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Springtime Grub Issues

May 9, 2010

I was wondering if anyone else out there is experiencing grub problems this spring. We have had some digging for about 2 weeks now. We examined the turf to find numerous grubs like you would in the fall. I suspect that the amount of grubs might be attributed to the Japanese beetles that we experienced in mass numbers last year for the first time. I would be interested to hear from anyone that is or has experienced this problem before.

PS caught my first coon last night…..

Randy Moeller
Golf Course Supervisor
City of Muscatine, Iowa 52761


Japanese Beetle Update

July 2, 2009

The first reports of Japanese beetles have been received. Bob Dodds the Lee County Extension Director and incoming Region 20* Extension Education Director reported a few Japanese beetles in his orchard on June 22. Duane Gissel, Extension Horticulturist in Scott County reported the first sighting of JB on the morning of June 29, and by that afternoon was flooded with calls from clients. Most reports were from areas where JB has more recently arrived and residents are not familiar with the pest (Blue Grass and the western parts of Davenport, and Eldridge).

The current, known distribution of JB in Iowa includes 38 counties (picture on right). The first issue with Japanese beetles will be the feeding by the adults on foliage, flowers and fruit. Linden tree leaves are one of the favorite foods of the adult beetles. See

Defoliation is usually not fatal to otherwise healthy trees. We usually don't know what stresses are occurring so there is no easy way to predict the tree's response to defoliation. Treating grubs in the turfgrass does not impact the beetle populations on the tree the following year. There are way more places for grubs to develop in the soil than can be treated, and the relatively small amount of the total population that is treated does not impact the overall population.

In addition to spraying trees two or more times with insecticide for contact control of Japanese beetles, many landscape maintenance workers are reporting good success using systemic insecticides, applied to the soil around the base of the tree at the start of the beetle appearance. The insecticide moves upward and into the leaves and kills the beetles as they feed. Some injury still occurs but less than if the tree is not treated. See

(*NOTE: For more information on the ISU Extension Restructuring see our web site at

Donald Lewis
Extension Entomologist
104 Insectary Building
Iowa State University
Ames IA 50011 USA


Japanese Beetle - Reported Distribution

February 3, 2010

By the end of 2009 the Japanese beetle had been reported in 46 counties within the state of Iowa. The beetle is still primarily an eastern Iowa pest with a smattering of reports in the western half of the state. The updated distribution map is above.

Please keep us in mind next summer and send specimens or photographs from counties with no reports.

Thanks. Donald Lewis, Extension Entomologist


Japanese Beetle Activity on the Rise

July 18, 2011
Adult Japanese beetles burrowing into a golf course putting green.

The number of adult Japanese beetles has exploded the last couple of weeks. Once confined to the northeastern region of the country, this destructive insect has become a permanent part of the Midwestern landscape. This pest has continued its trek west across the country since being introduced into the U.S. from the Orient. Japanese beeltes were first reported in Iowa in 1994 and have gone on to inhabit approximately half of the counties in the state.

The Japanese beetle is one of the white grubs that includes the May and June beetle, masked chafer, green June beetle, European chafer, Asiatic garden beetle, Oriental beetle, and black turfgrass ataenius. The adult beetles can be identified by their green and bronze metallic head and shell and by the white tufts of hair that run along their abdomen. The larval stage must be identified by their raster pattern.

As with all white grubs, the Japanese Beetle larvae feed on the roots of grass plants just below the soil surface. Injury first often appears as drought that fails to respond favorably to irrigation. Each year the adult beetles emerge from the soil and begin mating and laying their eggs. This is the period we are currently experiencing. The eggs hatch in 2-3 weeks and the larvae begin feeding. Feeding can continue through the fall up until the first frost. Injury can also occur in the spring but is usually less severe due to the vigorous growth of cool-season grasses.

This particular grub species is somewhat unique in that the adult beetles also are significant pests of a wide range of ornamental plants. Japanese beetles feeding on leaf tissue leave a skeleton framework of veins following damage. Damage typically occurs at the top of the tree and works downward. Below is a picture of a Linden tree that is under attack from Japanese beetles.

Adult Japanese beetles feeding on a Linden tree.  The beetles usually start feeding at the top of the tree and work their way down.

Monitoring for white grubs can give you an indication of the severity of damage you may be able to expect. Sites with heavy beetle infestation in the summer months are likely incur grub damage during the fall months. Also, be sure to watch areas that have been damaged in the past as grubs often reinfest the same areas.

There are a number of insecticides on the market that are effective at controlling white grub species. The key to effective control is proper timing and placement of the products. Products applied preventatively or curatively are more effective against the grubs when they are small.

Regardless of the timing of the application, it is essential that the product be effectively watered in. Using nozzles that produce larger droplet sizes will help place the product further down in the canopy. Irrigation is normally recommended to help move the product down below the thatch layer and into the soil where the product will be most effective.

Based on the number of adults we are seeing we could be set for significant damage this fall. Monitoring for adult beetle activity is a great tool for those of who haven’t treated and are trying to decide what to do. The margin for error appears as if it will be quite slim as the turf will already be experience summer decline as we move through a week with high environmental stress.

Let us know what you’re seeing out there.

Marcus Jones
Assistant Scientist





March 17, 2014

Here are three more bulletins from Mary Broadfoot.  These were prepared as a special project in the advanced turf course, Hort 451.  Three bulletins on turf diseases were posted on March 13, 2014.  These three are on insects.  Three more on weeds will follow later.

 Japanese Beetle

Bluegrass Billbug

Chinch Bugs





July 1, 2013

I received information on the first sightings of Japanese beetles for the 2013 season over the weekend.  Larry Ginger of American Lawn Care reported a sighting in Ames from  June 27.  Dr. Donald Lewis, the turf entomologist from Iowa State also reports a sighting from June 26.  I have not seen any yet myself, although I have been watching.  I am planning a trial on the control of this insect on Roses that I will not be able to begin for a few days.

Let me know if others of you are seeing them.  Send pictures if you have them.

Larry reports that he has had good luck controlling them on landscape plants with a combination of Bisect for quick knock-down and Zylam for 30 day control.  Any other information on control would also be useful.

 Here is one of my photos of an adult form a couple of years ago.  They are about one half inch in length. 

Japanese Bettle



July 23, 2012

A common question the last two weeks has been "What happened to the lindens?".  The little leaf linden trees (Tilia cordata) seem to be dying from the top down.  Many of them look really bad this season.  The problem is the Japanese Beetle.  They seem to like to feed on this tree in preference to almost anything else in the landscape.

I did not realize how bad the problem was this year, until I drove down Airport Road in Ames this morning.  There are many 10 to 20 year old lindens along this road and they have been hit severely by Japanese Beetle feeding.  The damage does start at the top and then they move progressively down until they have nearly stripped the tree of foliage.  This does not seem to kill them, but it cannot be good for them, particularly with as much moisture and high temperature stress as we are getting this year.

The Japanese Beetle is a relatively new arrival here.  Up to about 5 or 6 years ago, we considered them to be an eastern pest.  But they have moved here in large numbers in the past few years.  This is by far the worst damage that I have seen here in Ames.

You can spray for them when they are actively feeding, although most people do not.  You can also use an imadocloprid (Merit) drench before they show up, although I have not had much luck with this treatment on my own linden.

The little leaf linden has been a highly desirable landscape plant in past years, but if this type of damage continues, they may lose some of their popularity.

Here are the pictures I took this morning.
Linden Tree Damage

Linden Tree Damage

Here are the culprits responsible for the damage.

Japanese Bettles



July 2, 2012

I was in Norway and Switzerland last week for some professional meetings and was not able to post more information about the Japanese Beetles showing up in Central Iowa.  During that time, I received several e-mails about beetles.  They showed up in large numbers in the last week of June.

The first picture is from Nick May, Manager of TruGreen in Ankeny.  It shows severe feeding damage on oak.

The second one from Dan Strey at the research station.  We are seeing large numbers of adults this week.



Japanese Bettle


The final picture is from a rose study next to the turf research area.  I took this today, July 2.








June 22, 2012

Here is a post from Aaron Loan of Bluegrass enterprises in Cedar Rapids.  They just started seeing the Japanese Beetles as well.  I still have not seen any here.

You can see a picture on the facebook site below:

From Aaron:

We have them at our place.  Just uploaded a pic on our facebook page:


Aaron A. Loan
Blue Grass Enterprises, Inc.
3965 C Ave Ext.
PO Box 335
Alburnett, IA 52202
P. 319-842-2165
F. 319-842-2173



June 21, 2012

I have been watching for Japanese Beetles in Ames because we are doing some research on them this year.  I have not seen any.  Three days ago, I got a call from a former student in Chicago, Brock Bollivar, saying that they had very high populations of adults there.  Then today, I got the following two pictures from T.J. Brewer at the Burlington Bees stadium in Burlington (on the Mississippi).  They showed up this morning in high numbers.  They do seem to show up from east to west, so I'll bet we will see them in central Iowa soon.  If any of you from the eastern part of the state see them this week, let me know.  Take some pictures and I'll post them.

Pictures From T.J. Brewer.  The miserable little devils are breeding and getting ready to lay eggs.