Orchids: reproduction and care
Let’s see how to multiply our hydrangeas and how to keep them free of pests and diseases
- Reproduction of simpodial growth orchids
- Reproduction of monopodial-growing orchids
- Pests of orchids
- Diseases of orchids
Reproduction of simpodial growth orchids As we saw in a previous article, simpodial growth orchids are those that develop pseudo-bulbs from a rhizomatous stem. Well, when the orchid has developed 6 to 8 pseudobulbs we are in a position to separate the plant by cutting the rhizome with scissors previously disinfected and applying healing paste in the cuts; we will place the new plants in their new pots with new substrate and in a place with little light. The operation can be carried out at the beginning of spring or beginning of autumn which is when the plants have the most reserves.
Once the plants are separated, we will proceed as in a transplant.
The reproduction of monopodial growing orchids are those orchids that have a single main stem that grows erect from the center of the plant. We will make sure that the rods are in perfect sanitary condition and we proceed to cut each rod into three pieces. With a sharp knifewe will throw the cover of the yolk and introduce the rods in a mixture of pine bark and sphagnum moss, moisten with a sprayer and cover with a transparent plastic; we place the rods in a place with little light. Every two weeks we uncover and moisten the substrate and if everything goes well before 10 weeks they must have taken root.
Pests of orchids
- Whiteflies. They are small flying insects of white color that are located on the underside of the leaves and feed by sucking the elaborate sap. Its activity generates molasses on the leaves of the plants on which a black fungus called “Fumagina” develops. Their danger lies in the fact that they weaken the plant by extracting the elaborated sap and that they are vectors that transmit viruses. We can fight it with the following active materials: abamectin + pyrethrins, rapeseed oil, orange oil, paraffin oil, acetamiprid, alpha cypermetrin, azadiractin.
- The spider mite. The spider mite thrives in mediums with low relative humidity. Symptoms are small silver dots due to bites. The treatment involves two fumigations, the first with abamectin + hexitiazox and the second with abamectin + Ethoxazole.
- Aphids. Like the whitefly, aphids feed by sucking the elaborate sap. It is fought with cypermetrin, Deltametrin, lambda cihalotrin, Esfenvalerato and pirimicarb.
- Mealybugs. They are very easy to distinguish since they are coated witha waxy and whitish substance that gives them a cottony appearance, hence they are known as “Cotonet”. The worst damage is caused to flower buds. If the infestation is little we will take them off with a cotton swab soaked with burning alcohol, but if the infestation is serious the recommended active substances are: Paraffin oil, Acetamiprid, Spirotetramat and Sulfoxaflor.
- Snails and slugs. The damages are easily recognizable and metaldehyde-based baits are used for their control.
The diseases of orchids We have left for the last what for every grower of any type of plants is more complicated to fight and are the diseases caused by fungi, bacteria and viruses. Before seeing howtofight these diseases we will give some tips to prevent their appearance in our plants:
- Avoid wounds on any organ of the plant, as it is the main gateway for pathogens.
- Maintain an adequate fertilization program, avoiding both the nutritional deficiencies that lead to weak plants, as well as excess nitrogen.
- Ensure optimal ventilation to the plants by separating them properly.
- Control relative humidity.
- Perform a good frequency of watering, taking into account that it is better to fall short than to overdo it.
- Promote good drainage of the pots.
- Avoid growing in very clay soils.
- Frequently wash and disinfect gardening utensils with 1-2% sodium hypochlorite.
- Remove waste from affected plants.
- Choosing the most tolerant and disease-resistant varietiesis.
- Periodically disinfect irrigation water.
- Disinfect substrates and pots with some of these active substances: chloropicrin, dichloropropene, metam-sodium or carbon disulfide.
- Use copper-based products preventively, such as Bordeaux broth and copper sulfate.
- With viruses, the only thing we can do is prevent their entry by controlling insect vectors (aphids, whiteflies and thrips).
- Diseases caused by fungi. Due to the high relative humidity required for cultivation, orchids can be attacked by various phytopathogenic species. The symptoms are rots, watery or dry, of various shades that affect the rods, stems, roots, pseudobulbs and leaves.
- Black rot. Pythium and Phytophthora are the two main genera of oomycetes that cause significant damage to orchid farming. Once the zoospores penetrate the plant tissue the infection progresses rapidly with the visible signs of infection being small, watery and translucent spots that expand rapidly and change to brown and then to black in leaves, pseudobulbs, stems andraíz; the plants weakenton and grow slowly as they progress, or they may have yellow leaves and even premature fall of these. If the affected plant is not treated, it can infect others in a very short time. Young orchid seedlings are highly susceptible to infections caused by Phytophthora species, mainly P. palmivora and P. cactorum. Attacks by Pythium are less frequent in orchids.
Once the affected plant we will isolate it and remove the affected parts. To combat the fungus we will use fungicides and the most effective are metalaxyl and etridiazole.
- The gray rot. It is caused by the pathogenic fungus Botritis cinerea and is a widespread disease. Botrytis in orchids only affects the flowers and circular spots appear on the petals of pinkish color at first turning later to brown color; the spots progress rapidly causing total rotting of the flower. High humidity and temperatures around 20 ºC favor infection. In the article dedicated to the damages produced by this fungus in cannabis you have a protocol of action with various active materials.
- White rot. The causative agent of this phytopathology is the fungus Sclerotinia and manifests itself in the form of oily spots on the leaves. Later the plant begins to wither and is covered with a whitish layer with small grainy black spots. It is necessary to act quickly so that the plant does not die and the recommended active substances are propiconazole, iprodione, chlorthalonil and methyl-thiophanate.
- The leaf spot. The fungus Phyllosticta is the cause of this disease that produces yellow spots on the leaves and then progresses to a darker color. If the plant is not treated, it can die. The active substances used are Folpet and Difenoconazole.
- Anthracnose. The causative agent is the fungus Colletotrichum, one of the most common genera of fungi that cause spots and blight on the aerial parts of plants. This genus of fungi occurs most often in tropical and subtropical climate regions, although some species may proliferate in temperate climates. These phytopathogens mainly invade the injured or weakened tissues of plants. The symptomatology presents as circular leaf spots, well defined and depressed, with the center of dark color and surrounded by a diffuse halo of light brown coloration. With the progress of the disease, the spots grow and come together to form larger necrotic areas. The recommended active substances are pyrimethanil and pyrimethanil + imazil.
- Vascular mycosis: Fusarium spp. It is a very common disease in orchids and initially penetrates through healthy roots and subsequently colonizes vascular tissue, causing widespread wilting, foliar chlorosis and necrosis of the aerial part of the plant. This pathogen infects plants when they are young and the severity of the disease depends on the age of the infected tissue and humidity levels. Young plants die quickly when infected by the fungus while surviving plants continue to be affected, destroying new growth and not blooming when they reach maturity. The active substances recommended to fight against the fungus are Metalaxil, Fludioxonila and Fluopiram. You can learn more about this disease in the article on the damage of fusarium in cannabis.
- Diseases caused by bacteria. Themost common symptoms of diseases caused by bacteria in orchidsare rots and soft leaf spots, since these plants are succulent, have thick tissues and an abundant water content, constitute an excellent culture medium for the growth of bacteria. The main species that parasitize orchids are Pseudomonas aeruginosa and Erwinia carotovora. Pseudomonas is less common and symptoms are a necrotic spot at the base of the rhizome or pseudobulb that begins as a cream coloration before generalizing as a brown or black rot. On the leaves and even on the flowers there are small black spots or lesions of moist appearance and with watery halos. Another characteristic is the presence of air inside the affected organs and destroyed especially in the pseudobulbs, due to the production of gas by the bacteria. Bacterial rot begins at the roots and ascends to the aerial part.
Erwinia carotovora produces the so-called “soft rot or mild rot” and can affect all the organs of the plant, spreading and rapidly. It begins as brown or black spots of appearance húmeda, which when growing form a rot of soft consistency, evolving to a necrosis of the tissues with an unpleasant smell. The bacteria penetrate the plant mainly through wounds and spread
As we have seen at the beginning, better to fight against bacteria is prevention and for this we have the good cultivation practices described above and the use of preventives such as copper sulfate, cupric hydroxide, Bordeaux broth, and antibiotics such as oxytetracycline and streptomycin.