Onion fly - Wanted poster and spray to fight

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Onion fly - Wanted poster and spray to fight: larvae

Quickly she is gone, the anticipation of young onions, tender leeks and hearty chives, when the onion fly strikes. The tiny insect specializes in the damage of bulbous plants. It is primarily the larvae that cause stinking feeding in crops. With up to three generations per season, the pests make life difficult for amateur gardeners. The following profile brings all the oppressive details to the point. Good to know that different sprays are ready to fight.


  • Insect family of flower flies (Anthomyiidae)
  • Genus: onion fly
  • Gray-black insects up to 7 mm long
  • Adult larvae up to 10 mm long
  • Up to 3 overlapping generations
  • Temperature optimum 20 degrees Celsius and higher
  • Wintering as a doll in the ground
  • Life expectancy up to 4 months

way of life

Effective control of onion flies is based on knowledge of their way of life. From April on, each course through the vegetable patch should be linked to an infestation check. At this time, the wintered dolls pop up to feed on dandelion or meadow chervil. If the females have sufficiently strengthened, they lay off their eggs, from which develops the first generation of greedy larvae. For oviposition they specifically seek the proximity of young bulbous plants, so that the hatched larvae feed on the tender roots and shoots. The result is an early death of the young plants. This nefarious activity continues in July, when the second generation goes to work, followed by a third plague in August / September. Since the plants have grown in the meantime, the infestation is less obvious and is better tolerated by the bulbous plants.
Tip: The beginning of the dandelion bloom optically signals the first slip of onion flies.


Since the tiny insects and larvae are not always visible to the naked eye, the damage picture is an important indicator of the presence of the onion fly. You should pay attention to this:
  • In the seed row wither onion and leek plants immediately after emergence
  • In the further course, the larvae continue to migrate to shallots, garlic or chives
  • The young plants are soft, rotten and can easily be pulled out of the ground
  • In the root area and near the ground whitish maggots can be seen
After about 3 weeks, the pupation takes place, but outside the host plant. Rake the beetroot, sometimes dipping the 6 mm small dolls out of the ground.


In view of the high pressure of attack, hobby gardeners often only have to resort to an insecticide approved for the allotment garden in order to save their vegetable cultivation. The following preparations have proven to be excellent for controlling onion flies:
Pest Free Calypso Perfect AF from Bayer GardenEffective against sucking and biting insects and their larvae on useful and ornamental plants. The proven product is ready to use and also detects hidden pests. As a contact poison, it has an immediate effect.
  • 500 ml from 7,90 Euro
Natria Bio Schädlingsfrei from Bayer
The spray agent acts on the basis of neem, a natural active ingredient of the Indian Neem tree. Within a short time, the preparation causes a feeding stop for a period of 3 weeks. Due to the partial systemic effect, onion flies and larvae are also recorded, which were not sprayed directly.
  • 30 ml pack from 9,90 Euro (3 ml is sufficient for 1 liter of water)
Etisso pest-free from frunol deliciaThe broad-acting sprayer attacks in particular sucking and biting pests, such as the onion fly. It is not harmful to bees and very productive. Even 100 ml of the concentrate gives 12.5 liters of spray mixture. The only drawback is the waiting period of 3-7 days until the effect occurs.
  • 100 ml pack from 6,90 Euro
Vegetable Pest Free Decis AF from BayerA classic against biting and sucking insects with the drug deltamethrin. Notwithstanding the rapid action against the voracious larvae, the bee danger of the spray brings with it a bland connotation.
  • 1000 ml spray bottle from 14,90 Euro
Tip: Experience has shown that onions are less frequently visited by onion flies than sown plants.

Biologically acting control agents

In an early stage of infestation or as a preventive measure, the following preparations come into focus in the natural garden:
Bio-spreading agent for vegetables from SchachtThe preparation is a bit out of the ordinary at this point as it does not have a direct effect on the onion fly, but specifically strengthens the endangered bulbous plants and other crops. Health-conscious hobby gardeners favor the organic litter compared to a pesticide, since the known disadvantages of spraying do not come into play here.Instead, the agent has a vitalizing effect on the plants, so that they quickly grow out of the threatened stage.
  • 600 g dispenser from 8,90 Euro
Organic Plant Spray Tansy & Vermouth by SchachtEnvironmentally conscious hobby gardeners plead for the use of tansy or vermouth tea in the fight against onion flies. If you do not want to mess with the preparation, grab the Schacht organic plant spray, which is ready for use. The remedy also has a revitalizing effect on the stressed plant after infestation.
  • 2.5 l canister from 19.90 euros

Make biological sprays yourself

Anyone who does not want to rely on purchased organic preparations, manufactures a spray for controlling onion flies itself.
RainfarnteeTansy is one of the daisy family and is rich in essential oils, tannins and bitter substances. On humans, the herb plant can be toxic, on the onion fly as well. How to make the tea:
  • the plant is collected in the summer, preferably in the early morning
  • Pour boiling water over the parts of the plant and leave to infuse for 24 hours
  • first express the tar residues and then strain (tar residues are not suitable as mulch)
A splash of liquid soap, Spüli or soy oil improves the adhesion of Rainfarntee on the affected bulbous plants.
wormwoodVermouth is at eye level with tansy when it comes to pesticide use. Regularly sprayed, the tea not only sells the onion fly, but numerous other uninvited guests who fuss over the vegetables. The production follows the same recipe as Rainfarntee.

stinging nettle

nettle infusion
In the natural garden omnipresent in ecological plant care, nettles also fulfill their task as pest control sprays to their complete satisfaction. The goal in the preparation is to let the infusion not fermented as long as he turns into Jauche. At this concentration, the effect on taste would be detrimental. How to proceed:
  • Fill 500 g nettle leaves into a bucket
  • pour over 5 liters of water
  • Cover with a grid to allow air to enter the mixture
In the following 2-3 days, the gradually fermenting liquid is stirred several times a day. Once the first air bubbles rise, the infusion is ready. As it flows through a coarse screen, the spray mixture is ready for use. Bring the stinging nettle 2 times a week in the vegetable patch until no more damage occurs.
ConclusionHer tiny, 7mm long body fakes over what damage the onion fly can cause in the vegetable garden. As soon as the first young onion, leek or chive plants emerge, the greedy larvae rob them of their vitality. When the second and third generations hit, the crops have already developed enough to cope with an infestation. Until then, under high infestation pressure, efficient spraying agents are sometimes essential for fighting. If the pest was discovered at an early stage thanks to its knowledge of the infected species, it would, with a little luck, be able to kill it and its brood biological control agents.

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