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University
of Rhode Island GreenShare Factsheets
Vinegar
& Fruit Flies Drosophila
spp.
Diptera: Drosophilidae
Vinegar
and fruit flies often become nuisances in homes, restaurants, fruit
markets, etc., especially when associated with decaying or rotting
fruit and vegetables. Indoors, flies may be seen hovering around
overripe fruit and vegetables, baked goods containing yeast, garbage
cans and beverages such as fruit juices, cider, soft drinks, beer,
wine and vinegar. A rotten fruit or vegetable, a dirty garbage receptacle,
an unclean dishcloth or drain water in refrigerators can yield a
heavy population of these flies very quickly. Outdoors, they become
numerous during summer and autumn where fruit and vegetables are
harvested, suddenly disappearing with the arrival of cold weather.
Some species can serve as carriers of disease as they are attracted
to human and animal excrement as well as fruits and uncooked foods.
Adult
vinegar flies are about 3 to 5 mm (1/8 to 1/5 inch) long, dull
brownish-yellow to brownish-black with red eyes in some species.
The head and thorax
are tan-colored, while the abdomen is black and gray underneath.
The wings have two "breaks" in the leading edge near the body.
The third antennal segment is oval or long with the outer bristle
(arista)
nearly always feathered. Eggs are pearly white with two to four
threadlike tubes seen under magnification. Larvae are about
2 to
5 mm (1/10 to 1/5 inch) long, cream-colored, legless, eyeless and
tapered to a point at the head end. Larvae have an extended
stalk-like
breathing tube at the tail end of the body. Pupae are about 3 mm
(1/8 inch) long, brown and seedlike, with two hornlike stalks
at
one end. Female
flies lay about 500 eggs (up to 2,000 eggs) singly near the surface
of moist, fermenting food material such as overripe fruit, rotten
vegetables, dirty garbage containers, slime in drains and waste
materials. Eggs hatch in 24 to 30 hours into tiny larvae that feed
near the surface of fermenting food masses. Larvae feed principally
on the yeast in the fermenting fluids for five to six days and crawl
to drier portions of the food or even out of it to pupate. The larva
transforms into the pupa in the last larval skin (puparium). Newly-emerged
flies are attracted to light, become sexually active in about two
days, mate more than once and are strong fliers, traveling up to
6-1/2 miles in 24 hours. The life cycle may be completed in 8 to
15 days, depending on the temperature. Drosophila spp. have been
widely used by geneticists in studies of the laws of heredity since
it is very prolific, easy to rear and has a short life cycle. Sanitation:
It is most efficient to concentrate on eliminating the larval feeding
sites and breeding sites in order to manage large populations. Sometimes
simply eliminating an overripe banana, jars of fermenting home canned
foods, cider, fruit juices or dirty garbage cans will control these
pests. All exposed fruits and vegetables not consumed immediately
should be refrigerated before fermentation begins. Check garbage-laden
drain water, clean the gelatinous material in drain pipes, and install
(16 mesh) screens since these flies can pass through ordinary house
fly screening. Successful control includes eliminating all possible
breeding sites; sites can be found by placing masking tape or clear
plastic taped over garbage disposals and drain openings overnight
to detect fly emergence. Trapping:
One commercial, nontoxic, pesticide-free vinegar fly trap is
known as "Bio-Logic Natural Catch Plus Fruit Fly Trap." This convenient
ready-to-use vinegar or fruit fly trap reduces fly populations
70
to 80 percent or more by using a simple food-grade vinegar to attract
the flies. Traps are placed three to four feet apart on countertops
or in display cases of onions, bananas, tomatoes, salad bars or
wherever flies are a problem. These simple, safe, low-maintenance
traps remain effective, approximately 30 days. A
Mason jar with black paint or paper to cover the top third makes
a good trap. Coat the inside of the jar with a sticky liquid such
as diluted honey or vegetable oil. Invert the jar over a bait such
as crushed bananas. Rest the jar upside down on two blocks of wood
to allow flies space enough to feed on the bait. After leaving the
bait, they fly upwards to the light portion of the jar, rest on
the sides and are killed or become stuck. Adapted
from the Ohio State University Extension, 1999
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
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