I am a very active sitter, which leads to a lot of poop! I am very diligent in cleaning up after the dogs but this summer there have been a TON of flies in my back yard. You can't eat out on the deck without them landing on your food. Are the flies from the dog poop even though I clean up often? I can't think of what else they would be coming from.
Yes they are.
Get some eco bug killer. They are safe around people and pets. They use only mint oil or lemongrass oil...it works!!! We use some from Home Depot and OSH. One is called Poison Free and one is called EcoSmart and one is Hotshot Natural. There are others, too, that use herbal oils. The smell isn't bad, either, just a strong herbal smell. They have flying insect and crawling insect sprays, indoors or outdoors. Spray the deck area before you go outside and voila...no flies.
And hose down the deck and lawn first...wherever the dogs go.