You Are Here: Management Updates 2000 Archive August 18, 2000

Date: August 18, 2000
Category: Insects
Subject: White Grubs, West Nile Virus

This summer is certainly one to remember - the continued cool and moist conditions have kept grass growing lushly in most locations, and may be giving turf managers a false sense of security with regards to insect activity. In particular, WHITE GRUBS are beginning to hatch in most locations and are feeding on turf roots. While the steady rain pattern has masked this activity, turf could start to show stress if the weather pattern changes and we enter a dry spell. In any case, those who have a history of white grub activity should start scouting now to determine where grubs are active this year.

The good news is that we are nearly through the period when we normally see damage from billbugs or chinchbugs, but according to the "grapevine", it has been a relatively quiet year. Again I suspect the insects were active in their usual haunts but the activity was masked by the nearly constant supply of moisture.

On an entirely separate note, however, some turf managers have been calling and asking whether they should be trying to control mosquitoes, in response to reports of WEST NILE VIRUS showing up in Massachusetts. The following observations are strictly my own and very conjectural, but are based on regular reports I receive from Cornell University. First, a few points:

1. West Nile virus is carried by a couple of species of mosquitoes, one of which (Aedes japonicus) feeds during the day and at dusk, while the other (a Culex species) feeds primarily at dusk.

2. Most northeastern states are conducting surveillance by collecting dead birds and determining whether they have the virus. The numbers of infected dead birds seems to be rising, and certainly there have been some birds found in eastern Massachusetts (primarily around Brookline), as well as in Rhode Island and Connecticut. However, it is difficult to sort out what percentage of the dead birds found contained the virus - reports tend to tell us only how many birds were infected, but was it 1% of the dead birds found or 45%?

3. Only a very low percentage of mosquitoes actually carries the virus, and only a small percentage of humans are infected as a result of bites from these mosquitoes.

4. The virus normally is most "active" in segments of the population who are considered to be at risk - the elderly, the very young, people with compromised immune systems.

So WHAT SHOULD WE BE DOING??? The current approach in areas that are on the periphery of disease activity is to stress common sense. Try to reduce mosquito activity by eliminating their breeding sites. While some people would read that sentence and begin to crank up the sprayers, a more environmentally sensitive approach might be to concentrate on areas where water accumulates - empty out the pools in the old tires, clean out the gutters, open up drainage in ditches, provide aeration in ponds.

Reduce the likelihood of mosquitoe bites - encourage workers or golfers to wear long sleeves (and long pants) and use repellents.

While the news media tend to focus on the highly visible aerial applications that are directed toward adult mosquito populations, turf managers may want to consider using materials that affect the larvae. There are at least a couple of non-chemical approaches (one of which is a strain of Bacillus thuringiensis) that should have a narrower impact on the aquatic environment than traditional insecticides. However, I am not familiar enough with the biology of the species in question, so I do not know whether it makes sense to treat the pools of water this late in the season.

The main point is, DON'T PANIC! While we may be dealing with West Nile virus for the next several years, it does not appear necessary to panic and throw all our weapons at mosquitoes - at least not yet!

- Submitted by: Dr. Pat Vittum