You Are Here: Management Updates 2000 Archive September 26, 2000

Date: September 26, 2000
Category: Insects
Subject: White Grubs

Based on what I have been seeing over the past couple weeks, I suspect some turf managers will experience significant damage from white grubs this fall. We have been lulled into complacency because the summer was so wet, and the grass grew well in most locations. Meanwhile Japanese beetle adults were not in evidence, certainly not in the levels we have seen in recent years. However, I have seen several sites in the past two weeks that are beginning to show weak areas where grubs are feeding actively and skunks or raccoons are foraging VERY actively.

My best guess is that grub development was delayed throughout the state, regardless of species, in part because air temperatures were unusually cool and in part because steady rainfall kept soil temperatures lower than normal. In fact we were still seeing Japanese beetle eggs in turf sites as recently as two weeks ago, VERY late!

Now the late-developing grubs are reaching second and third instars, and are getting large enough to cause noticeable damage in a variety of turf areas. Unfortunately it is also getting too late to do anything about them. So be prepared and monitor some of those areas where you always seem to find grubs. My guess is that they will be there!

In terms of options, the list is very limited at this point. For some of you, managing the damage will be the only choice - roll affected areas, provide irrigation if necessary to keep the grass growing, raise the mowing height if possible. It is really too late to use any insecticides, although some of you may opt to try a very fast acting and mobile material like Dylox or Proxol. Keep in mind that it is already at least two weeks later in the year than we normally like to see such insecticides being used, and that effectiveness will be compromised as soil temperatures begin to drop.

Good Luck!

- Submitted by: Dr. Pat Vittum