The spotted drosophila is increasingly giving hobby gardeners a queasy feeling because it is spreading more and more. In fruit growing, it can sometimes cause considerable damage. But there are ways to prevent an infestation or stop it from spreading.

Only very fine-meshed nets keep vinegar flies away

Table of Contents

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  1. the essentials in brief
  2. Damage caused by cherry vinegar fly
  3. Recognizing cherry vinegar flies
  4. combat
  5. host plants
  6. frequently asked Questions

    7. the essentials in brief

    • Cherry spotted drosophila lay their eggs on soft-skinned berries that are in the ripe state. The smell of rotten fruit is attractive.
    • Damage is caused by sap leakage and larval development. Consequential damage can be caused by fungi and pests. There is no health risk for humans.
    • Spotted flies can be recognized by their red eyes. Males have dark spots on the tips of their wings. Females have a conspicuous laying apparatus.
    • An infestation can be prevented by protective nets or clay. Preventive measures such as fruit selection, early harvest and regular mowing are important.

    What damage do cherry vinegar flies do?

    Females of the spotted-wing drosophila lay their eggs through the sawn-open shell into the flesh of previously undamaged fruit. This distinguishes the species from the domestic vinegar fly, which prefers to fly to overripe fruit. It is not possible to tell with the naked eye whether eggs have been laid on a fruit. Research has shown that the drosophila does not transfer vinegar bacteria to the fruit. However, consequential damage is possible due to the opened fruit skin:

    • Secondary pests find entry points
    • Feeding activity of the larvae causes sap leakage, which attracts pests
    • Sap residues provide breeding ground for rot fungi
    • quantitative and qualitative harvest losses

    digression

    egg laying

    A female spotted wing drosophila can lay between seven and 16 eggs per day. In the course of their entire lives, the number adds up to around 400 pieces. She does not proceed arbitrarily in the search for a suitable egg-laying place. Research has shown that a natural coating of fungi, yeast or bacteria on the fruit surface favors the decision.

    If a female has laid her eggs on a fruit, she marks this area. This prevents other females from laying their eggs in the immediate vicinity. Mild temperatures and sufficiently high humidity ensure that a maggot hatches from the egg.

    damage potential

    The black-bellied fruit fly (pictured here) does more damage than the spotted-wing drosophila

    The spotted drosophila (Drosophila suzukii), which originally comes from Asia, was first observed in Germany in 2011. In the three years that followed, the pest spread across the country. The species is favored by the increasingly mild climate. When temperatures drop below zero in winter and rise sharply in summer, populations automatically decrease. Observations of the infestation in recent years have shown that the damage potential of the spotted drosophila in viticulture is lower than the damage caused by the black-bellied fruit fly (Drosophila melanogaster).

    Dross drosophila can cause damage in viticulture and orchards. Particularly endangered areas are in the vicinity of forests and high meadows.

    Dangerous to humans?

    If you are unsure whether the affected fruit is still edible, you should trust your senses. Look closely at the fruit and smell it. If you don't smell any unpleasant odors, taste the pulp. Even freshly infected fruit containing eggs or newly hatched larvae are harmless and not harmful to health. In the late infestation stage, injuries with juice leakage are clearly visible and the fruit gives off a vinegary smell. Such fruits are inedible.

    Dealing with the harvest if infestation is suspected:

    1. only harvest apparently intact fruit
    2. Harvest as soon as the fruit ripens
    3. Stop egg development by chilling the harvest
    4. Heat the pulp or soak in alcohol

    Even fruits infested with larvae can usually still be eaten

    Recognizing cherry vinegar flies

    At first glance, the Japanese spotted wing fly looks like native species. It has a yellow to brown colored body and dark stripes on the abdomen. Cherry vinegar flies appear lighter in color than fruit flies. The red eyes are striking. The larvae are white in color and cylindrical in shape. They reach a size of 3.5 millimeters. While females differ from other species in their laying apparatus, males have one striking feature:

    male female
    size 2.6 to 2.8 millimeters up to 3.4 millimeters
    wing each wing tip with dark spot transparent
    abdomen nondescript sharply toothed egg-laying apparatus

    Control cherry vinegar flies

    The Asian spotted wing fly can be controlled with insecticides. But in the private sector, chemical agents are not a solution. With suitable alternatives, you can ward off the fruit pest biologically without endangering your health.

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    Build a trap yourself

    Traps are easy to make yourself from recycled plastic cups with lids. A disposable cup for smoothies or other drinks with a capacity of 500 milliliters is ideal. While not enough to completely eradicate the infestation, they can be used to control it.
    Craft instructions:

    1. Poke 3-4 mm holes in the lid
    2. Mix apple cider vinegar and water (1:1) and pour into the cup to a height of four centimetres
    3. Add drops of detergent
    4. Hang the trap in the shade at fruit level
    5. Use cable ties to attach

    It is necessary to place them as early as possible before the fruit ripens in order to detect the infestation in good time. Drosophila species get into the trap through the small openings, while unwanted by-catches of larger insects are prevented. Prepare a double set of traps so that you can easily swap out the containers and then renew them.

    kaolin

    Kaolin is better known as china or white clay. The main component is kaolinite, which from a chemical point of view is an aluminum salt of silicic acid. After at least four sprays, the finely ground powder, dissolved in water, prevents cherry flies from laying eggs. The effect lasts until the next rain. If the flies are dusted with the agent, the fine particles adhere to the body and trigger an excessive urge to clean. The flies forget to eat and neglect reproduction.

    Benefits:

    • Bless you: no danger for humans and pets
    • biodiversity: no killing but only deterrent effect
    • effectiveness: Uniform particles form an evenly dense spray coating

    nets

    Fine-meshed nets keep the spotted-wing fly away from the fruit

    Protective nets are ideal for private use if you want to protect isolated bushes from infestation by the spotted-wing drosophila. It is important that the net has a maximum mesh size of 1.2 millimeters and is hung completely over the bush. Even the smallest gap allows access. The disadvantage of this variant is that opening the nets allows flies to get to the bush. Therefore, only open the covers on hot and dry days when there are no cherry vinegar flies in the air.

    tips

    In order to increase protection against the arrival of cherry vinegar flies, you should cultivate the covered bushes in a greenhouse if possible.

    preventive measures

    If possible, you should defoliate affected fruit bushes moderately. In this way, the trees are better aerated and more sunlight falls inside. Dross drosophila is less attractive to shrubs that are dry and exposed to strong sunlight. The surrounding vegetation should also be kept as low as possible if an infestation is suspected in order to promote warm and dry conditions.

    What you can do:

    • Thin out fruit before maturity and remove damaged fruit
    • Do not leave fallen fruit as the smell attracts drosophila
    • Mulch soil to speed up rotting processes

    tips

    To identify an infestation, you can store fruit in a close-meshed mesh bag and observe it over the next few days. In warm temperatures, the flies hatch within a short time.

    Which plants do drosophila attack?

    Drosphila suzukii is not picky about host plants. Females prefer to lay their eggs on soft-skinned fruits. Red grape varieties with a compact structure and thin skin and cherries are particularly attractive. Late-ripening fruit varieties are also at risk because of the strong propagation in the summer months. The spotted-wing drosophila also attacks wild berry bushes such as raspberries and blackberries. Apples and pears are only attacked if the fruit skin is already damaged.

    frequently asked Questions

    Does fruit lime help against the cherry vinegar fly?

    Fruit lime is ineffective against the spotted-wing drosophila

    Fruchtkalk is a milk of lime that is used as a white coat for fruit trees. It contains slaked lime and helps against fungal diseases. No effect could be found in the control of spotted wing drosophila. Glued color charts and products with lavender oil are equally ineffective.

    What is the infestation of raspberries and blackberries?

    As part of a research project by the Bavarian State Ministry of Food, Agriculture and Forestry (StMELF), it was determined at which ripening stage cherry drosophila prefers to lay their eggs on raspberries and blackberries.

    While no eggs were found in unripe blackberries with a slight red colouration, almost all random samples of raspberries that were beginning to turn red were affected. The redder the blackberries became, the more eggs were in the pulp. The number of eggs in ripening raspberries, on the other hand, decreased slightly. In both cases, the females preferred to look for fruits that were fully ripe.

    Can I see a spotted drosophila infestation early?

    It is difficult to recognize an infestation in time. It is not possible to tell with the naked eye whether there are eggs in the pulp. Only the presence of pupae can be determined with a magnifying glass. The pupae have two appendages protruding from the fruit bowl. Typical for the pupae of the spotted-wing drosophila are star-shaped extensions, which do not appear in pupae of related species.

    How do cherry vinegar flies live?

    The species prefers mild temperatures and moderate conditions. If the thermometer rises above 30 degrees, the activity of the insects is restricted. At more than 32 degrees, no more reproduction takes place. Adult flies survive the winter in a frost-free hiding place. They wake up in the spring when temperatures rise to ten degrees. Because of these claims, the species was able to spread across large parts of Europe.

Category:

Animals in the garden