County Spraying Naled — At the Wrong Time of Day?

Miami-Dade is aerial spraying a pesticide banned in the EU to control potentially Zika-infested mosquitoes:

Vasquez, of the county’s mosquito control unit, also said that while initial spraying had reduced mosquitoes, the number had started to rise again with recent heavy rain. The county plans to conduct eight aerial treatments altogether, four with an insecticide called Naled and four with BTI, an organic larvicide to attack eggs. The area has been divided into sectors, with nine teams doing door-to-door inspections in search of breeding mosquitoes, he said.

Zika Virus: Count rises in Miami with another case.

There are two problems here. First, Naled was banned by the European Union in 2012 because the risk to humans and to the environment was deemed unacceptable.

The US Air Force also recently sprayed Naled, aka Dibron, in an uspecified wide area around the Homestead Air Force Base (including residential areas) “to improve working conditions and lower the risk of vector-borne illnesses to individuals who work and live at Homestead Air Reserve Base and the surrounding Miami-Dade County.”

There’s also a question of timing. I assume that in general it’s better to do aerial spraying when fewer people are on the street so as not to get the spray on people. (Seems logical, but if any readers are expert in pesticides, please correct me if I’m wrong about that.) But when the Air Force sprayed, it did it in the evening when the mosquitoes are most likely to be flying: “Since it is an aerial spray, most mosquitoes have to be in the air to contact the material, that is why we do it so close to evening when mosquito populations are coming out of their hiding spaces” said Lt. Col. Karl Haagsma, entomologist for 910th Airlift Wing.

In contrast, the Miami-Dade spraying started early in the morning and kept going through rush hour:

On Wednesday, a low-flying plane misted the area with a nontoxic larvicide intended to kill mosquito eggs, Casey said. But a flight that was scheduled to fly at 6:30 a.m. was still flying overhead at 10 a.m., angering business owners already on edge about scaring away customers.

I’m no biologist, but isn’t this the worst of both worlds: spraying when all the humans are up and about, but not the mosquitoes?

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One Response to County Spraying Naled — At the Wrong Time of Day?

  1. K.R. Thompson says:

    Aedes mosquitos (the vector for Zika) bite at all periods of the day (they are sometimes called day biters but they bite at other times as well). Because of that, spraying during the day and evening is not unusual in controlling Aedes species. Also, as you mentioned, one spraying period targeted adults while the other targeted eggs and larvae. There is nothing wrong or illogical about the spraying listed, the periods were done to specifically target the biology of the species of concern.

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