QUESTION:

What is the best plan of action for a large retail store that has a small food service in the front of store with a bad fruit fly problem? In another setting fruit flies are getting bad in a coffee location where some food is served along with a seating area for people to eat and drink coffee. What sources could you suggest that would tend to be sanitation issues.

ANSWER:

Fruit flies, also called vinegar or pomace flies, tend to occur close to where breeding sources are available, although it's not beyond the realm of possibility that they may be coming in from outdoors. This seems especially to be the case in late summer and early fall when we have those "Indian Summer" days of warmth and moisture. A lot of home gardens and fruit trees are losing their crop to fall to the ground, creating an abundance of opportunities for the flies. But, we should assume that your situations must have some attraction and possibly breeding source available. Anything sugary and fermenting is the draw for vinegar flies, so in food service areas this commonly will be the soda dispensing machines. There may be spills under and around the equipment itself, but it is important to be able to open the machine and take a good inspection inside. Leaking tubes can dribble soda syrup onto the interior, and this can breed a lot of flies.

The adult flies may be attracted to the dispensing nozzles themselves, so cleanliness is important here. Inspect the floor all around the areas where the employees make and serve the food, as spills tend to accumulate and get kicked under the counters where they may not be removed with regular cleaning. The cleaning, even if it is done daily or some other regular interval, may tend not to be very thorough, so debris gets pushed into crevices along walls and under equipment and left there. A crack against the wall with even a slight amount of food debris can breed large numbers of these tiny flies. Look for discarded food containers that are lying unnoticed under counters. If there is a salad bar it needs to be inspected carefully, including underneath where spills may accumulate. Check items like mops to see if they are cleaned and allowed to dry properly, as a wet mop with food debris in it serves as a major attraction and breeding source. Check all drains to be sure they are not filled with organic sludge buildup, as drain flies or the phorid flies that resemble fruit flies breed easily in these areas.

In a facility that serves coffee there could also be some of these other fly resources, such as spilled sugary foods, but so many coffee service facilities serve the wide variety of sugary drinks now too that spills of these materials could attract or sustain fruit flies. It takes a good flashlight and knee pads and patience to make that very detailed inspection in all of the hidden places to find the source of the problem, but this is necessary if eliminating the flies is to be done. One perfect example was a heavy vinegar fly problem that was finally traced to several beer bottles with lime wedges in them that had been kicked under a counter in a bar. Inspect the waste stream in these accounts to ensure that garbage containers are properly maintained - washed daily, plastic bags in place and emptied daily. Inspect the refrigerators to see if there is any buildup of water under them, along with the normal accumulation of debris that seems to end up under large, heavy appliances.

It would be helpful to use some of the fruit fly traps in these accounts. These use only attractants such as vinegar to draw the flies into the trap to drown, but they can help you to pinpoint just where the source may be. UV light traps will capture a lot of the adult flies, but of course do nothing to resolve the source of the problem. Applications of labeled residual insecticides also can kill a lot of resting adult flies, but again do not get to the heart of the problem, which is wherever there is some spill or discarded food that the larvae are breeding in.

View past Ask Mr. Pest Control questions.