Orchid Medication, Part Four: Getting to Know Agricultural Streptomycin

Around Qingming and through the moldy rainy season, as well as around Mid-Autumn, is thesoft rotdisease peak period, and many who have experiencedsoft rotdisease find it nothing but a headache.soft rotdisease is also called bacterial soft rot, and its pathogenic bacteria are Cattleya monocystis, Erwinia, and others. It is a disease that harms the root and stem parts of plants, and is easily triggered by high temperature and high humidity. Let us understand what bacteria are: bacteria belong to prokaryotic microorganisms, referring to a class of microorganisms in which there is no obvious nuclear membrane between the nuclear material and the cytoplasm, and whose chromosomes are composed of a single nucleic acid. Prokaryotic cell-type microorganisms include bacteria, actinomycetes, and cyanobacteria. The process by which bacteria harm plants: bacteria mainly produce toxins, causing plant rot or tissue death, or blocking and destroying vascular bundles, forming tumors. Because bacterial control is relatively difficult, the best control method is to prevent the occurrence of the pathogen. General manifestations of bacterial soft rot: it affects the whole plant, mostly infecting from the root-stem area or wounds, entering the vessels and then lying dormant, only causing disease when conditions are suitable. When leaves are affected, dark green water-soaked small spots appear, rapidly expanding into yellow-brown softened rot. Brown water droplets often seep from the rotting area, with a special foul odor, and in severe cases the leaves quickly turn yellow. If the pseudobulb is infected, water-soaked lesions also appear, brown to black, ultimately making the pseudobulb soft, shrunken, and dark, rapidly rotting. This disease is hidden and sudden; if not treated promptly, it spreads extremely easily, and generally infected plants are basically beyond saving. By using the antagonistic effects among microorganisms, certain special substances produced in the life activities of beneficial microorganisms inhibit the growth and reproduction of disease-causing bacteria; such substances are called "antibiotics." For example, "agricultural streptomycin" can control bacterial soft rot. Agricultural streptomycin is a metabolic product produced by actinomycetes, with a broad bactericidal spectrum, especially effective against many bacterial diseases (it also has control effects on fungi), has systemic action, can penetrate into the plant body, and be transmitted to other parts. It is low in toxicity to humans and livestock, and its toxicity to fish and aquatic organisms is also very small. It is mainly used for spraying, and can also be used for root drenching and seed soaking disinfection, etc. Issues to note in the application of agricultural streptomycin: biological pesticides kill insects and bacteria more slowly than chemical pesticides in the lethal process, so early control should be advocated, that is, spraying at thepests and diseasesinitial stage of occurrence. Most biological pesticides decompose when exposed to strong sunlight, reducing their efficacy, so spraying should be chosen in the afternoon or on cloudy days, and if it rains after application, spray once more. Strictly follow the application dosage; do not arbitrarily increase or decrease the application concentration. The product name of agricultural streptomycin is usually "agricultural streptomycin sulfate," usually a 72% soluble powder; the technical material is a white amorphous powder, easily soluble in water, insoluble in most organic solvents. Under cool and dry storage conditions, the stable period is more than two years. General small packages can be divided into 10 million units and 5 million units, with weights mostly between 7 and 15 grams. The control targets registered for use by the Ministry of Agriculture for agricultural streptomycin are: Chinese cabbage soft rot, rice bacterial leaf blight, cotton damping-off, cucurbit downy mildew, etc. It can be used in the control oforchidsoft rot, spraying once every seven to ten days during the control period, for three to five consecutive sprays, which can prevent bacterial diseases. The dosage used in vegetable control (72% soluble powder) is 3500-6000 times, while the orchid community generally uses 2000 times (the main parameter of the ratio is the unit of measurement of actinomycete metabolic products). (Gao Haiyong)