Some observations in garden centers and nurseries, of which there are so many in the Moscow region, led me to write this article. Walking through the stalls, I automatically noted numerous damage to black currants by one of the most dangerous pests - the kidney currant mite.
For the first time this pest was discovered at the end of the 19th century in Scotland, in the 20th century for 50-60 years it populated currant plantations in Europe and already at the end of the 70s it was revealed in the suburbs. Currently, this species is found everywhere throughout Russia. Approximately 50% of blackcurrant seedlings can be found from single to numerous rounded buds, hiding several thousand adult females ready for oviposition. For this reason, it is imperative and very careful to examine blackcurrant seedlings for modified buds - if there are even slight swelling of the buds on the shoots, then it is better to refuse to buy such a plant. Visual diagnostics is possible only in spring or at the end of summer, when the buds are still or are already inhabited by currant kidney mites.
The biology of the currant kidney mite has been studied rather poorly, due to the difficulty of observing microscopic organisms. We most often determine the presence of a pest by swollen, rounded buds in the fall or spring after leaf fall, when visual diagnostics are most accessible. However, with a low population density, the presence of a pest can only be determined using a microscope when viewing a large number of slightly modified buds. This can explain that there is a latent period of infection of plantings in the first two years, when the shape of the buds does not change and, only in the 3-4th year, we can find spherical mite buds.
In addition, the kidney mite damages all types of currants without causing kidney changes. Such plants are the reserves of this pest. There is information that this type of mite can also inhabit gooseberries. In the spring, at the first warming and the beginning of kidney development, active feeding and egg-laying in the kidneys begin. It gives several generations, and their number depends on weather and climatic conditions. During the period of bud extension from the buds, the mass migration of ticks begins. Negative geotaxis forces the mites that emerged from the buds to move upward to the apical buds and developing shoots. Despite the external sluggishness, the ticks move quickly enough. In 1-2 days, pests can overcome the distance to the top of the bush.
Mass migration of kidney mites begins in the second half of May and continues until the first decade of June. The timing of the release of pests from the buds was determined using entomological glue applied to the shoots. The migratory mites adhered to the glue and were then examined with a microscope. On late varieties of currants, the timing of migration can be shifted and lengthened by 1–2 weeks. Already by the beginning of June, with the development of axillary buds, their first colonization with a tick occurs. Until autumn, a kidney mite gives 3-4 generations, and only with a decrease in temperatures and a reduction in the length of the day does it enter diapause until spring.
The development and nutrition of mites in a currant bud leads to tissue proliferation, deformation and disruption of the formation of inflorescences. Ultimately, she dies.
Tick control is carried out when 5-10% of infected kidneys are found. Kidney mites are carriers of a very dangerous disease - the doubleness of currants, leading to sterilization - a violation of the development of flowers and berries. Among the natural enemies of this pest are lacewing larvae and aphids, which destroy migratory pests, but this proportion is insignificant.The main route of infection with the kidney currant mite (often in the latent phase of development) is the planting material, possibly also pollinating insects.
Fighting currant kidney mites
- breaking off deformed buds and the obligatory treatment of the bushes with anti-mite drugs after that (a certain amount of mite remains in the place where the kidney separates);
- elimination of migratory ticks from mid-May to the second decade of June, and in the case of a cold, prolonged summer - until the end of June;
- disinfection of cuttings before planting with water - 45 ° C for 15 minutes;
- green currant cuttings.
The following insecticides can be used to kill ticks: Actellik, Fufanon, Bi-58 nov (phosphorganic - can partially destroy the tick in the kidney), Fitoverm, Vertimek (derivatives of actinomycetes - biological products), Demitan, Omite (acaricides, have only a contact effect during migration ticks, hazard class - 2!)
Photo by the author