You Are Here: Management Updates 2003 Archive July 2, 2003

Date: July 2, 2003
Category: Insects
Subject: Hyperodes on the Move!

My telephone has been ringing off the hook this week with golf course superintendents reporting damage from the annual bluegrass weevil (Hyperodes weevil). Calls have come from southern New Jersey up through coastal Maine, with every point in between also represented.

Here is the deal as I see it. As we mentioned earlier, this year is particularly confusing because egg-laying took place over a much longer period during the spring than normal. As a result we are not seeing the usual "spike" of activity, where most of the insects are in the same stage of development at the same time. Instead we are getting samples with tiny larvae, middle-sized larvae, and large larvae, as well as pupae and adults - all in the same plug.

There are two basic approaches for controlling the insect. One is to target adults just after they emerge and before they have a chance to lay eggs. In this case you should use a material that is relatively insoluble (and therefore immobile), so it will stay in the thatch where the adults are active. Options include chlorpyrifos (Dursban™) or any of the synthetic pyrethroids labeled for golf courses, including such things as bifenthrin (Talstar™), cyfluthrin (Tempo™), lambda-cyhalothrin (Battle, Scimitar™), or deltamethrin (Deltagard™). In this case you should water lightly (one or two passes of the irrigation head), to get the material off the leaf blades and into the thatch.

The second approach is to manage the damage that is done by the larvae. Most of the products currently labeled against annual bluegrass weevils target adults. As far as I know, there are no products labeled against annual bluegrass weevil larvae specifically at this time. However, we have found that on occasion some relief can be obtained by applying trichlorfon (Dylox™). This suggestion should not be construed as a recommendation because the supporting data have not been collected, but anecdotal reports and personal observation suggest that some suppression of the larval activity may occur in some situations. The situations in which we have observed suppression have been when applications were made at the white grub rate. (In the situations where trichlorfon appeared to suppress larval populations, the applications were made when small larvae were present and the area was watered in lightly.)

Note that annual bluegrass weevils are not on the trichlorfon label. In states where only the site must be on the label (e.g., Massachusetts), you can make the application legally but keep in mind that it may or may not work. You will have no legal recourse with the manufacturer if you do not achieve control (because the company has made no claims of control). In states where both the site and the pest must be on the label (e.g., New York), this approach cannot be used legally unless you are in a situation where other pests that are on the label are also present. Also note that trichlorfon is not available in Maine and is not legal under any circumstances in that state.

Finally, it will be really important to keep track of the stage of development of the weevils throughout the summer. If you have about an equal number of pupae and larvae, you might spot treat with trichlorfon if that is an option for you (see above) in the areas where you see the wilting, and plan to return with an adult material about two weeks later. (The waiting game is a hard one to play, but you must give the pupae a chance to develop to adults. Remember that pupae are not susceptible to insecticides.) If you have mostly pupae in your samples, do not waste your time or your money - the damage has been done for that generation and you should target the adults about a week later.

Right now it appears that for many superintendents in central, coastal, or northern New England, the target date for treating the adults of the next generation will be between 10 and 20 July. The target date for the metropolitan New York area will probably be just a bit earlier - the week of 7 July.

There is an easy way to sample for annual bluegrass weevils. Nancy Consolie, a technician in Dan Peck's laboratory at the New York State Agricultural Experiment Station in Geneva, developed a salt soak. Collect a turf sample and trim it so there is no more than an inch of soil along with the roots, thatch, and blades. Put the sample in a container big enough to submerge the entire sample. If you take a cup cutter plug, cut it into four sections and throw the whole thing in one container. Mix 3/4 of a cup of table salt in a quart of luke warm water. (This will result in a saturated solution so slosh it around really thoroughly.) Then pour the salty mix over the plug so the plug is completely submerged (with at least a half inch of water above the top of the plug). Most larvae will float to the surface within about an hour. This technique will enable you to determine what sizes of larvae are present, and help you sort out your situation.

Larvae are cream colored with brown heads and no legs. The smallest larvae are the size of a Poa annua seed. The largest ones are about the size of a grain of rice. Pupae are cream colored and kind of diamond-shaped. They do not have brown heads.

Good luck!!!

- Submitted by: Dr. Pat Vittum