Orchid Pest and Disease Control Methods and Technical Key Points
Preciousorchidvarieties were monopolized by a small number of feudal scholar-officials and the bourgeoisie in the old society, and after wars and turmoil, many famous varieties were lost. After Liberation, the Party and the People's Government attached great importance to cultivatingorchids. In addition to cultivation in public gardensCultivation, a great many orchid enthusiasts also very much enjoy growing them. Butorchidsare not as easy to grow as ordinary flowers, and are prone to attack by externalpests and diseases. Moreover, because growers lack scientific knowledge and experience, they lack a systematic understanding of the causes ofpests and diseasesand control methods, and sometimes by the time they realizepests and diseasesare present, they do not know how to deal with them, causingorchid plantsto suffer spreading infestation and severe losses. The following is a listing based on the various situations and control methods the author has encountered over many years of practical operation:
(1) Diseases
Orchid diseases are mainly caused by poor ventilation, high temperature and humidity, or prolonged rainy weather. Under the influence of these adverse conditions, orchid plants grow poorly and are easily infected by airborne pathogens or diseases from other nearby plants, invading through leaf stomata or wounds. Common diseases include:
Black spot: The symptom initially appears on the leaf surface as round dark brown spots about 2 or 3 mm in diameter, which then gradually expand and increase in number; in severe cases they spread from a localized area to the entire tissue, causing the leaves to lose their ornamental value and the orchid to grow poorly.
Control method: Strengthen ventilation, reduce humidity, and try to keep the leaves dry. Or spray the leaf surface with Bordeaux mixture. Cut off and burn all severely affected leaves.
Southern blight: This is a disease caused by fungi. It mostly occurs during the rainy period at the turn of summer and autumn, at the base of the leaf sheath and beside the pseudobulb, where a layer of white spiderweb-like mycelium spreads; it can cause the orchid plant to die very quickly.
Control method: Once discovered, quickly remove the mycelium and spray Bordeaux mixture and nicotine sulfate solution to sterilize. Then isolate the affected plant. Strengthen ventilation and light penetration.
Brown rot: This is a bacterial disease. It mainly occurs on new leaves and new pseudobulbs. In the early stage of the disease, water-soaked spots first appear on their leaves or pseudobulbs, then turn light brown, gradually becoming dark brown; the surface of the affected area becomes wrinkled, and a water-soaked halo appears around the edge. This disease develops extremely quickly; often a plant is affected in the morning and by evening the affected part has turned yellow-white, and by the next day the whole plant or entire pseudobulb is endangered, becomingsoft rot-like. It mainly occurs from late spring to early summer.
Control method: Quickly repot and change the soil, cut off the diseased part or the whole plant, and burn it immediately. Then disinfect the cut surface with sulfur powder or mercuric chloride water. Isolate temporarily, and spray with a 1:1000 mercuric chloride solution or a dilute nicotine sulfate solution for disinfection.
Black virus disease: This is a disease transmitted by a type of aphid. At first, yellow spots appear on the leaves, which then become black spots or streak-like markings.
Control method: Keep theorchid-growingarea clean and hygienic, and frequently pull up surrounding weeds. Strengthen disinfection. If there are too many affected areas, cut them off and burn them.
(2) Insect pests
Orchid scale insect: Commonly known as orchid lice, it is one of the most common and widespread pests harming orchid plants. This scale insect is covered with a flat, round, earth-brown waxy shell, about 0.1 cm in diameter, flea-shaped, attaching to both sides of the leaves or inside and outside the leaf sheath. The insect uses its thread-like mouthparts to suck the nutrient fluid from within the leaves. After scraping off the insect bodies, pale yellow marks appear on the leaf surface; if they cluster densely, the affected part gradually turns yellow, growth weakens, and in severe cases the plant gradually withers and dies.
Control method: A simple method is to use a palm brush or a relatively soft toothbrush to gently brush them off along the leaf veins in the longitudinal direction (if too much force is used, brush marks may be scratched on the leaves, or the leaves may even be broken). You can also gently scrape off the insect bodies with a fingernail. Or use medicinal cotton dipped in diluted nicotine sulfate solution, or lime-sulfur mixture, to wipe the leaves. However, the few leaves at the center of the leaf cluster are relatively tender; when wiping, use two fingers of one hand to pinch the base with moderate pressure, and two fingers of the other hand to hold the cotton moistened with the solution, clamping it on both sides of the leaf, and wipe upward along the leaf. This must be done carefully, otherwise the central leaves are often pulled out or broken off.
In addition to killing them with the above-mentioned solutions, strengthen ventilation and light penetration in the daily orchid-growing area, and avoid an overly humid surrounding environment.
Ants
Orchid roots are fleshy roots that store a certain amount of water and are slightly sweet in nature; the surrounding soil is loose, so ants are often attracted to build nests in the potting soil, making the soil loose and affecting root absorption.
Control method: According to the ancient Chinese way of growing orchids, a shallow bowl is filled with water and the tripod-footed orchid pot is placed in it (the bottom hole must not be submerged) to prevent ants from entering. If an ant nest is found in the pot, repot and change the soil immediately, or place sweet, fragrant, oily food around the pot to lure the ants out and capture and kill them gradually. You can also immerse the orchid pot in water and let water seep in through the bottom hole to drive out and drown the ants. In addition, some DDT powder can be sprinkled on the pot stand to prevent ants from entering the orchid pot.
Mosquitoes and flies
The orchid-growing area is relatively shady and damp, easily breeding mosquitoes and flies; this not only hinders workers from concentrating on their tasks, but fly droppings also pollute the leaf surface and are very unsightly. Moreover, mosquitoes and flies easily carry various pathogens, causing infection and other diseases.
Control method: Clear away surrounding weeds, garbage, and other materials; fill in nearby low-lying areas and stagnant pools; or turn upside down unnecessary water-holding containers to reduce their breeding grounds. Keep fish in the watering tank to keep the stored water free of larvae. Regularly use chemicals to disinfect the surrounding environment.
Earthworms
The environment around the orchid stand is shady and damp, easily breeding earthworms. Especially during the rainy season, earthworms often crawl up onto the orchid stand and burrow into the soft potting soil, wriggling about and feeding on nutrients, making the surface soil layer loose and disordered, with piles of worm castings everywhere; this is not only unfavorable to orchid root growth but also unsightly. If these conditions are found, use fine lead wire or bamboo skewers to pierce into the soil to lure out the earthworms, and catch or kill them one by one. You can also immerse the orchid pot in water for a moment to drive them out and catch them one by one. To eliminate this problem, regularly spray BHC powder around the orchid stand posts and frame to kill or drive them away on contact.
Red spider mite
This mite is small in body and vermilion red in color, often densely clustering on both sides of the leaves, sucking the sap or epidermal tissue from the leaves. After being affected, in mild cases the leaf surface tissue becomes rough or mottled; in severe cases the leaf mesophyll dries up and the plant gradually dies.
Control method: Use medicinal cotton moistened with dilute dimethoate or derris extract solution to wipe them off gradually.
Caterpillars
These are the larvae of butterflies and moths, of which there are many species. They often lodge on trees around the orchid stand, gnawing on leaves, and when blown by the wind they drift and fall near the orchid stand, then crawl up onto the orchid stand and into the potted orchids, damaging orchid leaves, flower buds, and so on.
Control method: Regularly spray insecticide solution on the surrounding trees, or catch and kill them directly.
(3) Animal damage 1. Cat urine and feces
Domestic cats often like to urinate and defecate in the surface soil of potted orchids, and afterward use their claws to turn over the soil to cover it, disturbing the pot surface; soaked with this cat urine and feces, orchid roots rot very easily. Also, before a domestic cat becomes pregnant, it is extremely fond of gnawing on young tender leaves, and orchid leaves are no exception.
Control method: Drive them away at any time or train them not to gnaw the leaves.
Bird damage
Because orchid roots are soft and slightly moist, sparrows often like to take dust baths in the soil, rolling about and disturbing the potting soil so that orchid roots and pseudobulbs are exposed, or injured as a result.
Control method: Insert several small colored cloth flags among the pots; as they flutter in the wind, they frighten the birds so they dare not approach.
Snail and slug damage
Orchid-growing areas are mostly shady and damp, extremely favorable for the survival of snails and slugs; during the day they hide in dark piles of bricks and rubble or under pots, in crevices, and under nearby shady wells and water tanks, and at night they emerge in groups to crawl about searching for food. Besides gnawing on young tender new leaves, wherever they pass they leave a sticky, silvery-white secretion that can affect orchid leaves.
Control method: At night, set up a light to lure and catch them and kill them, or after catching them put them in salt water to kill them. Clear away surrounding garbage and green grass so they have nowhere to hide. Or scatter BHC powder around the orchid stand posts and frame to prevent them from crawling up.
For the many pests and diseases mentioned above, besides using appropriate chemicals to kill or drive them out on contact, maintaining environmental sanitation in the surrounding area so that pests and diseases cannot survive, and strengthening daily management to promote strong roots and lush leaves and increase resistance, are also measures that must not be neglected to avoid diseases. When exchanging varieties or purchasing new ones, you must pay attention to whether there are any pests or diseases; after bringing them back, it is best to first carry out disinfection and preventive work. If pests or diseases are found and cannot be controlled, they should be burned immediately to eliminate future trouble.