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Fruit fly invasions can be explosive

Hanbidge on Horticulture
Patricia Hanbidge
Patricia Hanbidge

Last weekend we had a beautiful garden party as part of the Friday Evening in the Garden series. There was music, fabulous food, fellowship and a good quantity of fruit of the season. However, the morning light also revealed a host of tiny little fruit flies happily flitting about the fruit bowl. Fruit flies are evident in the home at any time of year, but they are most commonly encountered a bit later in the season.

The adults are easy to spot being a hefty 2.5 millimetres long with large red eyes and a tan to black body. Fruit flies lay eggs on fermenting fruits and vegetables and any other accommodating moist organic surface as long as there is some fermentation of some kind of organic material in process. The eggs will hatch within days and larvae will become breeding adults within a week. This is significant as each female may lay as many as 500 eggs in her short lifetime. This leads to a population explosion if all factors are favourable.

I have fond (or not so fond) memories of genetics labs that favour the study of fruit flies – specifically due to their prolific regeneration. However, for homeowners, this enormous breeding potential simply means that a little bit of fruit rot can quickly generate a house full of flies.

The infestations will generally originate when infested fruits or vegetables are brought into the home and left at room temperature, but adult flies may also gain entry through poorly screened doors and windows. At this time of year we have such an abundance of produce that many sites in the home are attractive to these little critters. Fruit flies will also breed in drains, recycle bins, garbage containers or even dirty mops or other cleaning apparatus that remain moist for a period of time.

The most important step in eradicating fruit flies is to locate where they are breeding. Any fruit or vegetables that are ripe should be refrigerated, eaten or discarded. If you suspect a drain is the prime breeding site, then tape a plastic bag over the drain for a night and look in the morning for adult fruit flies. If you find some then simply flush the drain with hot water to help keep it as clean as possible. It is also a good idea to use a fine mesh screen to prevent them from getting in and out of the drain area.

A simple trap can be set up on your kitchen counter by using a used and washed yogurt container covered with Saran Wrap. Simply place a banana peel in the container (or other fruit part), cover with saran wrap secured with an elastic band. Poke a number of small holes in the saran wrap big enough to accommodate the passage of a fruit fly. If you have a fruit fly problem, within a short period of time you will find the container will be filled with flies able to enter but unable to find their way out.  To take care of the captive flies, simply place the container in the freezer for a short period of time.

The life span of a fruit fly is relatively short, so once the breeding site is eliminated, adults soon disappear and once winter arrives, there is less chance of a repeat infestation.

— Hanbidge is a horticulturist with the Saskatoon School of Horticulture and can be reached at 306-931-GROW(4769); by email at growyourfuture@gmail.com or check out our website at saskhort.com