As an Aussie, my experience with flies is extensive. In some places I've lived in, talking outside during spring and summer is a risky business because as soon as you open your mouth, kamikaze flies make a beeline straight for it. On any given day during the warmer months, my coffee cup is likely to be the final resting place for a couple of the drowned critters. You get used to it - mostly.
But if you're not like me and have no intentions of getting used to them; instead of reaching for the traditional fly pray; there's some other strategies you can use to at least control and minimize their presence before needing going to that extreme.
The problem with fly spray and other commercial insecticides is it contains some nasty stuff; which isn't nasty just to flies; but to humans and other creatures in the environment - even the low allergenic varieties. Some of the chemicals include:
Bioresmethrin - a suspected endocrine disruptor and highly toxic to fish even in small amounts
Bioallethrin - a suspected endocrine disruptor and carcinogen
Synthetic Pyrethroids - Pyrethroids shouldn't be confused with Pyrethrum, which comes from the chrysanthemum,they are chemically designed to be more toxic and take longer to break down. Aside from being a suspected carcinogen, they are extremely toxic to aquatic organisms and are moderately toxic to birds. Pyrethroids are toxic to all insects, both beneficial insects and pests.
Here's some tips to help keep flies off your and control their prescence to a degree around your home - the greener way
Potted plants indoors
I received an email the other day from someone who was having problems with flies emerging from potted plants - something I hadn't heard of before. After a bit of research, I found the best way to deal with this is to reduce watering and organic matter in the soil of potted plants; particularly the top layer - gnats and flies thrive in damp conditions where's there's plenty of organic material.
Clear garbage
As flies breed in rotting organic material, make sure your garbage is secured. It can take as little as a week for adult flies to emerge from these sources. Check all mouse traps regularly and around your yard for other critters that may have died as even a small decaying animal can be a feasting ground for hundreds of flies. Unfortunately, common houseflies have a flight range of at least 5 miles (8Km), so unless you can organize a mass effort in your suburb; while clearing matter flies feed on and breed in; at best you may minimize them.
Secure compost bins and worm farms
Pretty much related to the above point - one person's garbage is another's compost. Try to keep dairy and meat scraps out of your compost bin or worm farm; that will discourage some types of flies. Even vegetable waste will be a nice breeding ground for some types flies (aside from fruit flies) as I discovered last year. I was able to reduce the the problem somewhat by putting mosquito netting over the worm farm; but I think I was a little late in doing so - best to apply the netting as soon as it starts getting warm.
Fly strip/paper
Not so popular now, but still very useful. These are non toxic strips embedded with something such as honey and also an adhesive. The flies land on it and are, well.. stuck.
Fly curtain
If you have people coming in and out of your house regularly, especially children, chances are they'll bring flies in with them. A simple fly curtain made of strings of beads will greatly reduce the number that do get in. During this summer in the outback, I rigged up one for my van and while every time I stepped outside I'd immediately get blanketed in them, a quick brush off, then through the curtain and none followed.
Citronella oil and candles
Citronella oil is an essential oil extracted from the different species of Cymbopogon. It's considered a biopesticide and non-toxic. Burning a citronella oil candle or incense sticks will not only repel flies, but mosquitos too. You can also buy special preparations of citronella oil to apply directly to your skin as a fly/mosquito repellent, but it does need to be applied more often than synthetic repellents.
Fly repellent plants for the garden
Some species of plant you may be able to grow in your yard depending on your local climate conditions to help discourage flies. These include Lemon balm, Catnip, Mint, Chrysanthumums, and Marigolds.
Check your flyscreens
OK, so this is a no-brainer I guess; but small holes in flyscreens are easy to miss - so it's a good idea to check them regularly during the season. The added benefit will be to prevent mosquitos from annoying you (or worse).
Fly traps
Fly traps come in various shapes and size, and some are very easy to make - such as this bottle trap - it's a great way to keep at least one plastic bottle out of landfill :).
Light
Flies will tend to be attracted to and congregate in dark areas, particularly when it's hot, so allow as much natural light into your home as you can.
"Green" fly sprays
If all else fails, there are some "green" fly sprays hitting the market that contain natural pyrethrum and citronella blends. We have used these from time to time and found them to be quite effective on flies; not so good on other insects.. which mightn't be a bad thing actually.
Do you have some environmentally friendly fly repelling tips you'd like to share? I'm sure that many folks will be grateful for the information, so please add your ideas below!