You Are Here: Management Updates 2002 Archive May 30, 2002

Date: May 30, 2002
Category: Insects
Subject: Hyperodes Weevils, Armyworms, Grubs

Annual bluegrass weevils (primarily a golf course problem):
We have been collecting turf samples from Westchester County, New York, throughout the spring to track the development of the annual bluegrass weevil ('Hyperodes weevil'). Plugs from the week of 22 May had small and medium sized larvae, and we are beginning to get reports of the early wilt that often precedes wholescale weevil damage. Superintendents in southern New England should consider this as their "heads up" - annual bluegrass weevil larvae should start showing up on your courses this week, and you may expect to see some wilting during the first week of June, especially if the weather is warm and dry.

This year is shaping up as a very confusing one regarding the timing of insect development. We suspect that some of the adult weevils moved early in April, during the unseasonably warm weather, and others delayed their movement until later in May. As a result, I believe we will see a wider range of larval activity in June. In most years, most of the larvae are within a week of each other in their development in a given location, and a superintendent can kind of guess where they are heading. This year we are already seeing very small larvae, medium sized larvae, and nearly full grown larvae, all within a few inches of each other. So even if a superintendent applied a pyrethroid in April preventively, there may still be some larval damage in June from the "early birds" or the "laggards" that were not affected by the April application.

At this point there is really only one management strategy that can help in most cases. Once a superintendent notices larvae feeding in the usual hot spots, he or she can apply a fast-acting insecticide that does not get tied up in the thatch (in other words, don't use chlorpyrifos or a synthetic pyrethroid). Check the label and be sure the weevil is on the label and/or the site is labeled. Note that some turf managers are in areas where such products are not cleared for use, so read the label and be familiar with your own state regulations.

We will be tracking weather patterns and will post suggestions for follow-up preventive applications in late June or early July for people in the metropolitan New York area, slightly later for those in New England. The timing of these applications is based on a preliminary degree day system - but with the confusions of this season, our best guess may not be that helpful!

Armyworms:
We have received word that relatively heavy flights of armyworm moths were reported in central Ohio about ten days ago. We do not yet know whether those moths might have been blown eastward toward New England, but now would be a good time to start monitoring moth flights. Meanwhile we have not heard of any large numbers of moths in New Jersey or Delaware, which can be considered good news - both for the New Jerseyites and Delawarans and for New Englanders!

Grubs:
White grubs are winding down their feeding activity. We were digging on the Amherst campus this morning and encountered several pupae (presumably of European chafers), and last night I found adult asiatic garden beetles in a daylily bed in my back yard. So most grub damage should be diminishing now. Those who encountered severe damage may want to make an application of a preventive material in late June or July. Check previous management updates to review the best timing for each of the species -remember that applications for European chafers should be made a couple weeks earlier than for most of the other species.

- Submitted by: Dr. Pat Vittum