You Are Here: Management Updates 2005 Archive August 30, 2005

Date: August 30, 2005
Category: Insects
Subject: Annual Bluegrass (Hyperodes) Weevil, White Grubs

The good news
The good news is that annual bluegrass (Hyperodes) weevil activity is declining rapidly. Areas that had high populations earlier in the year are seeing fewer insects, and the damage is finally dropping off. It is safe to assume that any adults we see now will begin preparations for winter. They may take their sweet time moving off to their overwintering sites, but damage from adults is truly negligible. (They sometimes nibble notches in the grass blades, but these sections are well above the growing point and do not compromise the health of the plant.) So you can finally have a sigh of relief - those who still have larvae feeding will see less and less damage from those larvae as the temperatures continue to cool and those larvae develop into new adults.

So hang in there. We will be working this winter to prepare a series of guidelines for managing the insect next year, taking into account that there appear to be pockets of resistance to pyrethroids in certain parts of the Northeast. Don't panic yet - we do have some options that should help us out!

The bad news
The bad news is that white grubs are becoming increasingly active. When we collected plugs, ostensibly looking for Hyperodes weevils, what we got was oriental beetle larvae!!! We have been sampling for grubs in several areas throughout southern New England, and find that grubs in several locations are fairly well developed. In general we are seeing late first instars and very healthy second instars (medium sized larvae).

The rains that are currently falling will mask damage for a while, but it would be wise for turf managers to get out and take a look now. It appears that most eggs have hatched by now, and grub activity will increase as the little monsters continue to eat and grow larger. The bigger they are, the more difficult it is to manage them, so look now and determine whether you have areas that are under attack.

Rescue treatment options at this point include (in no particular order):

1. trichlorfon (Dylox™) - Very fast acting, will kill what it is going to kill
   within one to three days. Dylox™ is very mobile, so do not use it on sandy soils
   or near surface water or before rain is forecast. It is very sensitive to high
   pH. Dylox™ cannot be used on school grounds that come under the auspices of the
   School IPM laws in Massachusetts.
   
2. carbaryl (Sevin™) - Relatively fast acting, very inconsistent. Sometimes it
   works, and sometimes it doesn't! Sevin™ is very toxic to bees and wasps, so do
   not use near plants that are flowering or where bees or wasps are foraging.
   
3. chlothianidin (Arena™) - This is a relatively new compound related to Merit™. The
   manufacturer claims that it can be used as a rescue treatment, but we have not
   had the material in field trials to test that concept. So let the buyer beware.
   
4. halofenozide (Mach 2™) - Again the manufacturers claim this product can be used
   later in the season than Merit™. But halofenozide interferes with the grub''s
   ability to molt. If grubs have already molted to the third instar (which many
   will do soon), no benefit would be gained from applying Mach 2™. Personally I
   think it is too late this year.
   
5. Nematodes, specifically Heterorhabditis bacteriophora - These nematodes are
   available under several trade names and sometimes reduce grub populations. See
   messages in the archives from spring 2004, where we discussed the benefits and
   drawbacks of using nematodes. Once grubs approach full size, it is more
   difficult for the nematodes to be effective. So we are running out of time in
   many locations. Also note that Albrecht Koppenhoffer (my colleague at Rutgers
   University) reports that HB nematodes are more likely to be effective against
   Japanese beetle grubs and much less likely to be effective against the other
   species many of you are dealing with.
   
   Remember, that any grub treatment must be watered in thoroughly.

Submitted by: Dr. Pat Vittum

DISCLAIMER - As always, it is the responsibility of the applicator to verify the registration status of any pesticide BEFORE applying it. Different states have different regulations as well. The author and the University of Massachusetts are not liable for any consequences of any pesticide "recommendations". Mention of any trade name is not to be considered endorsement of a product.

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