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Hey Joe: What's in That Mosquito Spray?

Q. I'm a longtime listener of your show (www.youbetyourgarden.org) and really appreciate all that I've learned from you. But now I have a problem. We have a small lot with gardens, including a vegetable garden (all-organic, composting, the whole bit). We also love wildlife and get a surprising number of birds and other animals. One of my favorite sounds in summer is crickets singing.

Enter the villain, or what I think is the villain. Our neighbor (who is a very nice woman), has taken to hiring a company called Mosquito Shield. They spray all over her yard, including the plantings along the adjoining fence line, so that the spray comes into our yard a little bit (and of course the vegetable garden is right in the line of fire).

This is very upsetting to us as we do not want to have problems with a good neighbor or pesticide on our food. I also suspect that something is happening to the insects and maybe even birds due to the spray. Our neighbor on the other side found a dying hummingbird in his lawn the day after the Mosquito Shield crew had sprayed; the fireflies were far fewer in number this year; the cicadas have not made a sound; and the crickets are almost silent.

I see this company's signs (and those of similar outfits) going up in other yards and am terrified that we will see a lot of wildlife, including our beloved bees, dying out in our area. Do you know anything about the chemicals Mosquito Shield uses? Is there a way to get information on the safety or lack thereof regarding this type of spraying? We are very upset about this and would appreciate any thoughts or suggestions you can offer!

---- Barbara in Wallingford, PA

A. I've been researching this company online ever since I received Barb's email a few weeks back; and information about the ingredients in their sprays has not been forthcoming. (Other online reporters say they have also been frustratingly stonewalled—to the point of conspiracy theories.)

Initially all I could find out about the company is that it's a national franchise that has locations in most of the East Coast states and West to Nebraska. Many of the websites dealing with the company are solicitations to buy a franchise; some are offers of spray packages to homeowners with lots of assurances and testimonials but no list of ingredients.

This level of secrecy does not seem to be the norm. A similar franchise called "Mosquito Joe" is very upfront about their options. They offer a choice of what they call a 'barrier spray' of pyrethroids (a common chemical insecticide) or an 'all-natural' alternative spray. The only difference in mosquito control is that the natural spray remains effective for two weeks as opposed to three.

'Joe' does not reveal exactly what's in his all-natural spray online, and I apologize that I just didn't have time to try and contact them before press time. (I was doing this research in-between monster sessions of tomato saucing [HUGE harvest this year; and you have to use it or lose it] and fitting in some vacation time), but it's safe to assume that it's a mix of the botanical oils that have been shown to be effective mosquito repellants. That's what the Mosquito Shield people say makes up 99% of their product.

What? I do know what's in what they're spraying?

Yeah—I called one of the local franchises and told them I was preparing for an outdoor wedding and wanted to know what was in their spray. It was a little tough getting the info, but they claim its {quote} "99% vegetable oil" plus {again, quote} "a very small amount of chemical pesticide, specifically one ounce in every gallon".

There are 128 ounces in a gallon, so the chemical pesticide makes up a little less than one percent of the spray—which can still be an enormous amount. Many pesticides are lethal to insects at half that concentration. The "vegetable oils" they identified include garlic, cedar oil, lemon grass and peppermint—all of which make sense, as these botanical sprays have a history as effective mosquito repellants.

Back in the early 90s, organic California growers were using a spray of garlic oil to try and control pest insects. Their workers soon noticed that they weren't getting all bit up in the field anymore, tests were run, and the spray they were using, "Garlic Barrier", began being sold as a mosquito preventative.

Cedar oil soon followed both alone and in mixes, as did the lemon-scented herbs and peppermint. I actually used the original "Mosquito Barrier" garlic spray to solve a huge mosquito problem at a series of operas being performed outdoors in Philadelphia's Fairmount Park years ago. (People were complaining that they couldn't hear the singers over the sounds of mosquito slapping and swatting.) The garlic oil spray worked so well that people called the opera company, afraid that we were spraying toxic chemicals!

Now—a diversion.

Research has shown that botanicals like garlic and cedar oil are effective 'barrier sprays' that repel mosquitoes for several weeks after spraying. But there's no research on their effect on other insects. These sprays would not injure bees, butterflies and beneficials, but they might repel them the same way they chase the skeeters—and 'no bees, no food'. So I would reserve use of these sprays to 'one-timers'—like a few days before an outdoor wedding. The rest of the year, you should be practicing mosquito prevention techniques that ONLY affect mosquitoes, like non-DEET repellants and BTI traps, because you want lots of good bugs in your garden.

And now, back to our story:

Our listener should send a formal letter or email to the service asking them to cease their overspray. It is illegal for a spray like this to land on someone else's property. I would also formerly ask to be notified in advance of each treatment and then hang a tarp on the fence that day or the day before to keep the spray off those veggies.

Long term, Barb should at least be able to convince her neighbor to hire a different service that only uses botanicals. Or offer to set up BTI traps on both properties; a much more sensible way to prevent mosquito problems.

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