Rainy and cool weather, persisting inFor a long period of time, poses a great danger to orchids, as it contributes to the appearance of such a formidable disease as black rot. This disease occurs as a result of the planting of the plant with fungi (for example, Pythium ultimum or Phytophthora cactorum) and affects a wide variety of orchids, but Cattleya is particularly susceptible to them (lat.
Black rot, if left untreated, quicklySpreads throughout the plant and is as quickly transferred from one plant to another, hence, in a short time, it can destroy the entire collection of orchids.
Fungi, which cause black rot of orchids,Can live only in a humid environment. These fungi consist of so-called zoospores, capable of self-movement in water - they swim in it. If such contaminated water is on an orchid leaf, zoospores can enter the plant tissue and begin the next phase of their life cycle. At this stage, the fungus develops a vegetative part or a mycelium consisting of hyphae, thin threadlike tubes, which quickly spread throughout the tissues of the plant. And as soon as this happens, the first visible signs of infection - small, watery, transparent spots - expand and turn into large brown or black patches.
If the fungus infects seedlings - and this, as a rule,Occurs on the surface of the soil - the young plants are killed because of the black leg. For adult plants, the disease can strike on any part of it - on leaves, roots or pseudobulbs, but more often it originates on new growing leaves and progresses down the plant, reaching the roots. Affected leaves can turn yellow around the infected area, and the lesions will be soft and when pressed they will ooze. However, the most dangerous is the rot of the roots and bases of pseudobulbs, since it leads to the fastest death of orchids.
Non-sterilized pots, contaminated water forWatering, as well as water from affected plants, are all sources of the fungus. To avoid contamination of plants in the open air, they must be raised to a height of 90-120 cm above the ground. Do not leave the leaves of the orchids moist for an extended period. The key point in the prevention of the disease is a good air circulation in the place where the orchids grow, which will ensure the rapid drying of plants after watering or rain. Improve air circulation and thus prevent the rotting of orchids at home will help, for example, fans. At the first sign of infection, all affected plants must be isolated to avoid further contamination of the entire collection. Finally, to prevent the appearance of black rot on new shoots, some producers recommend using fertilizers with a high calcium content in the spring.
To stop the spread of black rot onOrchid, first of all, cut (cut out) the affected part of the plant so that at the same time remove a small amount of healthy tissue bordering the infected zone. Use only with a sterile instrument (knife, scalpel, etc.). Next, you need to carefully study the cut off part. Sometimes you can see a brown lesion inside the tissue that looks healthy outside. In the case of sympodial plants, such as cattleya, in order to stop the further spread of the disease, it is necessary to cut out all diseased pseudobulbs. If the plant is heavily infected, it is necessary to cut out part of the rhizome, piece by piece, until a healthy tissue appears. In a monopodial orchid, such as a vanda or phalaenopsis, one must remove the infected part of the leaf or, if necessary, the whole leaf. It is necessary to stop the spread of the fungus as soon as possible before it reaches the crown, and when the death of the orchid will be inevitable. Then you must put the plant in a well ventilated room and make sure that the cut is well dried and healed.
After the infected parts have been removedPlants, to protect the remaining healthy tissue, it is necessary to apply a fungicide. Cinnamon is an excellent fungicide. You can sprinkle ground cinnamon directly on the affected areas, where the infected parts of the plant were cut. It is also recommended to mix cinnamon with glue on a casein base or with vegetable oil> to get a thick paste. This paste is quite waterproof and can be used to cover the wound. Regardless of the chosen method, fungicide should protect all open (cut) places. It acts as a sealant, clogging up all wounds, so a new infection can not get into them. Another treatment option is the impregnation of affected plants with a fungicide. For example, to protect seedlings from the black leg, you can water them with water with a fungicide immediately after planting. Two weeks after this, it is necessary to repeat the treatment with a fungicide for preventive purposes.