We're having a problem with flies in our yard, and can not for the life of us figure out why. I think they may be bottle flies, but not positive - they are kind of iridescent looking.

1. We have no pets, there is no standing water, no food waste, or other organic matter that I can think of other than the mulch.

2. The other day it was so bad, that you couldn't even be on the patio. They were buzzing around everywhere, and seemed to be particularly interested in the small garden area which contains hydrangea, hybrid roses, knockout roses, a crape myrtle, a lilac and an ancient hydrangea tree. There is also a large potted tomato plant there and a few pots of flowers I haven't gotten into the ground yet.

3. This is right by my detached garage. The garbage is kept out there, however, there is only 2 people living in my home and we don't make much waste. Typically there isn't garbage laying out there since they come to pick it up twice a week and we barely fill 2 bags a week, rarely more. When we put things out into the garage, it's tightly tied up, and a lid is on the can - and it's out the a day at the most. We are careful about cleaning our recycling items as well.

4, Our neighbor, has a compost bin, which we are concerned is not being tended properly. We are worried this may be the cause of the fly infestation but it doesn't seem to be a reason why they would be hanging out in our yard - it would make more sense that they would be sort of "passing through" our area, than making a home here. Last year, we did notice a lot of flies near our front door, which is closest to where they keep the bin. We also had many getting into the house each time we would open the door plus, we had holes in our basement windows on that side of the house - so they were getting in there also. Thankfully, those windows were replaced so that shouldn't be an issue this year but they still hoover around the front porch as well.

5. They also have a cat that seems to think our porch and yard, is it's partial home. I do wonder if it's using ours as part of it's toilet facility although I have yet to see any evidence of such.

6. Under ground, in the back7 garden area, is an old well/cistern/*something* we discovered and uncovered a while back. While doing renovations on the garden, the lid cracked and we had to do a makeshift cover for it. The old one was concrete, all we could do was get a huge piece of heavy steel to put over it - then landscape fabric, and then back fill with all the dirt. I do sometimes wonder if possibly the water down there may be attracting them? Would this be something flies may find desirable to be near?

7. Could it be the weather? It's been incredibly rainy in New Jersey all spring, and now the past few days have been really hot and humid. It seems to have started recently. There's a lot of mushrooms springing up in the mulch everywhere, all kinds of odd fungus I've never seen before.

8. Could it be the type of mulch in general? It's just good black mulch. Or caused by over-watering maybe?

9. Last summer, we had a bad infestation of fruit or drain flies in the house. I keep things pretty clean so not sure if it was due to fruit going bad, or if they appeared because of other reasons - such as the neighbor's compost bin being so close to the house and poorly tended. I would hate to have to go through that again this year - it took weeks to get rid of them.

I think that's all the background I can think of which may be pertinent. If I missed something, please let me know. Any thoughts of what may be causing this?

Thanks.

Laurie