Recognize and prevent cabbage fly

Recognize and prevent cabbage fly

the essentials in brief

  • Cabbage fly larvae eat their way into plant tissue, where they are well protected from pesticides. Infested plants should be disposed of. Beneficial insects prevent the hatched larvae from boring into the root neck.
  • Larvae leave feeding holes in various cabbage plants in which there are feces and crumbs. Over time, infected plants wilt until they eventually die.
  • An infestation can be prevented by thorough tillage, mixed cultures and culture protection nets. Two types can occur in the garden: the large cabbage fly is less harmful than the small cabbage fly.

Can I control cabbage flies with home remedies?

cabbage fly

If the vegetables eat cabbage flies, it is worth digging up the affected plants and examining the extent of the damage. If the infestation is in the early stages, you can collect the maggots from the roots and replant the plant. If the stem tissue is already partially dead, only the complete disposal of the plant will help.

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To prevent further spread:

  • no composting
  • Compost offers cabbage fly larvae optimal living conditions
  • Disposal of infected plant parts in household waste

Natural regulation by beneficial insects

The natural enemies of the little cabbage fly include predatory insects such as ground beetles and spiders. The raven beetles of the genus Aleochara parasitize the pupae of the flower flies, while the parasitic wasp Trybliographa rapae prey on larvae. It is therefore advisable to plant species-rich fringing biotopes to promote such beneficial insects.

Create a border biotope

Sow the seed mixtures on a finely crumbly seedbed in autumn. The seeds are lightly incorporated so that they are not covered by more than 1.5 centimeters from the substrate. Light and dark germinators find favorable germination conditions at this sowing depth. To increase the germination rate, you can press the seeds down with a board. Avoid fertilization in order to suppress unwanted and competitive weeds. In the first two years, you should remove spontaneous weeds such as thistle, dock and couch grass.

Beneficial animals feel at home here:

  • Mixture as 50 to 60 percent comb, stalk grass and upright brine
  • a maximum of two percent legumes such as clover and vetch
  • Corn poppy, field delphinium, corn wheel and cornflower as a conspicuously blooming annual
  • biennial pioneer species such as evening primrose, wild carrot, adder's head and white carnation
Cabbage flies: illustration of a border biotope

Do pesticides help?

Cabbage flies belong to the mining insects. Your larvae eat their way into the plant tissue, where they are well protected from pesticides. Even in commercial horticulture, the control of the plant pest is difficult, because the larvae are not caught by the poisons.

This is how you can recognize damage to the cabbage fly

In spring, the infestation often extends over the edge rows. This first generation does the most damage. Seedlings that grow between March and May until the first pair of leaves have formed are at risk. As the season progresses, the pests penetrate the interior of the plant population.

  • Feeding tunnels in the root neck, stem and cotyledons
  • Food crumbs and droppings in the corridors
  • Plants wither and rot
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Affected plants

The maggots of cabbage flies cause damage to cabbage plants that grow close to the ground. Cauliflower is particularly vulnerable. The insects are considered dangerous pests on oilseed rape. In the private garden, they are based on the seasonal availability of various food plants. While fast-growing vegetables such as radishes are attacked by the first generation from April, the second generation prefers to eat Chinese cabbage, but also radishes and kohlrabi, in midsummer. Late-ripening species such as Brussels sprouts and swede are on the menu of the third generation in autumn.

Combating the mining cabbage fly larvae is extremely difficult.

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This is how cabbage flies multiply

Females orient themselves with the help of their senses. They use optical stimuli or fragrances to find a suitable place to lay eggs. Pressed juice from swede or the mustard oil glycoside sinigrin are very attractive. The female takes the potential food plant into consideration by crawling first on the leaves and then down the stem to the ground. The eggs are laid at the root neck.

  • oval eggs are about a millimeter long
  • about 100 eggs are produced per female
  • the first maggots hatch after four to eight days
  • dig into the root neck and penetrate to the root
  • Feeding activity extends over three to four weeks

This is how you prevent an infestation

cabbage fly

Since there are no pesticides for private use and the effectiveness of home remedies quickly reaches their limits, you should counteract the spread of pests through optimal gardening. Thorough cultivation of the soil is mandatory before every sowing. After the harvest, no stalks or leaves may remain on the bed, as cabbage flies prefer to overwinter here.

  • Early and late sowing bypasses the main flight time for flower flies
  • Put wood ash in the planting hole and sprinkle on the ground
  • Scatter rock flour (€ 14.95 at Amazon *) around the root neck
  • Spread a layer of mulch from fern leaves
  • vegetable fertilizers increase the attractiveness of the soil for females

Ecological balance through mixed culture

An important measure to prevent pest infestation are mixed seeds, in which opponents naturally arise. Tomatoes and celery are good partners for cabbage family, as they keep cabbage flies at a distance with their intense scent.

suitable partnersunsuitable neighbors
RapeseedClover, vetch, grain peamustard
radishCarrot, parsleyCucumber, Chinese cabbage
cauliflowerPhacelia, French beansGarlic, onions
Chinese cabbageSpinach, beans, lettuceRadish, radish
KohlrabiBorage, dill, leek, black salsifyCabbage
radishNasturtium, spinach, lettuceChinese cabbage, cucumber

Protect crops with a net

Since cabbage flies infiltrate a plant population, a protective net is considered to be the safest method to ward off the pests. It should be particularly close-meshed so that the flies up to five millimeters in size cannot access the food plants. The culture protection nets ideally have a mesh size of 1.8 millimeters. They are stretched across the bed immediately after the susceptible species have been sown and remain there until harvest.

Tips

There are special collars of cabbage that are placed around the stem of the young plants. They prevent cabbage flies from laying their eggs on the root neck. The collars made of felt or cardboard are removed shortly before the harvest and composted.

What types of cabbage flies are there?

cabbage fly

Cabbage flies belong to the genus Delia within the flower fly family. Well-known pests are small and large cabbage fly. While the small cabbage fly is active from April, the large cabbage fly (Delia floralis) only flies between August and September. It produces one generation per year and is therefore less harmful than the related species. Delia floralis mainly uses radishes and radishes as host plants.

Appearance

The little cabbage fly is reminiscent of a miniature version of the housefly. It grows up to five millimeters long and feeds on nectar and pollen. Their larvae develop near the roots. They are colored white, legless and headless. Their pupae appear brown and barrel-shaped. They can be found in the ground and are carried away by ants.

Tips

The predatory nematode Steinernema feltiae is an effective regulator of root fly larvae. So far, however, the beneficial insect has rarely been used against cabbage flies.

Way of life

The first generation of the little cabbage fly hatches in spring. The chestnut blossom, which takes place in the Palatinate at the end of April, serves as a guide. In such mild regions, three to four generations can hatch per season. Egg development is favored by warm temperatures under foil and fleece.

  • April : egg laying
  • May to June : larvae hatch, eat and pupate after two to three weeks
  • July : oviposition
  • July to August : development of the second generation of maggots
  • September : oviposition
  • September to October : Third generation larvae hatch and leave behind feeding damage until pupation

frequently asked Questions

Are there white cabbage flies?

Adult cabbage flies are not colored white. Their appearance is reminiscent of the appearance of a housefly. Your larvae do not live under the leaves but in hiding and are only visible when you pull infected plants out of the ground. If you see white flies on the plants, they are probably whiteflies.

Risk of confusion:

  • Moth whale : white flies on the underside of the leaf, fly up when touched
  • Cabbage white butterfly : first lays greenish and later yellow eggs on the underside of the leaves
  • Cabbage moth : green caterpillars eat leaves
  • Mealy cabbage aphid : powdered aphids suck on the undersides of the leaves

Why do cabbage flies infest cabbage plants?

These insects have specialized in cabbage family, because here they compete with a few food specialists. Many cruciferous vegetables contain mustard oil glycosides, which have antibacterial and antimicrobial effects. This protects plants from potential predators, but cabbage flies can digest the substances.

What damage can cabbage flies cause?

Because of its high reproduction rate and rapid development, the cabbage fly is one of the most dangerous pests on oilseed rape. It is able to completely destroy a crop. Since the flies are extremely mobile, they are rarely caught by insecticides. Their larvae develop protected in the root tissue. Since the largest plants are more strongly infested than less developed plants, early seeds show a greater infestation than late seeds.

Does plant manure from garlic or nettle help against cabbage flies?

Plant brews serve to strengthen weakened plants. Since cabbage fly larvae prefer to burrow into vigorously growing plants, manure made in-house does not provide reliable protection against infestation. Because of their intense smell, brews can be administered supportively.