30 minutes. It is best to use new unopened potting mix to start seeds.

M. Grabowski UMN Extension

Photo 2: Fungal growth on a cucumber seedling suffering from damping off

Once seeds are planted, it is important to maintain a good growing environment for the seed. Potting mix should be moist but not soggy. The damping off fungi thrive in wet cool conditions. Many types of seeds, like tomatoes, need warm soil to germinate and grow well. Warming mats designed specially for heating seedling trays from below are sold through many garden catalogues and nurseries. These may be very helpful in preventing damping off especially if seeds are being grown in cool areas like a basement or garage.

Careful attention should be paid to watering seedling trays. Seeds need moisture to germinate, but too much water will encourage damping off. All pots and trays should have drainage holes to allow excess water to drain away. Seedlings should be watered with lukewarm clean water (like tap or other drinking water). Watering with cold water will slow seedling growth and favor the damping off fungi. Hoses and watering heads should be kept off the floor where they could come into contact with infected soil or plant debris. An oscillating fan can be used to increase air flow around the seedlings, but care should be taken to avoid over drying of the sensitive new plants.

Cultural practices that result in tall, thin, weak plants like growing plants under low light conditions or over fertilizing with nitrogen will result in increased damping off problems. Provide seedlings with just enough of what they truly need.

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