Treating a restaurant for flies can be a bit tricky because many have odd hours, and staff and customers usually are present. This can lead to having to maneuver around many obstacles.
Early on, I realized there was a common denominator in many restaurant accounts with swarms of fruit flies (Drosophilidae): leaky ice machines. Putting on my “pest detective hat,” I learned that if you shift the ice machine over the drain properly and the drain was cleaned, the water went down the drain and the flies disappeared. It was simply a matter of removing the organic matter and water from the equation. This trick isn’t 100 percent viable at every account, but heck — we all need to celebrate our small, but not insignificant victories!