Cause and effect

There has been a lively recent discussion about mosquito control on the Front Porch Forum for Salisbury, Leicester, Ripton, and Goshen. A common observation made by local residents is that mosquitoes were once a terrible problem in the BLSG district, but since the BLSG-administered roadside spraying began years ago, the mosquitoes are not nearly as bad. The implication is that roadside spraying of chemical pesticides has been responsible for a long-term easing of the mosquito problem.

Evidence from this spring does not support that argument. The last time BLSG did roadside spraying anywhere in the district was June 8 which was 11 days ago when five routes were sprayed.  Nineteen days ago, another five routes were sprayed, and 21 days ago seven different routes were sprayed.  So as of today, all of the routes in the district have gone for at least 11 to 21 days without being sprayed.

The spray mist stops killing mosquitoes a few hours after the truck drives by. There is little or no long-term effect of this type of spraying because mosquitoes that weren’t flying or mosquitoes a couple hundred feet from the road are not affected. About 90% of the district is more than a couple hundred feet from a spray route, so most mosquitoes never encounter the pesticide. And it does little to stop new eggs from being laid or new larvae from hatching.

If it were the roadside spraying that keeps the mosquito population down and the district has gone 11 to 21 days without spraying, the mosquitoes should be as thick as they were back in the bad old days. But they are not. The mosquitoes are like they are most years in June–a minor nuisance at dusk and dawn just like they typically are everywhere else in Vermont this time of year.

If there is a long-term improvement in the mosquito situation it should not be attributed to roadside spraying of chemical pesticides. The cause might be natural variation in mosquito populations, or it might be the state-funded program of aerial larvicide application. That program prevents mosquito larvae from hatching into adults over thousands of acres of breeding areas and can have a substantial and long-term effect on the number of mosquitoes that residents experience. Our neighboring towns in the Lemon Fair Insect Control District use only larvicides to control mosquitoes.

The BLSG administration recently learned that they probably will not have enough money to apply the desired amount of larvicides during the next year. We should all be working to ensure that the Vermont Agency of Agriculture supplies adequate funding for this program. Unlike the chemicals sprayed along roads, the bacterial larvicides applied have trivial potential for health or environmental consequences.

The program of roadside spraying of chemical pesticides to kill adult mosquitoes is funded directly by the towns in the district. The last few weeks provide good evidence that this roadside spraying is not responsible for any long term or sustained reduction in the mosquito population. Select Board members in the towns of the BLSG district should think carefully about the tens of thousands of tax dollars being spent every year to repeatedly spray toxic chemical pesticides in residents’ front yards.  What evidence do you have that these dangerous chemicals aren’t doing more harm than good?

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