Monday, September 14, 2015


Nick Christians
Sept 14, 2015

Here is an update on the new sports turf research area at the Horticulture Research Station at Iowa state.  It is a time lapse from May 1 until the 2nd week of September.  Everything is now seeded and the new grass is coming in fast.  Dan was able to mow some of it this week.


If anyone would like to stop out and see it, let me know.

Friday, September 4, 2015

Football is here - and so are the white grubs?

With the air temperatures climbing back into the high 80’s and low 90’s, now will be a crucial time to monitor for white grubs.

The term “white grub” refers to a group of insects with a larval stage that damage turf. Subsurface feeding insects are of major concern in athletic fields because they feed on roots, cause turf to be easily dislodged, and result in poor footing. Know the life cycle of underground feeders such as grubs and anticipate when they may become a problem. The beginning of football season coincides with peak turf injury from white grubs. Masked chafers, Japanese beetles and May/June beetle are the most common grub species to attack Iowa athletic fields. Annual grubs such as masked chafers and Japanese beetles lay their eggs in the spring, and hatch in the summer. The larvae begin to feed on the root systems in August and these two species are commonly referred to as “fall grubs”, because a majority of damage occurs in the fall. 

The damage is best diagnosed by grasping the blades of the grass and lifting. This process is known as a “tug test”. The grass will break away at the roots. Another option is to shovel or spade a three sided 1 sq. ft. piece of sod about 3 inches deep. Slowly peel back the sod and expose the soil as was done in the picture below. 

Figure 1. Several white grubs feeding on athletic field in Fort Madison, IA. Picture courtesy of Cody Freeman.
Fall grubs that sever the root system do not necessarily kill the grass. If it is properly watered via irrigation or rainfall, it will recover. The drought stress following grub damage, kills the grass. With the warm temperatures in the foreseeable future, it is the most likely time to see damage across Iowa, especially if the rain switch suddenly turns off.  

Keep Dylox or another insecticide handy for preventative measures. It is important to remember that all products need to be watered in. Using nozzles that produce larger droplets will move the product further into the canopy. After application, irrigation or rainfall can help move the product down into the soil, where it can be most effective. 

Tuesday, August 25, 2015


Nick Christians
August 25, 2015

It is a common phenomenon on the golf course to have green footprints appear in mid summer, with brown grass surrounding the prints.  While this is a common problem on creeping bentgrass on golf course, I also had a couple of questions from people who had this occur on their Kentucky bluegrass lawn this summer.  The problem is mosquito spray that contain a chemical called DEET (N,N-diethyl-meta-toluamide)..  This material is a great mosquito repellent, but is deadly to grass.  The problem occurs when someone stands on the grass and spray their feet to protect themselves from mosquito bites.

This past summer, undergraduate research associate Zack Olinger, performed a demonstration on this problem for the annual field day in July.  He did this in conjunction with his supervisor at the research station, Dan Strey.

The following is his description of the project:

From Zack

The objectives of this demonstration were to show effects of commercial spray products on the turf, and the timeframe for recovery following damage. With so many products readily available in today’s market, I decided to try an aerosol bug spray, an all-natural bug spray, and sunscreen. My goal was to demonstrate the effects of direct application of these products on the turf. I used OFF! Deep Woods® (25% DEET), Bug Soother (Lemongrass Oil 0.5%), Coppertone Sport High Performance® 30 SPF Broad Spectrum (Octisalate 5%, Avobenzone 3%, Homosalate 10%, Octocrylene 10%). I set up a demonstration using 2’x2’ plots on Creeping Bentgrass, Agrostis stolonifera. The turf was mowed daily at .140”, the average height of many golf course greens. The application of the products were set-up in order to showcase results at the 2015 ITI Turfgrass Research Field Day on July 23, 2015. The Applications were made on July 9, 16, and 21. Below is a plot plan for the demonstration showing the application timing. Attached is also a record of daily weather and soil information during the course of the trial. I used an old pair of Nike Shoes and set them in the plot that the product was being applied to, then the product was sprayed evenly across the plot at a normal use rate resembling that used by the golfer. The plots were treated on their respective date and then observed for recovery from damage for several weeks.

Table of treatments with dates of application.

I found that the OFF! Deep Woods Bug Spray caused severe turf damage. The turf immediately shows signs of stress following application. The turf turned a dark purple (resembling the color of wilted grass) and then started to turn brown within 2-3 hours. By 24 hours after application the turf is damaged to the full extent. The turf took approximately 3 weeks to return to its original quality. Some spots in the plots never came back and would need to be reseeded or left to fill back in during the cooler weather of fall. 
The Bug Soother showed no adverse effects on the turf.  Immediately after application, the turf showed a shiny appearance that wore off after approximately 1 hour. The turf continued to live with no problems throughout the trial. The Sunscreen showed the same signs as the OFF! Deep Woods Bug Spray following application. The turf resembled the appearance of wilt for 3-4 hours and then started to brown out for 2 days until it reached the point of recovery. The sunscreen took approximately 8-10 days to return to its original quality. With all of the products there was a 98% recovery within 3 weeks. 
Most golfers  do not know about this problem.  Posting signs in the pro shop can help.  It may also be a good idea to provide a natural insect repellent at the counter so that they do not have to use the DEET product on the course.

Zack Olinger, (olinger@iastate.edu)
Dean Strey (dstrey@iastate.edu)

This is a a picture of the damage from the DEET product on August 22.  There is no damage from the other products on that date.

Pictures of damage from DEET product on Field Day, Aug. 23

 DEET Containing product.

Natural Bug repellent containing Lemon Grass oil.