Wednesday, August 31, 2011


Nick Christians
August 31, 2011

Those of you who have been around since the 90's will remember a major outbreak of Gray Leaf Spot on perennial ryegrass in 1998. This disease is caused by the fungi Pyricularia grisea. It seems to selectively hit perennial rye. Under the right conditions, it can be more devastating than Pythium blight. Like Pythium, it can kill large areas of turf over night.

In 1998, it wiped out perennial rye from Chicago to the Rocky Mountains. It was particularly hard on ryegrass golf course fairways and sports fields.

The conditions that set it off in 1998 were unusually high temperatures around Labor Day. We have not seen a major outbreak of this disease in 13 years, but tomorrow it is predicted to reach near 100 F. That is very hot for Iowa in September. If you have perennial rye that has not been treated with a fungicide, you may wan to be on the look out for this problem. Banner/Daconil was particularly effective against Gray Leaf spot in the 1998 outbreak, but there are other materials labeled for it as well. Check the label before you spray.

The pictures below were taken in 1998 on Willow Creek Golf Course in Des Moines. The dead grass is perennial rye. The only living grass is Kentucy bluegrass that was intermingled in the fairway and some patches had been used to sod around some of the heads.

Let me know if any of you see this in the next few days. Send some pictures if you do.

Thursday, August 25, 2011


Nick Christians
August 25, 2011

The new greenhouses are now ready for use. If any of you would like to attend the dedication, come to campus on Sept. 3.

Jeffery Iles
Chair, Department of Horticulture

Gregory L. Geoffroy
President, Iowa State University

Wendy Wintersteen
Endowed Dean, College of
Agriculture and Life Sciences

Dwight Hughes
B.S. 1970 Horticulture
Cedar Rapids, Iowa

Winston Beck
Senior Horticulture Major
Jeffery Iles
Following the dedication ceremony, tours of the
Greenhouse Complex will be available.
Horticulture Teaching & Research
Greenhouse Complex

Saturday, September 3, 2011 at 2 p.m

The new $4 million teaching and research greenhouse complex on central campus replaces the original horticulture greenhouses built in 1913. It extends along the south side of Horticulture Hall, home of the department of horticulture. The facility includes space-efficient teaching and research areas equipped with state-of-the-art environmental control and innovative plant production systems.

The greenhouse complex is partitioned into several compartments dedicated to research, teaching and student club activities. A computerized control system monitors and regulates environmental parameters such as temperature, humidity, and light intensity in each greenhouse compartment, providing optimal conditions for plant growth and a first-rate experience for students and researchers.

The project was made possible through private donations and funding from Iowa State University.

Architectural Firm: Baldwin White Architects, Tom Baldwin and Dusica Stankovic
Engineer: Howard R. Green Company
Civil Engineer: Snyder and Associates
Structural Engineer: Raker Rhodes Engineering
General Contractor: Story Construction
Subcontractors: Albert J. Lauer Greenhouse, Inc., Jaspering Electric,
L.A. Fulton & Sons
Construction and Project Management
Project Manager – Mark Huss
Construction Manager – Lynn Burnett
Department of Horticulture – Jeffery Iles, chair;
Richard Gladon and Pete Lawlor
Horticulture Teaching & Research
Greenhouse Complex

Wednesday, August 17, 2011

More Ascochyta Disease Across the State

Dave Minner, ISU Extension Turfgrass Specialist
Mark Gleason, ISU Extension Plant Pathologist
Erika Saalau, ISU Plant Diagnostic Clinic

For the second year in a row Ascochyta has hit lawns, athletic fields, and golf course turf. Ascochyta leaf blight is a grass fungus that causes a rapid straw to bleached appearance of the leaves primarily on Kentucky bluegrass and to a lesser extent on perennial ryegrass and tall fescue. The damaged lawns started showing up around the first of June and out breaks have been occurring all summer long. Some of the more severely damaged areas may require 3 or 4 weeks of good growing conditions to fully recover.

The damaged areas seem to occur very quickly; one day the grass appears fine and the next there is bleached tan grass everywhere and most noticeably where the mower tires track. In fact, to those unfamiliar with this problem they think that someone has damaged the lawn with a pesticide or fertilizer application. The Ascochyta related problems I am seeing have nothing to do with product applications. The fungus likes to grow during wet conditions favored by lots of rain or over irrigation. Infectious spores are everywhere throughout the lawn and with a sudden increase in hot temperatures they rapidly infect the stressed grass.

Tire tracks show up because the tires spread the spores and also cause just enough abrasion stress for the fungus to enter the plan tissue. Look for bleached leaf tips that are collapsed. It looks devastating because the top part of the plant is severely damaged but the crowns and lower stems are seldom killed. The attacks are so haphazard that it is impossible to give a good recommendation as to when to avoid mowing but in general raising the mowing height and mowing less frequently will reduce your chance of experiencing a mowing track incidence. It is interesting to note that Ascochyta blight in home lawns only occurs in full sun areas and it stops where the shaded lawn has less heat stress.

The damage at first appears very dramatic but the good news is to simply be patient because most of the damage is on the leaves while the crowns and roots of the plant are not damaged. As the plants continue to grow and after about a month of normal mowing the damaged leaf tips will be removed and the lawn will return to normal.
Normally we don’t recommend a preventative fungicide because it occurs too haphazardly and a curative fungicide doesn’t help after the leaf tissue is blighted. However, if you have experienced this in the same lawns and athletic fields for two years in a row you may want to consider a single preventative application of a fungicide next year from mid May to mid June.

Much of the turf I have sampled this summer has been confirmed to be Ascochyta by laboratory identification of spores. Like most of you old timers over the years I have observed tire tracking that we have assumed to be related to hot or dry conditions. Laboratory identification of the pathogen is the best way to determine if it was related to Ascochyta. Next year we will be conducting research with fungicides, moisture conditions, and wheel pressure to determine what is causing the tire tracking; is it Ascochyta or is it simply high temperature or low moisture stress. I think most of the blighting and wheel tracking we observed in June and July were associated with Ascochyta. To a lesser degree we may have also observed some wheel tracking from high temperature/drought stress.

Areas that have been severely injured can be recovered by dethatching, hollow tine aerification, and reseeding in September.

Here are some of the Ascochyta injured lawns that we have observed in Iowa during the summer of 2011.

Ascochyta in mower streaks on athletic field in Iowa City, IA.  Picture taken 7/15/11.

Close up of Ascochyta symptoms on Kentucky bluegrass.  Note the bleached leaf tips and banding of leaf blades.  These symptoms are different from dollar spot that has leaf lesions with bleached centers and brown boarders.

Obvious tire tracks from mower associated with Ascochyta in Ankeny, IA.  Picture taken 5/20/11.

Picture in Ames, IA showing wheel and deck tracks associated with Ascochyta.  Picture taken 6/16/11.

Ascochyta can also injure lawns without leaving the mowing tracks.  Picture taken in Ames, IA 6/16/11.

Wheel track lawn injury from Ascochyta but notice that the tracks are not present in the shaded areas where the grass has less heat stress.  The Ascochyta spores may be present everywhere but it usually requires a period of sudden heat or drought before symptoms appear.  Picture taken 6/1711 Ames, IA.

More Ascochyta mower tracks from Parkersburg, IA.

Darker green lawn (bottom) with higher nitrogen fertility shows more Ascochyta injury than lower fertility lawn (top).  Nitrogen applied at 2 to 4 lbs N/1000sqft/yr is suggested to maintain healthy lawn growth.

Low maintenance (no fertilizer and no irrigation) Kentucky bluegrass along roadside showing mower tracks with Ascochyta injury.  Even though high nitrogen can cause lush growth that increases infection in this case turf was injured in a low nitrogen situation.

Mowing tracks on golf course fairway.  Injury occurred during a period when turf was not wilted or under low moisture stress.  Grass died in lower wet areas but recovered on sloped areas.  Also notice that the tracks stop at higher cut rough in front of sand trap.  We will be conducting research next summer to discern what is Ascochyta related and what may be related to high temperature or drought stress wheel tracking.  Picture taken 7-20-11 Waverly, IA.