Pests and diseases of orchids

The pests and diseases of orchids were studied by Dr. Zsuzsanna Némethy ny. Assistant Professor, Plant Protection Consultant at www.novenydoktor.hu presents:

Many animal pests of orchids are known, most of which can and do infect many other ornamental plants.

Shield lice
Tiny animals, 1-2 millimeters in size, all species suck and feed on the sap of plants. The leaves are distorted by suction and die by a strong infection. Under room conditions, several generations of them develop each year, very prolific animals. Sticky honeydew is selected, its brilliance dripping on the surface of the plant or dripping to the floor is eye-catching. Their young larvae move on the plant and spread the pest. Room airflow can also move it to neighboring plants. Adult shield lice usually no longer move. Waxy shield lice form a whitish cotton-like wax coating on their backs, which can be recognized from this. In turtle shield lice, a hard shield of different colors protects the animals attached to the plant.

Due to their hiding individuals living in plant corners, they are difficult to eradicate, usually spraying 3-5 times gives only adequate results. Due to its concealed individuals, a satisfactory killing effect is given by the absorbed insecticides: for example, Actara, Mospilan. Before spraying, it is advisable to move the shields off the plant with a soft brush and shower with lukewarm water. This helps the insecticides to come into direct contact with the animal and to have a killing effect.

Tiny, around 1mm, elongated, cylindrical animals, adult individuals have 2 pairs of wings. Sucking pests, as a result of their sucking, a silvery-colored, irregularly shaped discoloration of barely visible size is formed on the leaves and green parts of the plant. The attacked buds and flowers are distorted. During their development, several larval forms alternate that do not have wings. They often live in the soil at the base of the stem for a longer or shorter period of time, these individuals survive the spraying and re-multiply when re-established on the plant.

Chemical control can only be effective with multiple (3-4 x) repetitions. Among the free insecticides, Mospilan, Decis, Match and Actara are effective against it.

Spider mites
The spider mite, both living and damaging in the open air and in the home, is also a small, barely visible to the naked eye, 4 pairs of legs (spider-like) insect, living on the back of the leaves, often forming a cobweb-like web. It is a sucking oral pest, it likes the youngest leaves at the end of the shoots of the plants, they tend to multiply on them en masse. After a large number of puffs, the leaves turn silvery in color, then turn yellow, and eventually die brown. It only grows in an apartment with hot and dry air.

It is often sufficient to wipe the mite leaves with a damp cloth and then gently spray the back of the leaves with water during the day. Only special acaricides are effective against them: Floramite, Flumite, Nissorun, Sanmite, Omite.

Thin-leafed orchid species are mainly infected, they grow on young, young leaves. Sucking pests, many generations of them develop every year, they are constantly multiplying in flats, distorting the leaves, distortions and small deaths appear on them. Honeydew is selected, on which ants feeding on honeydew prefer to settle.

Insecticides against aphids: Biola, Bioplant Flora, Vectafid-A, Biosect, Talstar, Karate, Decis, Teppeki, Chess, Pirimor, Actara, Mospilan

Both married and unmarried snails can also damage orchids by chewing. Snails prefer constantly wet, wet places, they pull there. They are active at night and often cannot be found during the day as they hide in the soil or in a special orchid growing medium. They are killed by snails containing the active ingredient metaldehyde, but they cannot be used in the home. In potted orchids, the snails must be found and mechanically destroyed. For outdoor orchids, dehumidifiers scattered around the pots are also effective: animals climbing through them (lime powder, powdered fertilizer) die as a result of dewatering.



Viral diseases
Diseases caused by viruses are of the greatest importance. Plant viruses are very small parasites that live in plant cells, organisms that parasitize plant metabolism and spread to all parts of the plant. Plants that are already infected remain infected with the virus for the rest of their lives and cannot be cured. The offspring and reproductions of infected plants are also infected with the virus.

Many ways of spreading viruses are known: they are spread by aphids, shield lice, and they are also spread by pollen from virus-infected flowers. Infected growing media, pots, or irrigation water dripping from an infected plant can also be a source of infection. It is most often spread by the cutting tool during nursing work: the virus particles in the plant sap adhering to the knife or scissors get into the damaged cells on the cutting surface of the next plant, infecting the plant. Progeny propagated from a virus-infected plant will also all be viral. Pollen from the virus-infected plant also spreads the virus, so it is recommended to monitor the health of the pollinating plant when pollinating.

Prevention is based on prevention! Make sure that the newly acquired orchids are virus-free, as evidenced by the plant passport (phytosanitary certificate). For care work, continuously disinfect the cutting tools by soaking in a 1: 5 solution of Hypo sold for household use for 1-2 minutes. Metal devices can also be effectively disinfected by dipping in alcohol and subsequent burning. We can ensure that plastic pots and trays are kept clean by washing them with a hypo solution. Along with diseased plant parts adhering to pieces of tree bark, virus particles can also be effectively killed by keeping them at 90-100 degrees Celsius in an oven for 30 minutes. Efficiency is enhanced by high humidity, water vapor. Higher than recommended temperatures already damage the bark, so its use is not recommended.

Viruses can also be spread in the event of damage during treatment with plant sap. As a precaution, wash your hands thoroughly with conventional soap (preferably laundry soap) when caring for plants.

Viral infection can usually be recognized by characteristic symptoms. Irregular discoloration other than green base color is observed in the mosaic pattern. Yellowish line or ring-shaped drawings later turn brown. In the thick-leafed Phalaenopsis species, the patterns sink into the leaf flesh. There may also be a change on the flowers: the color characteristic of the variety changes, drawings and spots of different shades from the base color develop on the flower petals (color refraction).

Recognition of viral disease is complicated by the fact that the development of symptoms is also influenced by temperature and plant condition. At high temperatures above 25 degrees Celsius, the symptoms fade and disappear, and even in vigorous plants kept under optimal conditions, the viral symptoms are faint and barely noticeable. Based on symptoms, it is not possible to identify the pathogenic virus. The fact of viral infection can only be established by a laboratory test. Special laboratories with antisera of plant viruses carry out the determination of viruses.

Common viruses infecting cultivated orchids and how they spread:

Viruses infecting orchids only:

Odontoglossum ringspot virus (ORSV) with cutter, propagating material
Cymbidium mosaic virus (CyMV) with cutting equipment, propagating material
Orchid fleck virus (OFV) propagating material

Many viruses that infect cultivated and cultivated plants:

Tomato spotted wilt virus (TWSV) with thrips, propagating material


Bacterial diseases
Bacteria infecting plants are characterized by their growth and infection under wet, humid conditions. Where the maintenance and care of plants is not carried out professionally and the pathogen enters the plant population, it causes severe destruction. Bacteria infecting the plant are unicellular, can be examined with a light microscope, have cilia (protrusions), they can be used to move in water, they are able to move actively. This explains that their condition of existence is the wet environment. They also spread with water dripping during care. Their symptoms are: usually watery, softening spots that grow and spread quickly, the spots eventually turn brown and then turn brown and blacken. It is common for infections to start with injuries. Pseudomonas species cause minor leaf spot, while Erwinia bacterial species cause rot. All of the currently marketed pesticides are effective against bacteria. Of the copper sulphate, copper oxychloride and copper hydroxide active substances, Champion and Kocide, the least toxic to the plants, are recommended. Copper-containing products prevent the spread of bacteria, but they do not cure the diseased plant parts, they cannot prevent the growth of the pathogen entering the plant or its internal damage. It is recommended to transplant the plant into a new, not yet used growing medium.

Fungal leaflets also occur on the leaves of orchids. They are different in size, shape and color. They do not usually cause the destruction of plants, but they weaken them. By spraying the leaves 2-3 times a week, their foliage can be cleared.

Fungicides for stain diseases: Amistar, Dithane, Kocide, Champion.

Botritic flower petal spot
In plants kept at permanently high humidity, when water droplets precipitate on the flower, the appearance of botrytis petal spots is common. 1-2 mm watery and then gray-coated spots develop on the petals, which dry out brown after drier conditions. Improper housing conditions should be avoided. Chemical intervention is rarely required.

Root rot
Pathogenic root rot is not uncommon in orchids. His symptoms appear slowly, with a delay, often when the roots are almost completely destroyed. It can be caused by a number of fungal species that cause root and seedling death in other plants as well. These are: Phytophthora, Sclerotinia, Pythium, Rhizoctonia species. The roots of the plant highlighted from the pot are brown, soft, hanging loosely. Remove the dead roots of the plant, soak the remaining roots in a 0.2% Topsin M 70. fungicide solution for 20-30 minutes: After drying the roots for 2-3 hours, transfer to a new medium. For the next 3-4 weeks, watering very sparingly, at a reduced dose and less frequently.

General principles for the use of plant protection products
In the case of individual pests, I recommended only among the plant protection products that are in free circulation, so they can also be bought and used by lay people.

Pesticides, like drugs, are poisons, although they have varying degrees of toxicity. Their use is only recommended outside the apartment or in a building where no human or animal is present. A detailed description of the use of plant protection products can be found on the packaging. Before opening, read in detail, study the requirements of the license document! The products may be toxic to the skin or by inhalation, it is recommended to wear the required protective equipment.

What to do when a new orchid plant enters?
Most pests come with the newly introduced plant into the apartment, the collection. It is advisable to keep the new plant in quarantine for 3-4 weeks, separate from other plants, preferably in another room. During this time, it is thoroughly examined weekly with a hand magnifier, including the color and back of the leaves, the base of the leaves, the intersection of stem and soil, and the soil. Before placing among the other plants, spray thoroughly with a mixture of Actara (2 g) and Amistar (1 ml) dissolved in 1 liter of water. Irrigate with the remaining spray solution instead of water.

I suggest a similar treatment when relocating plants outdoors to the home in late summer.

                                                                                     Dr. Zsuzsanna Némethy
                                                                                     assistant professor