Pest and disease control methods and key technical points for orchids

Pests and diseasesControl is also an important part of orchidcultivation. If control is not carried out in time, the introducedpests and diseaseswill run rampant and inevitably cause unnecessary losses. Inorchidpest and diseasecontrol work, the principle of "prevention first, integrated control" should be followed. Newly purchased orchid plants must be strictly inspected. Once pests or diseases are found, they must be isolated and treated, and must not be placed together with other healthy orchid plants until the pests and diseases are cured. Common orchid pests and diseases include the following: 1. Diseases (1) Leaf spot disease - mostly seen on Cattleya plants. In the early stage of infection, small black spots appear on the leaves, surrounded by water-soaked yellow halos, which later become round or oval lesions. This disease is mostly caused by excessive humidity. Control method: Improve ventilation conditions, reduce humidity, immediately cut off diseased leaves, and spray with 1% Bordeaux mixture. (2) Anthracnose - mainly harms orchid leaves, with large-floweredCymbidiumbeing the most susceptible. The causes are mostly poor ventilation and muggy heat. The symptom is the appearance of oval lesions on the leaf surface, changing from yellow to black, and in severe cases the entire leaf turns black. Control method: Cut off diseased leaves, strengthen ventilation and reduce humidity, and spray with carbendazim, chlorothalonil or thiophanate-methyl at 500 times dilution, then spray once every 10 to 15 days thereafter. (3) Stem rot - a common and serious disease. This disease often occurs at the base of the stem, then spreads to the roots and leaves, and in severe cases the entire plant dies. Control method: When this disease is found, watering should be stopped immediately, and the orchid plant should be exposed to sunlight. Spray with 1% Bordeaux mixture or zineb at 600 times dilution, or chlorothalonil at 500 times dilution. (4)Soft rotdisease - mainly harms Cattleya and Phalaenopsis. In the early stage, water-soaked green spots appear at the leaf tips, as if scalded by hot water; the leaf tissue becomes water-filled and rots, accompanied by a foul odor. Control method: As soon as it appears, cut off the diseased leaves, sprinkle charcoal powder on the wounds or apply chlorothalonil powder for disinfection, then spray the plant with 1% Bordeaux mixture. (5) Brown rot - mainly harms Paphiopedilum. The disease develops extremely quickly; by the time you notice it, the plant has already rotted at the core and died, with the whole plant turning black and the leaf tissue becoming mushy. Control method: Immediately stop watering, cut off the diseased plant, disinfect the wounds with charcoal powder or chlorothalonil powder, then spray with 1% Bordeaux mixture. (6) Flower rot - most common on Cattleya. This disease easily occurs during the main flowering period when the temperature inside the greenhouse is high and the temperature outside is low. At first, small brown spots appear on the petals, then the spots become larger and more numerous, but the disease is confined to the flowers only. Control method: If a sudden temperature drop is forecast before flowering, immediately reduce the indoor humidity and immediately spray lime sulfur mixture to prevent flower rot from occurring. (7) Rust disease - first appears on the leaves, producing yellow-brown powder. This disease easily occurs under low temperature and high humidity, and is most common on Cattleya, Phalaenopsis, Vanda, Dendrobium and large-floweredCymbidium. Control method: When watering, be careful not to wet the leaves. If watering on cloudy and damp days, strengthen ventilation. After cutting off diseased leaves, spray with 1% lime sulfur mixture. (8) Viral disease - a difficult disease to cure. Viral diseases are transmitted by sap-sucking insects such as aphids. In the early stage, the leaves and flowers turn yellow, then become black spots or streaks, and subsequently the leaves and flowers shrivel. Control method: Once a diseased plant is found, immediately discard it by deep burial to prevent transmission. There is currently no specific drug to treat it. 2. Insect pests (1) Scale insects - the pests that harm orchids the most. They mostly occur under conditions of high temperature and high humidity with poor ventilation. The insect body attaches to the plant, protected by a waxy shell on the outside, and lives by sucking sap. In severe cases, they cover the entire plant, causing the orchid plant to shrivel and die. Control method: Improve the ventilation environment, and spray with 40% omethoate at 1000 times dilution or 5% malathion at 800 times dilution. For a small number, they can be wiped off with a small brush dipped in soapy water. (2) Red spider mites - often gather in groups on the underside or upper side of leaves to suckorchidsap, causing the affected parts to become yellow spots, affecting the appearance and growth of the leaves. Control method: Spray with tetradifon at 1000 times dilution; if using 40% omethoate liquid added to 800 times water, the effect is better. (3) Aphids - the aphids that harmorchidsmostly carry out their activity during the flowering period, moved by ants to flower buds or juicy parts of petals to suck sap, and the honeydew they excrete is eaten by ants. In severe cases, the flower buds cannot open, and the flower color becomes dull. Control method: Use 20% dimethoate emulsifiable concentrate at 500 times dilution, or use 50% dichlorvos stock solution mixed with 300 times water for spraying. For a small number, they can be wiped off with a cloth. (4) Bagworm - uses a self-woven silk "bag" as cover, crawling on orchidflowerleaves to gnaw on the leaves and flower buds. It mainly harms orchids with juicy leaves such as Cattleya. Control method: Catch and kill immediately, or spray with 50% dichlorvos mixed with 300 times water. (5) Leaf miner - the larva of the leaf-mining fly, which gnaws on the leaf flesh beneath the leaf epidermis, leaving an obvious "tunnel" where it has fed, forming a white line band on the leaf surface, and in severe cases can cause the entire leaf to necrose. Leaf miners mostly occur on the leaves of Paphiopedilum. Control method: When this insect is found, if there are only a few, use a needle to pick them to death. If there are many, spray with 40% omethoate at 1000 times dilution. (6) Snails - a kind of mollusk that hides by day and comes out at night. During the day they often lurk in the gaps at the bottom of pots, and at night they come out to gnaw on the young shoots and flowers of orchid plants, makingorchid growingextremely troublesome. Control method: For a small number, catch and remove them during the day or at night. Scattering lime powder around the pot can prevent them from climbing onto the plant to gnaw. When there are many, place rotten vegetable leaves around the orchid pot as bait, so that when the snails crawl into the rotten vegetable leaves to feed, they can be caught and removed one by one. Li Shaoqiu, Hu Songhua