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Are you surprised that your blackberries do not fully mature despite sufficient sunlight and good care? The cause of this phenomenon is the Brombeergallmilbe (Acalitus essigi). The white animals from the family of the Gallmilben (Eriophyidae) are between 0.1 to 0.17 millimeters long - they can be seen therefore only with the help of a strongly magnifying glass.
The most striking feature of an infestation with Brombeergallmilben is - as already mentioned - the uneven ripening of the fruits. Like the raspberry, the blackberry belongs to the so-called collective stone fruits and is botanically not a berry. The fruit consists of several small individual fruits with soft flesh and hard seed, which grow around the fruit cone and appear to the hobby gardener as the actual fruit. This explains why often only a few segments remain red. In the case of very heavy infestation, only reddish fruits may be left on the shrub at harvest time. Due to the suckling action of the blackberry mite, the black berries often lack the sweetness that is typical of them.
way of life
Brombeergallmilben overwinter on stalk parts, under bud scales or on dried fruits of the plant, which are still partially hanging on the bush. In the spring, the mites finally migrate into the unfolding buds. There they lay their eggs on the undersides of the leaves. During flowering, the pests usually remain on the sepals of the plant. As soon as the first berries develop, the small animals sit hidden on the fruit bottoms and suck out the juice of the fruit. Per year the Brombeergallmilbe forms eight to ten generations.
Brombeergallmilben overwinter under bud sheds, populate the spring in the new shoot and in summer the flowers, before sucking on the fruits, which give them a striking black and red color
Blackberry mites prefer a dry heat and spread mainly in spring and summer. To prevent the pest, keep the soil around the shrubs moist, for example through a layer of mulch. Plant your shrubs sufficiently apart to ensure good air circulation. Do not use high nitrogen fertilizer.
In late winter, cut down heavily infested shrubs completely at ground level. In this way the winter hiding places of the microscopic Brombeergall mites are destroyed. With an ejection spray, you can combat harmful insects that overwinter on fruit trees in early spring, before they cause significant damage. A specially approved plant protection product based on rapeseed oil stops the development of the animals in good time. The gall mites are covered with a fine film of oil, which prevents the respiration of the arachnids and makes them suffocate. Since the product is non-toxic, fruits that grow on the bush after treatment can be consumed without hesitation.
Attention: As useful insects such as parasitic wasps and predatory mites overwinter on the woody plants, they can also be damaged by such treatment. For this reason, you should only spray your plants with plants that were heavily attacked by pests in the previous year. A Austriebsspritzung is not recommended as a purely preventive measure.