In this months issue:
November 2012 Archives
Sam Bauer, Extension Turfgrass Educator
There's no question that the fall drought has taken a major toll on many of the turfed landscapes in Minnesota. If you failed to maintain turf health through supplemental watering from August to October, you most likely have yet to make a damage assessment of your lawn. During the summer months we talk a lot about letting our lawns go dormant during a drought and waiting for rain to replenish soil moisture. This is nothing new. However, the duration of the fall drought has pushed our lawns to the limit, probably passed the limit in many cases. There are two main concerns: 1) how long can turf stay alive in a dormant state?, 2) will drought stressed turf properly harden off and survive the winter?
How long can turf stay alive in a dormant state?
There are no clear answers to this question and it really depends on many factors, including: turf species, traffic, management practices, and site conditions. We commonly hear that Kentucky bluegrass can survive for up to 2 months under drought dormancy, but there is no definite time frame due to all of the variables. From my experience, as long as the crown of the turf did not completely dry out, it should still be alive. I've been encouraging home owners to utilize the last part of the growing season (October) by watering to bring the lawn out of drought dormancy before winter. If you've done this, you should have a good idea just how bad the damage is.
Will a drought stressed lawn survive the winter?
Probably not, and chances are that it may be dead already if you didn't provide at least some supplemental watering to keep the crown from drying out. Turf species will play a very important role here. Perennial ryegrass will be the least tolerant of drought conditions and cold temperatures. You can check to see if your lawn is alive by taking a small sample indoors. Water it and place it on a window sill. You should see some growth in two weeks time.
Last chores of the season
By now you should have completed your last watering, mowing, and fertilization of the season. If you did not keep up with watering this fall and fear the worst, dormant seeding in mid-November will be a great option. For that I would like to direct you to a couple of links. The first link is a great discussion previously published in the Yard and Garden News by Bob Mugaas, retired Extension Turfgrass Educator. Bob discusses the most important factors for dormant seeding, including: choosing the right seed, seed to soil contact, and post seeding management. The second link is from the Virtual Field Day that we held this fall. In it, Dr. Eric Watkins professor of Turfgrass Breeding and Genetics discusses your turfgrass species options for Minnesota lawns. I encourage you to consider all of the species characteristics when choosing the turf seed for your lawn.
On the horizon: In search of a more sustainable grass
These are exciting times for sustainable lawn care in Minnesota. A $2.1 million dollar USDA grant was recently awarded to the University of Minnesota's Turfgrass Program for the improvement of fine fescues. Dr. Eric Watkins, a professor at the University of Minnesota, is the principle investigator on this project, which is a collaboration with Rutgers University and the University of Wisconsin-Madison. Intentions for this research include changing consumer habits, as well as improving the genetics of these low maintenance species. Please follow the links below for more information:
Jeffrey Hahn, Asst. Extension Entomologist
Termites are present in Minnesota but they are not common. They are found in southern Minnesota up to about the Twin Cities area and very rarely discovered, if ever, in central and northern Minnesota. Minnesota's native termites are subterranean termites, Reticulitermes spp. They maintain colonies in the ground and attack wood that is contact with the soil. You rarely see the termites themselves because the bulk of them stay inside the colony while those that travel outside of it move about in mud tubes they construct so they can maintain the proper temperature and humidity they need to survive.
That is why the discovery of winged termites in a home in Minneapolis during September was so interesting and unusual. First, when termites swarm, i.e. winged forms leave the nest en masse, they do so in the spring (and this is very rarely seen in Minnesota). Even more interesting was when the termites were examined more closely, they were identified not as the local subterranean termites but as drywood termites. This group of termites is not native to Minnesota but is most commonly found along the costal areas of the southern U.S. from North Carolina to California.
At first, just a single winged termite was found at a window at this home. Shortly after that, about 100 were found behind a couch. In the next couple of weeks, dozens more were found either behind or under the couch. The resident had owned this piece of furniture for 14 years. She had purchased it in Minnesota and never lived outside of the upper Midwest with it. The resident had never received any items mailed from areas where drywood termites are native nor had she ever noticed termites or sawdust in her home before, especially around the couch.
This brought up several excellent questions: where did the termites come from; how long have they been in the couch; and have they spread into other areas of the house? Information about drywood termite biology helped to answer these questions.
Although the couch had never traveled to any drywood termite endemic areas after the homeowner bought it, it undoubtedly was built and/or stored in a warehouse somewhere in the south where these termites are native. It was there that the couch became infested. You wouldn't normally think that insects could infest a piece of furniture for 14 years without their presence being noticed but drywood termite colonies grow very slowly and it isn't unusual for them to take that long before they are mature enough to produce new queens. So it is extremely likely that the termites were in the couch when it was bought and had been in the furniture during that entire time the resident owned it. Because the termites were confined to the couch, they did not spread to other areas in the house.
Fortunately for the homeowner, the only necessary control was to remove the couch from her home. It was taken away by a local pest management company, heat treated to kill the termites, and then properly disposed of. All's well that ends well.
Michelle Grabowski, UMN Extension Educator
University of Minnesota researchers Dr. Ben Lockhart and Dimitre Mollov have identified a new disease of spirea in Minnesota. Spireas are common landscape shrubs grown for their delicate foliage and summer flowers. The new disease, known as spirea stunt, causes plants to produce abnormally small leaves, that may be discolored yellow to reddish purple. Small discolored leaves grow only on clumps of weak branches known as witches' brooms. As a result, infected plants have one to many pom-pom like clumps of leaves and branches. The whole plant may be stunted and many infected plants do not survive the winter.
Spirea stunt disease is caused by a phytoplasma, a tiny bacteria that lives within the vascular system of infected plants. Dr. Lockhart determined that the phytoplasma infecting spirea in Minnesota belongs to the X-disease group and is related to similar pathogens that cause witches' brooms and stunting in blueberry, prunus and other shrubs. Little is known about the spirea stunt phytoplasma at this point. It is likely that this pathogen is transferred from plant to plant by leafhoppers or through plant propagation.
Once a plant is infected with spirea stunt phytoplasma, the pathogen spreads throughout the entire plant. There is no way to cure infected plants. Gardeners should remove shrubs infected with the spirea stunt phytoplasma as soon as possible.
Karl Foord - Extension Educator, Horticulture
Click on the link to see the video with host Dr. Mary Meyer, Professor of Horticulture