A closer look at the vinegar fly, including control and monitoring methods.
Drosophila melanogaster has a number of common names. ‘Fruit fly’ is probably most commonly used by the general public. However, a large number of different fruit flies exist, some of which are major pests in agriculture (such as the Mediterranean fruit fly), making the generic term ‘fruit fly’ somewhat confusing.
In the pest management industry, ‘vinegar fly’ or ‘fermentation fly’ are more commonly used and are probably the most appropriate names as they tie in with their feeding behaviours. The occasionally used ‘bar fly’ is probably too specific, as although they do cause problems in bars, they occur far more widely.
Species snapshot
Latin name: Drosophila melanogaster.
Common name(s): Fruit fly, common fruit fly, lesser fruit fly, vinegar fly, fermentation fly and bar fly.
Description: The standard ‘wild’ form is a mid-brown fly, about 2.5-3 mm long, with black stripes across the abdomen and large, red eyes. Varied in colour. It is a slow flying fly.
Distribution: It is thought to have originated in Africa but now it is found worldwide, thriving in temperate and tropical regions.
Diet: Fermenting fruit and decaying organic matter. Also of note, they are attracted to beer, wine and soft drinks.
Where they are found: Indoors they are found in kitchens and food storage areas. Outdoors they are found in orchards, vineyards and compost bins.
Pest status: They are a pest in domestic homes, restaurants and food management businesses. They do not bite and are not known to transfer disease. They are just annoying! In commercial situations their presence can impact reputation and may flag potential hygiene issues.
Vinegar flies as pests
Vinegar flies are really just a nuisance pest. They don’t bite or sting and they are not known to carry or transfer diseases. As the source of infestation can be difficult to locate, they can certainly be persistent. In the residential situation this is just annoying. But in the commercial situation, their presence can reflect poorly on the business. Certainly, patrons may feel their presence is an indicator of poor hygiene practices, which is probably true. For health inspectors their presence will present an issue, so it is important to eliminate a vinegar problem before it becomes a major infestation.
Vinegar fly infestations occur in kitchens, food storage areas and service areas (such as bars), anywhere where spilled or rotting food/drinks are left in place, unnoticed. Life cycle and key behaviours Drosophila melanogaster has a rapid life cycle – it can progress from egg to adult in seven days at 28ºC. With females able to lay 50-75 eggs a day, they can create a pest problem that can quickly get out of control.
Life cycle and key behaviours
Drosophila melanogaster has a rapid life cycle – it can progress from egg to adult in seven days at 28ºC. With females able to lay 50-75 eggs a day, they can create a pest problem that can quickly get out of control.
Both the adult and larvae feed on the same materials – rotting fruit, vegetables, decaying organic matter and spilled drinks (soft drinks, beer and wine). They are able to breed in very small amounts of food.
Vinegar flies tend to aggregate in groups, even in the absence of a food source. This can help in locating the source of an infestation, by not having to deal with a diffuse population.
Adult flies are attracted to light (UVA), especially when disturbed, although egg-laying females and the larvae are negatively phototactic. Preferred egg-laying and feeding sites tend to be in dark, undisturbed locations.
How to get rid of vinegar flies
The key step in eliminating a vinegar fly infestation is to carry out a thorough inspection to find the source of the infestation. Don’t assume there is a single source; in an established infestation is it likely the females have already found more the one location with a suitable food source. Remove the infested food sources and place them in a sealed plastic bag before disposing. Thoroughly clean the site of the infested food. For areas of drink spillage it can be a painstaking process to get into all the cracks and crevices. Even one small site left with a suitable food source can restart the infestation.
Once the site of infestation has been cleared, a residual insecticide treatment is rarely required. Any adults can be dealt with, with a suitable space spray, although due to their small size it is unlikely that all the adults will be killed. To prevent any remaining adults starting a new infestation, the use of vinegar fly traps can be considered.
Vinegar fly trap
Commercial vinegar fly traps are available, although it is relatively easy to build your own. Place apple cider vinegar and few drops of detergent in a small bowl. Place cling wrap or other suitable cover on the bowl, ensuring there are few small holes in the cover. Any adults will be attracted to the bowl, squeeze through the holes and get trapped. Such traps can also be used as monitoring devices.
Preventing vinegar fly problems
Ensuring good hygiene practices will prevent any problems with vinegar flies by making sure there are no attractive breeding/feeding sites. Drosophila are quite good flyers and can enter buildings from surrounding properties and gardens, so insect screens will have some benefit. Incoming fruit and vegetables should also be checked.
