You Are Here: Management Updates 2002 Archive April 16, 2002

Date: April 16, 2002
Category: Insects
Subject: European Chafers on the Move

We have had reports of European chafer grub activity from several areas throughout the Northeast, including the Mid Coast region of Maine, the UMass campus in Amherst, Rockland County just north of New York City, and even some of the valley towns between Scranton and Allentown, Pennsylvania. While not all of these reports have included confirmation of grub species, we believe the European chafer is on the increase in many parts of the Northeast.

Why are we seeing European chafers in so many new locations?

European chafers are favored by dry conditions, and thrive in turf areas where soils are on the dry side. Many areas of the Northeast experienced reduced rainfall last fall, which favored European chafer growth and spread. The chafers have undoubtedly been in these areas for a year or two, but with the dry conditions in 2001, more chafer grubs survived than did the grubs of more moisture-sensitive species like the Japanese beetle. This pattern matches historical experience. European chafer "invasions" often occur the year after a hot and dry summer.

Why does the European chafer seem to cause more damage than its cousins (e.g., the Japanese beetle and oriental beetle)?

European chafers are slightly larger, so the grubs are larger when they complete their development. In general, larger grubs eat more! But even more importantly, European chafer grubs are much less sensitive to cold conditions, so they stay in the root zone feeding well into December, and return to the root zone to feed as early as late February. This means the period during which European chafers feed is about four weeks longer in the fall and four to six weeks longer in the spring.

What do I need to know about the European chafer life cycle?

The European chafer life cycle is very similar to that of the Japanese beetle, but in any given location, the chafer will complete its development about two weeks EARLIER than the Japanese beetle. So in southern New England, we can expect to see adults emerging in mid June, and egglaying will start in the last week of June or first week of July.

What can I do about the European chafer grubs I see rototilling my turf now (mid April)?

The only alternative we have for a quick knockdown of white grubs in the spring is trichlorfon (Dylox or Proxol). This is a fast-acting insecticide that will kill grubs within a day or two after application but will break down in the soil about a week after application. We suspect that Dylox (or Proxol) has limited effectiveness when soil temperatures are below 50 degrees, so early spring applications may not have been successful. Meanwhile European chafers are less vulnerable to insecticides than any of their "cousins", so a turf manager should not expect control to exceed 50 to 70%. But in many cases this will provide the necessary relief so you can keep up with managing the damage.

As with any grub insecticide application, be sure to WATER THE MATERIAL INTO THE SOIL, using at least 0.1 inch of irrigation. (Even more water would be beneficial, but may be difficult to achieve in the current situation.) And check the pH of the water, especially if making a liquid application. Dylox and Proxol are both sensitive to water with high pH, so if the pH is greater than 8.0, be sure to use an additive to drop the pH closer to neutral (7.0).

And finally, a correction - In a previous update, I mentioned that Dylox (or Proxol), Merit, and Mach 2 were the only insecticides avaiable that show activity against white grubs in field conditions. (The latter two are only appropriate to be used later in the season.) According to a Bayer representative, Oftanol (isofenphos) IS still available for use on turf through 2002. Bayer is supporting state registrations in all six New England states as well as New York state (and very possibly many more states, but I only asked about New England and New York), supporting the use of the flowable formulation of Oftanol. It would not be a suitable option for the spring grubs, but can be considered to treat grub-infested areas during the coming summer (probably late July or early August for areas that are primarily infested with European chafers, slightly later for other grub species).

- Submitted by: Dr. Pat Vittum