Gall mites are annoying but usually relatively harmless creatures in gardens. The tiny animals cannot be seen with the naked eye - rather, an infestation is expressed by the typical galls, small squirrels on the leaves of the host plants. Read what you can do against the pests below.

The galls differ in shape and color depending on the mite and tree species

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  1. Portrait gall mites
  2. fight gall mites
  3. harm to people
  4. frequently asked Questions

    5. What exactly are gall mites?

    Gall mites, zoologically Eriophyidae, are tiny mites that appear to us humans primarily as gate pests. They belong to the subclass of mites within the class of arachnids and form a family with 274 genera and over 300 different species (as of 2013).

    Look

    The whitish, brownish or yellowish colored mites have a body length of only 0.08 to 0.5 millimeters, which is only possible due to a missing cardiovascular system. Larger species can be recognized with a magnifying glass, the others only under the microscope. Gall mites are worm-like and slightly curved in shape and are armored on top with dorsal plates. Unlike other mites, they only have 4 legs instead of 8.

    way of life

    Gall mites hibernate in fruit mummies, under bud scales or in the leaf axils of their host plant and move from there to the sprouting leaves in spring. They suck on the leaves with their jawed claws and cause characteristic protuberances, also called galls or smallpox, in which they reside and multiply, through the release of enzymes in the saliva.

    The development of the larvae through the nymphal stage to adult gall mites can take place within about 10-15 days, so that there can be an enormous population growth within one season. The dispersal of the animals takes place via the wind. Gall mites reproduce particularly well in dry, warm conditions.

    damage picture

    The linden gall mite has specialized in linden trees

    Gall mites parasitize different plants and cause different types of damage to them. Most affected are trees and shrubs such as maple, hazel, alder, plum, elm, beech, lime, dogwood, walnut or coniferous trees, as well as berry bushes such as blackberries, currants and raspberries and grapevines. Many of the gall mite species specialize in certain plants and are also named after them, such as the linden gall mite (Eriophyes tiliae), the apple rust mite (Aculus Schlechtedali) or the walnut smallpox gall mite (Aceria tristriata).

    maple conifers linden tree hazel blackberries currants
    damage picture squirrel-shaped protuberances (galls) that later turn reddish on the leaf surfaces Hollowing and brown discoloration, then falling off of the needles Felt-like spots on the leaves Swollen, enlarged 'round buds' that do not sprout and die Inhibited fruit formation, berries remain completely or partially red and inedible: loss of harvest Swollen round buds, stunted, asymmetrical leaves, growth retardation, possible transmission of nettle leaf defoliation, resulting in inhibited fruit formation
    combat Remove affected shoots and leaves In the case of severe infestation, spray treatment with oil preparation or, in extreme cases, cut back Remove affected plant parts Break out swollen round buds, remove affected parts of the plant Spray treatment with oil preparation or liquid manure, cut back infested plant parts, dispose of fruit mummies Break out swollen round buds, cut back the affected parts of the plant, dispose of the mummies, spray with oil preparation or liquid manure, keep the soil moist

    The so-called galls are typical of damage caused by gall mites. These are protruding tissue growths on the upper or lower sides of the leaves of the host plant. The mites are also named after these galls. The galls are typically squirrel to tuberous in shape and may be light green and later brownish or reddish in color.

    Gall mites leave crescent-shaped galls on maple leaves

    However, other symptoms can also occur: Hazel, yew, currant and gooseberry show swollen, enlarged buds that serve as a refuge and laying site for entire hordes of mites. Such infected round buds no longer sprout and die off. Lime trees show felt-like spots when infested, and the leaves of hornbeams curl up. On birches and willows, bushy or spherical adhesions form, so-called witches' brooms or, on willows, muddled heads.

    In the case of blackberries, fruit formation is also inhibited. The berries do not fully ripen, remain partly or completely red and are therefore inedible. Anyone who grows blackberries on a larger scale can suffer a significant harvest loss from gall mites.

    Certain species of gall mites also transmit diseases. For example, currants can become infected with the stinging nettle leaf virus due to a gall mite infestation, which in turn leads to reduced fruit formation.

    Apart from the crop losses in blackberries and secondarily also in currants, the damage caused by gall mites is limited to the visual disfigurement and leaf loss of the plants. The infestation is not really dangerous, i.e. seriously damaging to them.

    fight gall mites

    As different as the symptoms of a gall mite infestation look on the different host plants, the possible methods of combating them are just as diverse. As is so often the case with pest control, gall mites should be counteracted both preventively and acutely.

    prevention

    The prevention of gall mite infestation begins with the selection of plants and their planting site. If possible, you should not settle plants that are susceptible to the pests in particularly warm, dry and sheltered locations, because such an environment promotes the reproduction of gall mites. You should also avoid excessive nitrogen fertilization, but the plants should still be sufficiently supplied with it.

    In the case of blackberries, late-ripening varieties are particularly affected. So, if it doesn't matter to you, choose a variety that ripens early.

    tips

    Especially with the susceptible berry bushes, there are now certain varieties that are resistant to gall mites. For example the blackberry Rubus fruticosus 'Choctaw', the red currant Ribes rubrum 'Rovada' or the raspberry Rubus idaeus 'Willamette'. You can also specifically ask about other resistant varieties in gardening shops.

    Acute countermeasures

    If a gall mite infestation has already occurred, phased measures to contain the population should be implemented throughout the season. The most important measures are as follows:

    • remove infected plant material
    • Spray cures with oil preparations, brews and liquid manure
    • Use scavengers
    • Keep soil moist and loose

    Remove infested plant material

    Affected plant parts should be removed promptly

    As soon as you notice a gall mite infestation, you should first remove as many infested parts of the plant as possible. Especially by breaking out the swollen round buds of hazel, currant, gooseberry and yew, you can eradicate a good part of the mites in the spring. It is best to dispose of the infected buds that have broken out in the household waste, but certainly not in the garden. Heavily affected shoots and branches should be cut off completely and also destroyed. A radical pruning is also suitable for plants that tolerate pruning well.

    From the later fruiting phase, the fruit mummies, which are used by the gall mites as winter quarters, must be removed.

    Spray cures with oil preparations, brews and liquid manure

    In the case of plants on whose leaves the gall mites produce the typical galls, the best way to combat the pests is during the migration phase. The migration phase is the phase in which the mites leave their hibernation sites in the fruit mummies or under the bud scales and migrate to the sprouting leaves. During the vegetation phase, you can then apply a treatment with oil preparations (usually based on rapeseed oil) or home-made plant brews or liquid manure, also on a weekly basis during the growing season. In the case of blackberries, the young shoots are treated when they have reached a length of about 10 centimetres, then again after a week and a half and finally just before flowering.

    The following have proven to be effective, natural remedies against mites:

    • tansy brew
    • garlic extract
    • nettle manure

    1. Tansy decoction

    For a tansy decoction, chop up about 150 g of fresh tansy herb, scald it with about 5 liters of boiling water and let everything steep for 10 minutes. Then filter the brew. Filled into an empty flower sprayer, you can then treat the affected plants with it.

    2. Garlic Extract

    You can make a garlic extract by steeping approx. 100 g of crushed garlic cloves in 20 ml of oil for 24 hours. Dilute the filtrate with one liter of water and add 10 ml of curd soap.

    3. Nettle manure

    Nettle manure helps against a wide range of pests

    Nettle manure is generally a proven, ecological plant strengthener and fertilizer and can also help against gall mites. To make nettle manure, chop up about a kilogram of fresh nettles and pour 10 liters of rainwater over them. Cover and leave to ferment for about two weeks, stirring daily. When no more carbon dioxide is formed, i.e. no more bubbles rise, the liquid manure is ready and can be filtered off. To use as a spray against gall mites, dilute the carefully filtered broth in a ratio of 1:10 with water and apply it to the plants using a flower sprayer.

    Use natural predators

    It can also be very helpful to use natural predators against the gall mites. They mainly include predatory mites (Gamasina), which are sold in carrier granules. The granules can usually be spread directly onto the affected parts of the plant. The predatory mites eat both the larvae and the adult gall mites and die as soon as they can no longer find any gall mites.

    In addition, lacewing larvae can also be used against gall mites. They are sold in cardboard combs in the first or second instar larvae. It is imperative that they are deployed according to the enclosed description so that the lacewing larvae do not cannibalize each other.

    Keep soil moist and loose

    Especially with infested fruit trees and berry bushes, it is also helpful to keep the soil loose and moist if there is a gall mite infestation. Rake up the soil under the plant from time to time and water evenly. Mulching with bark or straw helps to retain moisture.

    Effect of gall mites on humans

    Like many other mite species, gall mites can also be harmful to humans. First and foremost, allergic reactions are possible. Bites from gall mites usually manifest themselves in the form of small pustules with itching and redness. In severe cases, however, they can also trigger more serious diseases such as Lyme disease, typhus, tularemia or rickettsial pox.

    It is therefore important for sensitive people in particular to wear protective clothing, especially gloves, when combating the plants. You should also be careful not to take clothing worn during the measures into the house to avoid spreading it to houseplants there.

    frequently asked Questions

    What are gall mites?

    Gall mites are known to us humans primarily as a plant pest. As mites, they belong to the arachnids and form a family with 274 genera and over 300 species. They are microscopic and cannot be seen with the naked eye. Only the damage they cause to maple, hazel, plum trees, blackberries or currants is visible. Squirrel-shaped bulges on the leaves are characteristic.

    How can you identify gall mites?

    Gall mites themselves cannot be seen, but their works can

    The animals themselves are not recognizable with the naked eye and usually not even with a household magnifying glass, because they are only about 0.08 to 0.5 millimeters in size. Under the microscope, their worm-like, whitish, brownish or yellowish body can be seen with only 4 legs instead of the 8 legs common to arachnids and mites. An infestation of plants with gall mites can only be recognized by the damage that is evident on the plants.

    Which plants are attacked by gall mites?

    Deciduous trees such as maple, lime, hazel, alder, beech or elm are particularly affected, but coniferous trees can also fall victim to the gall mites. Shrubs such as dogwoods, blackberries, raspberries and currants are also affected.

    What is the damage caused by a gall mite infestation?

    Typically, a gall mite infestation is shown by greenish to reddish or brownish, squirrel-shaped bulges, the galls, on the leaves of the corresponding plants. However, felt-like spots, swollen, non-sprouting and dying round buds, asymmetrical or curled leaves, stunted growth and inhibited fruit formation (in the case of blackberries, the fruit is completely or partially red) can also occur.

    How to fight gall mites?

    Combating gall mites varies from plant to plant. If only the leaves are disfigured by the squirrel-shaped galls, these should be removed and discarded. Spray treatments with oil-based preparations or with homemade tansy brew, garlic extract or nettle manure can also be used. Fruit mummies in which the mites hibernate should be carefully removed and destroyed. In the case of cut-tolerant and severely affected plants, a radical pruning can also be announced.

    Are gall mites also dangerous for humans?

    If necessary, gall mites can cause allergic reactions in humans. They manifest themselves in the form of pustules, itching and redness. In unfavorable cases, the mites can also trigger diseases such as Lyme disease, typhus, tularemia or rickettsial pox.

Category:

Animals in the garden