Dry Bulb Mite

Aceria tulipae

Services Related Content
Changed on: 22.10.2018
Icon Icon
Knoblauchmilbe in einer Rasterelektronenmikroskopischen Aufnahme.
caption
SEM image of a dry bulb mite

The dry bulb mite is a gall-mite family member (Eriophydae), a group in the subclass of mites. Despite their name, they do not produce any gall.

Adult mites have two pairs of legs on the thorax, while their abdomen is cylindrical and features rings on the outside. Two long, prominent bristles are located at the posterior end of their bodies. The mites are only 0.3 mm long and are barely visible to the naked eye.

More information
Knoblauchmilbe in einer Rasterelektronenmikroskopischen Aufnahme.
caption
SEM image of a dry bulb mite

The dry bulb mite is a gall-mite family member (Eriophydae), a group in the subclass of mites. Despite their name, they do not produce any gall.

Adult mites have two pairs of legs on the thorax, while their abdomen is cylindrical and features rings on the outside. Two long, prominent bristles are located at the posterior end of their bodies. The mites are only 0.3 mm long and are barely visible to the naked eye.

More information

Biology

caption
Stereo microscopic image of a dry bulb mite (ca. 0.3 mm long)
Stereomikroskopische Aufnahme einer Knoblauchgallmilbe (ca. 0,3 mm lang)

The mites go through two larvae phases during their development. Their very short pincer-like mandibles prick the tissue only on the surface. As a result, only severe infestation will leave visible damage on the leaves, which will twist slightly and stick to each other when unfurling. The mites are mainly found in the central veins, the midribs, of the leaves.

The mites are also often found in the plant’s inflorescence, from which they can easily migrate to the bulblis. As a result, the growth of heavily infested tree onions will be affected, causing the bulblis to vary greatly in size.

Once the plant’s leaves die, the mites will move to the bulblis and the cloves in the ground, where they sit well protected between the clove and the surrounding leaf. If the temperature is warm enough, they will start to reproduce and will be found in a small hole below the tip of the clove. Light infestation is basically undetectable, thus it may occur that lightly infested cloves might be stored after harvest. Should the cloves be stored at too warm temperatures (summer temperatures, not cooled), the mites will multiply rapidly and the cloves will dry out as a result of the pricks.

Minute pirate bugs (Orius species) and predatory mites from the Tydeidae family have been found on heavily infested inflorescences in the wild as natural predators.

Symptoms

The mites live in the green parts of garlic and liliaceae during the vegetation period.
They prefer young tissue, especially the small spaces and crevices of undeveloped leaves and inflorescences. Each female lays about 25 eggs, from which the larvae hatch after a short period of time.
Their piercing-sucking leads to the yellowing and twisting of the leaves. Younger leaves cannot develop because of being blocked by stunted old leaves.

caption
Symptoms of twisted and stunted leaves after dry bulb mite infestation
Symptom der Blattverdrehung und mangelnde Blattentfaltung bei Befall durch die Knoblauchgallmilbe

Heavily infested cloves in storage can be recognised by their light weight caused by them drying out. They can be squashed easily and are yellow to brown when peeled.

Hosts

The dry bulb mite affects garlic and liliaceae, such as tulips. Their supposed connection to the mosaic virus in wheat is based on an error. 

Distribution

Dry bulb mites are found in the warmer parts of Europe and North America and can be introduced by cultivating infested propagation material. They are believed to be able to overwinter outside – laboratory tests showed that these animals were able to survive temperatures as cold as -24°C.

caption
Drying garlic clove as a symptom
Eintrocknende Knoblauchzehen als Folge eines Befalls durch die Knoblauchgallmilbe: die Zehen schrumpfen langsam ein und werden gelblich - ihre Oberflächen sind von feinem Staub (Milben) bedeckt.
caption
Discoloured clove
Verfärbung der Knoblauchzehe
caption
Mass infestation of dry bulb mites
Massenhaftes Auftreten der Knoblauchgallmilbe

Control

Dry bulb mites behave like storage pests in a larder or storage room. The infestation starts with lightly infested garlic or tree onions and is easily missed.

  • The most important step in avoiding mite damage is to seed only healthy seeding material. Never use uninspected material designated for consumption, as it may be already affected.
  • When using tree onions for self-reproduction, the inflorescence should not be left until the bract opens, as the mites could easily migrate to the flowers and, thus, the tree onions.
  • Seeding material should be stored in a cool place so that existing mites cannot reproduce. The individual garlic batches should be stored at a distance from one another so that the mites cannot migrate to uninfected cloves.

Chemical methods to fight the mites on garlic in storage are still very unrefined: some books suggests dusting the bulbs with sulfur or having licensed companies gas the harvested bulbs in sealed rooms.

At present, AGES Wien is working on the development of future biological control measures, in addition to establishing a warning service for the dry bulb mite.

x