Extension Service: Fruit flies, more breeds and more of them, are becoming too common

The fruit fly populations are prospering as a common kitchen-counter annoyance this winter. These flies are also commonly referred to as vinegar flies and scientifically as, Drosophila melanogaster. They seem to literally appear from nowhere and in great numbers, on any banana or tomato or orange or grapefruit and worse yet on the edges of that refreshing cerveza or red wine glass. Yuk!

And when shooed away they go directly for the eye or up a nostril. Part of this overabundance is due to the typical reasons, such as rotting citrus from trees growing outside the lanai or no-charge freebies from grocery purchases of fruit or vegetable products. Scientists haven’t tracked their long-distance range, but I bet it is at least a few hundred feet for these little Diptera.

Diptera is the group of insects in which these two-winged pests belong. These little flies, sometimes called vinegar flies, are attracted to lights. Hurricane Wilma’s winds opened a lot of fly-size entries through lanai screens and little cracks in doors and window frames. The storm also created a lot of leaf and fruit debris that if not raked away and cleaned up, may provide an excellent environment for maggot development as the vegetation decays.

The one-eighth inch long, red-eyed, tan fruit flies seek out damaged fruit on your counter tops and yeasty slime in your drains to deposit eggs. These guys reproduce at a rate that makes aphids jealous. Each female deposits 15 to 20 white eggs each day until they tucker out with a grand total of 500 to 900 eggs per female. The eggs hatch into little white maggots in three days and a batch of new adults appear in about 10 to 14 days after the eggs were deposited.

What to do? Sanitation is the key. Nasty as some of it is, rotting fruit shouldn’t be left on the ground. I think that there were close to 1,000 grapefruit on my tree this year and frequent cleanup has been a necessity. Cover fruit on the counter. Use plastic containers or some of those picnic “tent” devices as a covering.

Check for water or waste in corners under the sink, flush those kitchen sink drains and other household spare bathroom sink and tub drains with detergent, Drano or the homemade baking soda/vinegar preparation recommended by the county recycling department of Collier County (see www.colliercountyrecycles.com; go to the Information page and click on “Cleaning with a conscience”).

Carefully inspect fruit at the store before bringing it home. Recently, a fancy centerpiece made of elaborately carved melons and other fruit arrived at an event with an ensuing entourage of fruit flies, which put a dipterous damper on the decorations.

Thorough, daily cleanup in eateries is critical, especially those that have fresh veggies ready to go on your plate or sub. Various homemade traps can be tried, see Dan Culbert’s article at this Web site:

okeechobee.ifas.ufl.edu (go to news columns and articles, Nov. 10, 2004- vinegar flies)

Also, search the internet for a Victor Fly Magnet for another type of jar trap. Pull out that Dust Buster hand-held vacuum to remove the immediate swarms and then destroy the fruit. Using the Dust Buster while they are distracted on the fruit (they aren’t there just for the fruit) yields more captures. Use “Invite” Fruit Fly Lure (Rockwell Labs) on sticky fly-paper or tacky glue traps as another tactic.

One reason for more fruit flies is that we have more species than in previous years. A fruit fly native to tropical Africa was discovered in central Florida in July 2005. This flashy looking species is a primary pest of edible figs (attacks healthy figs through the natural opening which is peculiar to that fruit). It will also visit other damaged fruit as well. This fruit fly, Zaprionus indianus, looks just like our fruit fly, but has two sets of bold, white racing stripes on its head and thorax.

Fortunately, this red-eyed fly only produces about one-eighth as many eggs as our established vinegar fly. I found the first record of these flies in Collier County at our extension citrus grove in mid-January. I haven’t seen them inside the house yet, only on rotting grapefruit outdoors. So look closely and see if your fruit flies have white racing stripes. It may be a new neighborhood record! See:


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Doug Caldwell is the commercial landscape horticulture educator with the Collier County Cooperative Extension Service. For more information on home gardening, contact its Master Gardener Plant Clinic 9 a.m. to noon and 1 p.m. to 4 p.m. Monday, Wednesday and Friday at 353-2872. For more landscape information visit: collier.ifas.ufl.edu.

© 2006 marconews.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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