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Most of the higher plants have a green coloration of the terrestrial parts. Chlorophyll is a part of special cellular organelles - chloroplasts.
Chloroplasts are those organelles of the plant cell that are responsible for assimilating and transmitting the energy of sunlight, the more intensely the leaves are colored, the more chlorophyll they contain, the better the processes of energy conversion and production of organic compounds from inorganic compounds are. The process of decreasing chlorophyll in leaves is called leaf chlorosis. There are several causes of leaf chlorosis.
- Infectious causes of chlorosis
- Measures to combat chlorosis of an infectious nature
- Non-infectious leaf chlorosis, its elimination
Infectious causes of chlorosis
The reasons for the change in leaf color are viral and bacterial plant diseases. If the leaf blade begins to change its color to a paler or yellower, starting with leaf veins, then most likely the plant is infected with the yellow mosaic virus.
As a rule, plants are affected at the beginning of the growing season. Stripes and strokes of yellow appear on the leaf plate, which later merge into solid spots, the leaf gradually dries out and falls off.
Most often, the pathogen is in the soil, it is the soil fungus Polymyxa, its spores are transferred to the plant together with tools for tillage. This can be clearly seen on the plantings of cereal plants affected by the fungus.
Various insects, such as aphids, can also serve as carriers of the yellow mosaic virus. On plantings of leguminous crops, yellow mosaic virus, which causes chlorosis of leaves, is carried by some species of aphids.
If the infectious chlorosis began at the beginning of the growing season, then the crops of peas, soybeans, beans may die completely, in later periods not only leaves, but also flowers are damaged, which significantly delays ripening and reduces productivity.
In addition to viruses, infectious chlorosis can be caused by mycoplasma-like organisms, which are carried by various insects: beetles, cicadas, nematodes.
Fruit trees and berry crops are also susceptible to infectious leaf chlorosis.
Here, pathogens can be transferred along with pollen, during flowering of plants, or with grafting material, during vaccinations. The most susceptible to apple trees, stone fruit crops. As a result of necrotic changes caused by chlorosis, the affected leaves die off, reducing the ability of plants to photosynthesize.
In fruit trees affected by chlorosis, there is a delay in fruit ripening, and their number can be halved. In European countries, vineyards suffer greatly from chlorosis of an infectious nature.
Vegetable crops can also suffer from chlorosis. Microorganisms that cause various plant diseases, accompanied by leaf chlorosis, are distributed throughout the globe, so prevention and treatment measures are relevant for any agricultural area.
Measures to combat chlorosis of an infectious nature
Due to the fact that pathogens of infectious diseases accompanied by leaf chlorosis are transferred in several ways, control measures should primarily be aimed at:
- soil disinfection
- decontamination of tools
- extermination of insect vectors
- disinfection of seed
Various soil fungicides are used to disinfect the soil. Soil fungicides include chemical preparations used to treat soil in order to destroy microorganisms that cause plant diseases, as well as to destroy vectors of these diseases, such as nematodes and others.
Soil cultivation and treatment of plants in preventive maintenance is carried out in early spring, for this, solutions of copper, ferrous sulfate, nitrafen are used.
A number of soil fungicides are used in dry form, for example, the granules of the heterophos preparation are introduced into the soil to a depth of 10 cm around the plants, after which the plants are well spilled with water.
Many gardeners do not think about the fact that such gardening tools as a shovel or hoe need to be decontaminated. At the end of the season, the tool can be treated with technical alcohol or doused with boiling water - this will kill microbes, further storage in a cold room in winter will prevent them from reproducing again on the working tool.
When there is a threat of infection, seed and planting material is treated with fungicides.
Timely treatment of a garden or vegetable garden with pesticides reduces the number of insects - carriers of pathogens accompanied by chlorosis.
Non-infectious leaf chlorosis, its elimination
The appearance of yellow spots on the leaves can be caused by the composition of the soil.
The main reasons for the occurrence of non-infectious chlorosis can be a high content of lime in the soil, or a significant lack of basic minerals, or the lack of conditions for their assimilation, this primarily applies to the following substances:
An excess of zinc, copper and manganese can also lead to chlorosis. At the initial stage of non-infectious chlorosis, light-colored spots appear on the leaf blade without affecting the veins.
Drilling and leaf death begins from the edges, the tops of the shoots dry out, young leaves are damaged in thickets and more severely than old ones. To neutralize lime, colloidal sulfur is introduced into the soil or it is spilled with a weak solution of sulfuric acid.
With a lack of iron, the leaf blade turns yellow relatively evenly over the entire area, the veins remain green. To eliminate chlorosis in this case, you must use according to the instructions the preparations "Ferrovit" or "Fe +"
With a lack of magnesium, chlorosis manifests itself first along the edges of the leaf plate. The edges not only brighten, but also tuck down. The yellowness gradually spreads to the entire leaf, but the thickest veins and adjacent areas remain green.
The addition of magnesium sulfate will eliminate the problem.
With a zinc deficiency, the leaves become small, grow with yellow specks, gradually the leaf plate becomes a faded yellow. Sowing alfalfa will help enrich the soil with zinc.
A delay in the growth and development of plants occurs with a lack of sulfur. At the same time, the leaves first brighten, and then acquire a reddish color. Lack of sulfur very often externally manifests itself in the same way as lack of nitrogen. Laboratory analysis of the green parts of the plant and soil will help to accurately determine the content of chemicals.
The introduction of organic and phosphorus fertilizers, in the production of which sulfur is used, will eliminate the sulfur deficiency. It should be remembered that an excess of certain substances is just as dangerous for the leaves as a deficiency.
Therefore, when the first signs of leaf chlorosis appear, it is advisable to use the services of an agronomic laboratory and take soil samples from the site and possibly some parts of the plant for analysis. With the timely identification of the cause of chlorosis, taking measures to eliminate them, you can return the plant to a healthy look.
Detailed information on chlorosis in the video: