Symptoms and Control Methods of Orchid Root Rot

The root rot pathogen belongs to Rhizoctonia solani (Rhizoctoina solani), which mainly inhabitscultivationmedia, and in environments with suitable temperature and humidity, it damages the root tissue of Chinese orchids, leading to a reduced ability of the roots to absorb water and nutrients. Transpiration and absorption become uncoordinated, the orchid plant gradually weakens, and normal growth is affected. The root rot pathogen mainly infects the root system, and the affected orchid roots initially show brown lesions, sunken areas, and necrosis. In severe cases, several lesions will form a ring encircling the stem base and newly grown roots or root system, and finally the entire root rots. This further impedes water transport and support, and the orchid plant gradually develops conditions such as wilting or yellowing, and stunting. The root rot pathogen mainly damages root tissue and cannot ordinarily be detected by the naked eye. Except when cultivation managers routinely remove the orchid plant to observe it. When the root tip or root system rots, the orchid plant grows slowly, leaf tips scorch, leaves wilt, bracts turn black, and only after the newly grown roots turn black does one look for a solution, but by then it is already too late! Great harm has already been done to the orchid plant's subsequent growth. Therefore,cultivationmanagers must ordinarily pay more attention to whether the sphagnum moss has died, whether the medium has acidified, whether the medium has good permeability, whether chemical fertilizers have been applied improperly, whether watering is excessive, whether the air in the orchid room circulates and convects, whether the medium is clean and free of pathogens, whether the medium has been fully piled and fermented before use, and whether chemical control is thorough; whether the plants have been disinfected when planted,cultivationand whether pest control has been carried out during management, etc. Most importantly, whether the planting medium is appropriate. These problems are all causes of root rot, and cultivation managers must be cautious. Transmission routes: Root rot is a medium-borne disease. It mainly survives unfavorable environments as dormant mycelium or sclerotia. In the cultivation media used for Chinese orchids, it has been detected that a certain medium carries this pathogen, and cultivation managers need to pay attention to what they use. It occurs most severely in old media that are overly wet and poorly aerated, especially expired old media, and sometimes the entire root system of the whole plant rots. Control calendar: (1) Firmly change the medium once every one to one and a half years, choosing an excellent medium with half of each particle size, good aeration, strong water retention, moderate pH, good buffering capacity, light texture, and clean, non-toxic quality. (2) Before use, the medium should first be fully piled and fermented for six months, so that the content of toxic powder-type compounds decreases and beneficial phenolic compounds are synthesized to promote orchid growth. The high temperature generated during piling can kill pathogens, nematodes, and other important factors affecting Chinese orchid growth. After piling, beneficial microbial populations will certainly increase greatly, reducing soil-borne diseases such as sclerotial disease, disease, and root rot, and promoting root growth in a healthy medium environment. (3) During medium piling, Jiandian 18 may be added, or it may be added after planting, which can inhibit the root rot pathogen and has a very significant effect on root growth and development. (4) Regularly test the pH value of the medium and the base salt concentration. For pH testing, the following can be used: (A) Saturated paste method. The ratio of medium to distilled water is 1:3. After stirring for one hour, measure with a S47TEXPHmeter; (b) Base salt concentration testing method: the ratio of medium to distilled water is 1:3. After fully stirring for one hour, measure with a HananH18820Ecmeter. If the pH value is too acidic and the base salt concentration is lower than 1.0, it is necessary to supplement dolomite lime and phosphate fertilizer. Also strengthen fertilizer supply and apply phosphate-solubilizing bacteria to facilitate root group growth and stem and leaf development. (5) Ordinarily pay attention to damage by root mites, root thrips, nematodes, cockroaches, and other insects. (6) Apply beneficial microbial additives to achieve the control effect of inhibiting and resisting bacteria. (7) After planting, during the early stage of new shoot growth, supply an appropriate amount of phosphate fertilizer and Huagenwang to promote rapid root growth, and to promote earlier root emergence and the function of leaving the mother plant to live independently, so that the root system develops vigorously and the plant grows strong. (8) Regularly apply 75% Miepuning wettable powder diluted one thousand times. (9) When diseased plants are found, the medium should be changed immediately. Before planting the orchid plant, the rotted root system must be cut off. The medium must first be piled and fermented. After planting, immediately use 75% Miepuning wettable powder at one thousand times to drench the medium and root system. After planting, move it to a cooler place, and every three days apply amino acid at two thousand times as a foliar spray, so that because photosynthetic capacity is insufficient, the nutrients needed to grow new roots are supplied by the decomposition of stored substances in the plant cells, thus affecting shoot germination. Ten days after planting, apply Huagenwang + Shoushanghao phosphorus ester synthetic enzyme, which can promote root formation and root tip elongation, and both water absorption and nutrient absorption can be balanced. (10) Within two days after spraying, do not use irrigation-style watering; instead water by spraying, and keep the medium as dry as possible so that healing speeds up. [Editor's note] In the past two years, large-scale orchid farms and courtyard orchid rooms in the factory music ball work delta have generally reported relatively severe outbreaks of root rot, with quite serious losses, especially in some older orchid farms where the situation is even worse. Therefore, the above related control materials have been specially selected for orchid friends' reference.