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


Nick Christians Professor

Nick Christians, Ph.D. – University professor of turfgrass management, Iowa State University, Department of Horticulture, Ames, IA, and adjunct faculty, Department of Agronomy, Iowa State University, Ames, IA. Dr. Christians received his B.S. from the Colorado State University ...