Control of soft rot of orchids

Orchid friends come together, the topic focuses on the exchange of orchid cultivation techniques, to explore the problems in orchid cultivation. In recent years, what people talk about most is the prevention and control of soft rot. The disease occurs rapidly, the harm is serious, the cause is unknown, treatment is difficult, once it occurs, it is difficult to cure it with drugs. If decisive measures are not taken in time, there will be a devastating disaster. People feel that soft rot is the biggest threat to orchids at present, and they have a lot of feelings about the color change of "rot". For this reason, I have made some investigations on the cause, harm, prevention and control of soft rot, not to mention any research, nor can I draw a mature conclusion.

The cause of soft rot. Some people say that it is the influence of plant materials, some people say that it is caused by watering, others say that it is brought about by resale seedlings, and the more consistent point of view is bacterial infection. According to the conclusion of senior orchid disease experts in Taiwan, the pathogen of soft rot is Fusarium, which is parasitic in the soil and attached to the Reed head and root of the orchid plant. When the orchid seedling is transplanted and ramet, the pathogen invades from the wound. As a result, it is often the case that orchids are most likely to suffer from soft rot after ramification or trauma. In terms of climatic season, the suitable temperature for Fusarium oxysporum growth is 20 ℃-30 ℃. It is usually born from April to September, especially from May to August. During this period, coupled with other factors, such as unclean plant materials, serious pollution, often a large number of bacteria; poor ventilation in the orchid room, long-term occlusion, conducive to bacterial reproduction; too much watering, wet basin soil, affecting the permeability of the orchid root; improper fertilization, too much nitrogen fertilizer, resulting in fertilizer damage; too little light, weak plants, lack of disease resistance, and so on. In this case, orchid seedlings are more likely to be infected with bacteria and are prone to soft rot. Once this disease occurs, it spreads rapidly. it is often found that there are differences in the leaves in the morning, and in the evening, the whole orchid leaves turn yellow, and there are brown spots in the head, which expand in the shape of water stains, and then the color turns black, and there is often an outflow of secretions, giving off a bad smell. If the new bud is sick, it will be pulled up as soon as it is gently raised, and the old leaf will be broken at the slightest collision. If we do not take timely and decisive measures to rescue the orchid, it will spread the whole pot of orchids a few days later and suffer from extinction. But also through watering, changing soil and other contact, the bacteria will be transmitted to other orchid seedlings, the consequences are unimaginable. After the occurrence of soft rot, it is difficult to treat with drugs. I have used topiramate, carbendazim, chlorothalonil, daconine and other drugs for medical treatment, but all of them were of no avail and could not save the dying fate of sick orchid.

For the prevention and treatment of soft rot, we must adhere to the policy of giving priority to prevention and supplemented by treatment. Prevention is positive and active. The treatment is passive and passive.

Prevention of soft rot:

First, keep the orchid room clean. Orchids in the fresh air, no pollution of the natural environment, are generally full of vitality, rarely suffer from soft rot. In a closed orchid room, soft rot is easy to occur if you don't pay attention to disinfection. Therefore, we should pay attention to improve the small environment of orchid cultivation, often open windows, pay attention to ventilation, it is best to have exhaust equipment, even in the case of the orchid room sealed, can also keep the air smooth.

Second, watering should be scientific. First of all, it is necessary to keep the water clean and do not use sewage with bacteria. At present, with the rapid development of industry and the relative lag of environmental protection, groundwater pollution in many areas is serious, and even Rain Water is polluted by dust. It is more convenient to use sterilized tap water. After storing it for a day and night, let the chlorine in the bleach disappear and then use it. Secondly, we should use water scientifically according to the situation of orchid pots, not too dry or too wet. If it is too dry, the root will dry up and affect the growth of the plant. Too wet will rot the roots, and it is easy to breed bacteria. It is necessary to master that the basin soil is dry but not dry and is in a "moisturizing" state. When watering, we should also pay attention to open the window for ventilation or turn on the electric fan to make the water in the heart of the orchid leaf evaporate in time, avoid bad heart and prevent the infection of bacteria.

Third, fertilization should not be too thick. Heavy fertilizer should hurt the roots and cause fertilizer damage, and it is better to apply thin fertilizer frequently. The application of chemical fertilizer should be mixed with water according to the prescribed proportion, and fertilizer elements should be matched according to the needs of orchid growth. The application of organic fertilizer should be fully fermented and sterilized by pesticides before it can be applied. During the period of high temperature, it is necessary to apply little or no fertilizer, but an appropriate amount of agricultural amino acids can be applied to improve the immunity of orchids.

Fourth, timely spraying prevention. Generally spray agricultural streptomycin or chloramphenicol every 10 times 20 days to kill bacteria. Spray methyl topiramate, chlorothalonil and other fungicides. Several pesticides are applied alternately to prevent germs from growing and multiplying. However, it should be noted that improper use of drugs will produce side effects, which will adversely affect bluegrass. Long-term use of the same drugs will also make bacteria resistant and lose their effect.

Treatment of soft rot:

The rescue of soft rot should be timely, and we should often pay attention to observe the subtle changes of orchids at ordinary times. once the symptoms of soft rot are found, the leaves are yellowed and then dehydrated and withered, and the Reed is black, we must take decisive measures as soon as possible. never delay.

First, cut off the diseased plant immediately and destroy it. When cutting the seedlings, you should observe carefully. If you see the Reed head turning brown, you should continue to remove it. The cut Reed head was fine at that time, but it appeared light brown after a few minutes, indicating that it has been infected with bacteria and should continue to be removed until the incision is completely white. At the beginning, I was eager to protect seedlings and had a fluke mentality. I always wanted to protect one more plant, especially some rare varieties, even more unable to do so. As a result, the bacteria continued to spread, killing one strain after another, leading to the "annihilation of the whole army." The most heartache is a rare new product of Cymbidium, sprinkled with golden beads, which was cut off because of the loss of rescue opportunity. In the future, I have accepted these painful lessons and put up with it. Start decisively, but retain some good varieties, such as the traditional famous species Wanzi, new varieties Baohe, new plum, zebra Shuangyi and so on.

Second, the surviving orchid seedlings should be rinsed with clean water, then soaked in 0.5% potassium permanganate solution or 1000 times agricultural streptomycin solution for 30 minutes, then washed with clean water, and then replanted in a pot after drying. The original plant material orchid basin has been parasitized by bacteria and can no longer be used. New plant materials and orchid pots that have been sterilized and free of germs should be replaced. When planting, the wound of the Reed head should be exposed outside the plant material, and put on germicidal powder, put it in a cool and ventilated place, and cannot be watered immediately. After three or four days, when the wound heals and no sickness is found, the plant material will be covered and transferred to normal management.

Shou Jicheng, Zhejiang

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