You Are Here: Management Updates 2002 Archive April 1, 2002

Date: April 1, 2002
Category: Insects
Subject: The Grubs are Coming! The Grubs are Coming!

We have had numerous telephone inquiries about grub damage within the past week, and I just collected some "fat and sassy" grubs on the Amherst campus this afternoon. Many of the grubs I collected were European chafers, a rather unexpected development. (European chafers had not been reported in Franklin or Hampshire county before, so now we have a new "hot spot".)

European chafer grubs are invariably the first species to return to the root zone to feed in the spring, and in some parts of southeastern Masschusetts, they have been feeding for a couple weeks already. Other turf managers are just beginning to see feeding damage, which tends to be most visible in areas where turf has been thinned from other problems - drought stress last year, heavy weed incroachment, or whatever. In addition, Japanese beetle and oriental beetle grubs are just beginning to resume feeding in some warmer locations (e.g., south-facing slopes).

DO NOT USE MERIT to try to control these spring grubs. The product does not work fast enough and studies conducted throughout the northeastern U.S. confirm that Merit has no measurable effect on spring grubs. Similarly, Mach 2 will not work very well on spring grubs either, primarily because it affects the ability of the grub to molt, and grubs have already reached their final stage.

There are virtually no turf insecticides available any longer that have "intermediate" characteristics, so the only reliable alternative for managing spring grub infestations would be trichlorfon, sold as Dylox or Proxol. This product will begin to work against grubs within one or two days after application but will only remain active for seven to ten days. In general we encourage turf managers to delay application until the soil moisture is around 50 F, but if the weather is going to be mild for several days, you MIGHT get away with applications sooner. No guarantees! As always, water the application thoroughly and be sure the water pH is well below 8.5, to avoid breakdown in the tank.

As always, if you are able to collect about 50 grubs and send them to us, we would be happy to identify the species of each individual grub. This information would help us to continue to fill in our knowledge of where each species occurs. Call my lab (413-545-0268) to get suggestions on how best to package the grubs, to get them to me safely and to keep the postal workers happy. Thanks for your help!

Submitted by: Dr. Pat Vittum