Gesundheit für Mensch, Tier & Pflanze

Suillia lurida

Suillia lurida

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The garlic fly is one of the most important pests in garlic cultivation in eastern Austria. In the first days of spring, the pest lays its eggs at the base of the garlic stem. Damage ranges from slight curvature of the inner leaves to complete destruction of the plants.

Appearance

The garlic fly belongs to the family of mock flies (Heleomyzidae), is about 9.5 mm long and has a wingspan of about 18 mm. The body is reddish-brown in color, and the wings are mostly transparent with a grayish cast along the wing veins. Like all flies, it bears wing cilia instead of hind wings.

The eggs are white, about 1.2 mm long, and spindle-shaped. They have a highly sculptured surface.

The maggots grow up to 10 mm in size and have a pointed front end where the mouthparts show through as "nail hooks". The strongly hardened respiratory openings (stigmas) open at the posterior end.

The barrel pupae are oval, reddish brown and about 7 mm long.

Biology

In early spring as soon as the first shoots of garlic appear, flies seek out garlic fields. Eggs are laid in the soil near the base of each stem. Peak egg laying occurs in the first half of April, but earlier egg laying may occur due to warm periods in winter.

The newly hatched larvae bore into the shoot and feed on the young leaves. They go through three larval stages. Around mid-May, they leave the garlic plants and pupate in the surrounding soil. Flies hatch again from the pupa as early as the beginning of June. However, these no longer cause any damage, they overwinter and do not reproduce until the next spring.

Damage symptoms

Initial infestations are usually not noticed because the maggots feed on the innermost, young leaves. Their feeding becomes visible only when the affected leaves are pushed outward by growth. Beginning in April and continuing through May, the fly larvae can be found in the winter garlic shoot. From late April/early May, externally visible damage can also be seen.

In spring, the innermost, newly appearing leaves show feeding marks of the fly maggots in varying degrees: these range from jaggedly frayed lateral margins with curvature and twisting of the leaf to complete retardation of growth in the main shoot.

Often in such cases, numerous weaker side shoots are formed. The plant then acquires a "grass-like" appearance and the garlic cloves remain small.

Host plants

This pest only attacks winter garlic, but not summer garlic grown in spring. There are also differences between individual varieties with regard to susceptibility: the landrace of garlic used in the Weinviertel region is less severely infested or can survive an infestation better. In addition to garlic(Allium sativum L.), the garlic fly was also observed on onion(Allium cepa L.) and leek(Allium porrum L.).

Economic importance

The garlic fly can cause severe damage to garlic. In the 1980s, its occurrence was reported for the first time in Lower Austria (Kahrer, 1986). Due to the increased area cultivation of garlic, up to 70 % infested plants were recorded according to Kahrer (1986).

Prevention and control

  • A preventive measure is to cover the garlic with a protective culture net or fleece. However, this must be done at the first warm days of spring. The crop should then remain covered until about the middle/end of April.
  • The choice of cultivar is also important, as stem-forming garlic cultivars are less severely attacked. In addition, damage there does not have as strong an effect.
  • As a chemical measure, spraying with preparations suitable for the control of seed or root flies can be considered (see list of plant protection products approved in Austria). Experience shows that the best time for treatment is around the beginning of April, when 10% of the examined plants are covered with eggs. At lower temperatures, the preparations are ineffective. In any case, a wetting agent should be added to the spray broth.

Specialized information

Publications

Kahrer, A., 1986. studies on the biology and control of the garlic fly (Suillia lurida [Meigen]; Helomyzidae; Diptera) in Austria. Pflanzenschutzberichte 47(1), 40-47.

Last updated: 24.11.2021

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