fruit flies attacking ripening fruit

Asked June 23, 2020, 12:46 PM EDT

Help! my pie cherries are a loss, I just discovered my beautiful strawberries are bags of juice too and now ripening blueberries show signs of piercing/softening. I can't spray without harming pollinators for the staggered blossoming of my berries. I have one trap but heard they don't like rotting fruit like normal fruit flies so normal lure won't work. is there any treatment for them that will not harm me by eating it or harm my pollinators? Can I use fresh juice of some kind? add anything? what is best placement? thanks! Maureen

Lane County Oregon

1 Response

Dear Maureen,

Hi and thanks for contacting Ask an Expert
You are talking about the Drosophila fly, a fruit fly that likes all fruit unfortunately whether ripe or green. They pretty much go for all types of fruits.
The Drosophila fly along with the regular fruit flies are plaguing our fruit and have been for several years. A common way to get rid of a lot of them is to put out bottles with holes large enough for them to get in filled with molasses and water and ammonia. I use large and small bottles, sometimes gallon jugs and pierce the plastic with not quite a 1/2 inch. I put about 1/4 cup of molasses and ammonia in it and add water to mix. You can skip the ammonia and add vinegar and some vegetable oil with the molasses. I have many of the traps in the plum trees. They work. The pollinators are done with the trees since the fruit has set so they are not around. I have never found a bee in these traps.
You can stop the fruit flies from getting your strawberries by putting row cover over them BEFORE they infiltrate. The row cover is not expensive and will keep out all kinds of bugs if there are no gaps around the plants.

Make sure you pick up all fruit on the ground, pick and dispose of the over ripe strawberries, etc. Keep the garden clean from rotting fruits of any kind.
I am attaching a link from Oregon State on this pest.
https://extension.oregonstate.edu/pests-weeds-diseases/insects/spotted-wing-drosophila-swd There are multiple articles on this pest. While these articles are geared toward farmers, as a gardener you can use some of their information for your fruit.
You can also spray your fruit with a clay substance that will keep them out for a while, it must be sprayed again as the fruits enlarge. This clay is easily washed off. And you can net your trees. To do this you need a nylon netting with tiny holes like a bride's veil made of tulle and again it must be completely closed off - no openings.

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