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Turn a Triple Play Against Nasty Mosquitoes

This Summer: Prevention to Trapping to Repelling---Theyyyy're OUT!

Q. Dear Mr. McGrath: My lovely English Basement apartment includes a charming sun ken brick patio with a 6" diameter storm drain in the center. Every summer, the mosquitoes take up residence in the drain and eat alive anyone who dares step outside the house. I want to reclaim my patio! Most of the information I have found recommends larvicides. Would they work? I greatly appreciate any and all insight you may have.
               ---Alicia; Washington, DC

A. Hey, Alicia-I'm the one who MOST appreciates 'any and all insights' that turn up in my poor head. (When one does, I figure it probably got lost.) But I can answer your question-and use it to help others avoid getting bitten this season with a three-point plan for denying those bloodsuckers brunch onus.

1. PREVENT!
The best thing I ever learned about mosquitoes is that they don't travel far from where they breed, so if you take care of wet areas on your property, you'll GREATLY cut the mosquito population around your house for the rest of the season. First, do a 'water collection' inspection: Empty wheel barrows, boats, buckets, and other water-collecting objects; clean out clogged gutters(an often-neglected breeding site); and change the water in bird baths twice a week. Then get some "BTI".

The 'BT' stands for Bacillis thuringensis-a group of natural soil-dwelling organisms. The 'I' stands for is raelensis, the specific 'strain' of But that kills baby mosquitoes (and blackflies!) before they can leave the water as biting adults. Available as granules or floating 'dunks' and briquettes, BTI harms NOTHING else. Birds and fish can even eat 'Bt ed' mosquito and blackfly larva without any harm. Apply it to ponds, fountains and other standing water, and you'll have MANY fewer adults trying to suck you later.

Alicia: This is likely the larvacide you mentioned. BTI treatments generally last a month (that's how long the dunks and briquettes work in ponds), but that drain water probably changes after every rain, so I'd shake a few granules down there once a week. And, because the water down there isn't 'standing' all the time, I might instead try cutting a regular window screen to fit over the top of the drain and then tape or glue it in place.

Anyway, some of the brand names BTI is sold under include Skeetal, Vectobac, Mosquito Attack, Gnatrol, and Bactimos. I found my big yellow plastic shaker jug of "Dexol Mosquito Free Granules" at a local hardware store, and I've seen the granules and dunks at lots of garden centers.
They're widely available via mail-order too; "Mosquito Zapper" is one of many companies that sells both granules and dunks.

2. TRAP!
Last season, I had the chance to test a number of mosquito-trapping devices. I was not impressed with the "Sonic Web" (the one Hammacher-Schlemmer sells as the Sonic Insect Trap in their catalogs). It didn't catch many mosquitoes, but it did catch a lot of beneficial, and it seemed to work better when it was turned off! And it traps the pests on a giant visible lampshade kind of thing that is very gross to look at.

The machine that really seemed to do the job was The Mosquito Magnet. You've seen these things all around-they mimic human scent with a chemical attract ant called octenol and by using a gas-grill sized propane tank to create carbon-di-oxide; then the machines trap the attracted skeeters by sucking the minto anet. The 'Defender' (the cheapest model at around $300; protects half an acre) and 'Liberty'(around $500; ¾ acre.) both require electricity. The Pro size(over $1000; but it protects a full acre) is self-powered; no cord. The machines are widely available, both retail and mail-order.

Oh and PS: Nasty backyard bug zapper DON'T kill mosquitoes. Even worse, they DO kill lots of bugs that eat mosquitoes! Unplug it-its part of the problem, not the solution!

3. REPEL!
LARGE SCALE: Research has shown that mosquitoes avoid areas where high-concentration garlic sprays have been used. Garlic! I knew it: They ARE vampires! Anyway, one such product I see in a lot of retail stores is Victor's"Mosquito Barrier"; but there are lots of other brands out there as well, most in ready-to-use hose-end sprayer bottles; just check and make sure that" garlic oil" is the active ingredient. Spray it on your yard the day before a big party or other outdoor event and the garlic smell will go away after a few hours, but the mosquitoes will stay out for 2 weeks!

PERSONAL: Last season, I spoke with the author of a fabulous 2002 New England Journal of Medicine study on repellents. Very well-run study: Volunteers stuck their arms inside cages of hungry female mosquitoes to see what worked and what didn't.

What didn't work: Avon Skin so Soft kept the pests away for less than ten minutes. Wristbands didn't worked at all-whether their active ingredient was herbal or the chemical repellent DEET. But two chemical-free products DID work really well:

"Bite Blocker". Made by "HOMS", a North Carolina company, this combination of soybean, geranium and coconut oils provided complete protection for an hour and half, beating one of the DEET products tested. But Canadian researchers got even better results in two 1996 field trials-three and a half hours of 'complete' protection (much better than the DEET product they tested) in both studies. Available at some retail outlets, and Gardens Alive sells it mail-order, calling it "StingFree".
"Repel Lemon Eucalyptus Insect Repellant". This plant-based product provided complete protection for an average of two hours. Widely available, especially at camping stores; just make sure you get the right stuff-Repel also makes lots of chemical insect repellents.

I also suggest: Lemon-scented plants; many provide excellent protection when you crush up their leaves and rub them on your skin. ("The amazing plant" is actually a lemon-scented geranium.). In studies at the University of Guelphin Canada, lemon thyme was the best 'crush and rub' repellent (62% the repellency of the nasty high-concentration DEET product, "Deep Woods Off"!). I personally use lemon balm instead; it also works great, and it's MUCH easier to grow HUGE amounts.(Warning: This member of the mint family grows aggressively and must be controlled.)

On the horizon: Catnip! Perhaps the best plant-based repellent discovered so far, the University of Iowa has patented the active ingredient as a mosquito stopper, and we should see products that use it soon. In the meantime, try rubbing some leaves on your skin. Just don't complain if the cat tries to bat you around the floor.

Chemicals: I wouldn't use DEET if you paid me-large amounts of this chemical repellent are absorbed directly through the skin and then pass through your kidneys and liver on the way out. If you feel you MUST complement one of the' herbals that work', spray your clothes (not your skin-it won't hurt you, it just evaporates right away) with one of the .5% permethrin sprays generally sold for tick-bite prevention. (Repel and Sawyer both sell such sprays. But again, be careful-they also both sell a lot of harsher and combination(with DEET) products; so read labels carefully. You want a spray that contains ONLY a half a percent of permethrin.) That combination should keep you virtually bite-free.

Unless I show up, of course….

You Bet Your Garden ©2004 Mike McGrath


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