The Whole Story of Treating Southern Blight: A Complete Record of Disease Management

This year has been a disastrous year for our country, with heavy losses from floods in both the north and south, a deeply thought-provoking situation, and the same is true for my household. In April, the weather gradually turned warmer, and springorchidscame to an end. At this time, Shanghai was hosting the "First International Flower Festival," and my wife and I planned to go to Shanghai to do some business. Before leaving, we moved theorchidsto the balcony outside the earthen house. Under normal circumstances, the April sunlight would not be too strong, soorchidscould go without shade. Last year our residence was renovated, and the orchids originally kept on the ground floor were moved upstairs, where the sunlight hours increased considerably compared with before. During the few days after we left home, the weather was exceptionally fine, almost like early summer. Before we returned, the orchid plants had been scorched beyond recognition, covered with spots everywhere, which was truly heartbreaking. Misfortunes never come singly. By early June, when the rainy season arrived with high temperature and high humidity, the damaged orchid plants had greatly reduced disease resistance. In addition, the new water source may have been unclean, causing a few pots of orchids to develop a terrifying fungal disease that had never occurred before: southern blight. The most severely affected was a pot of butterfly-formCymbidium goeringii. When first discovered, white mycelium was around the pseudobulbs in the center of the pot. I took it out from the orchid rack and placed it separately, and sprayed it with "Carbendazim." The next morning, the whole pot was white, and the mycelium had spread to the edge of the pot, at astonishing speed. The chilling state of it was startling. So I hurriedly poured out the potting soil, and the soil was full of white thread-like fungal bands. Most of the orchid roots had rotted hollow, and all the new growths had rotted from the base. I solemnly picked up the pot and the orchid plant, washed them clean in the stream, sorted out the rotten roots and rotten growths, then let them dry slightly. First I disinfected with "Potassium Permanganate," then soaked in "Carbendazim." The newly replaced soil was also treated at high temperature, and then I planted this orchid in a new pot. About a week later, the white mycelium reappeared. I hurriedly searched all the materials at home related to fungal diseases, and in the fourth issue of 1996 of "Chinese Orchids" I found a method of using "Miehailling" to treat southern blight. I thought that now there was hope, and I was overjoyed beyond words. I immediately cleaned the orchid plant again, replaced the orchid pot and orchid soil again, sprayed "Miehailling" on the affected areas, and replanted it. Another week passed, and the white mycelium reappeared again, truly leaving me helpless. I had no choice but to spray the pseudobulbs with "Miehailling" once more, and also went to the county "Crop Hospital" to consult, buying a bag of "Triadimefon" to apply by watering. After the pain, I reflected on the pain, and only then did I truly understand how difficult southern blight is to treat, so I had to seek advice from orchid experts. First, I called Mr. Xu Dongsheng in Fujian, but two calls in a row went unanswered. Then I called the Guangdong orchid grower Mr. Chen Shaomin, whose family said he was at the factory, the factory said he was at the company, and the company said he was at the factory. After several calls in a row, I still could not reach him. Next I called Mr. Ma Xiaoshao, director of the Guangdong Shaoguan Orchid Science Research Institute, and got through on the first try. I explained the situation, and Mr. Ma recommended that I use his "Orchid Fungus and Insect Purifier," because this medicine can decompose sclerotia. I sent the money that same day, and also wrote a letter for help to Professor Liu Qingyong, editor-in-chief of "Chinese Orchids," hoping he would give guidance despite his busy schedule. Five days later, I first received the medicine sent by Mr. Ma. I combined it with "Triadimefon" for comprehensive treatment by spraying, watering, and soaking, and the disease was basically brought under control. At that time it was the college entrance examination period, and I thought Professor Liu must be very busy and might not reply, but not long afterward, I received a warm handwritten letter from Professor Liu. In the letter, he suggested I try the antifungal ointment "Daktarin" produced by Xi'an Janssen. Since Mr. Ma's "Orchid Fungus and Insect Purifier" had already shown results, I did not use "Daktarin." However, by October, another case occurred. At this time it was the season when autumn orchids send forth fragrance. A friend brought a clump of orchids with one stem bearing four flowers of a greenish color, with side sepals aligned side by side, and a large lip hanging down without curling back, saying they were autumn orchids. When I looked, the flower shape was acceptable, but the fragrance and leaf texture were exactly the same as summer cymbidium (Jiuzilan). The plants were very weak, with only one half-mature growth of four leaves and three small growths less than five centimeters, all broken roots only seven or eight centimeters long, without a single root tip. Why would a summer cymbidium bloom in autumn? I thought it might be because the growing environment was poor, and a weak flower bud left among the broken roots and withered leaves could not receive enough nutrients, causing the flowering period to be delayed. This orchid was really growing too weakly, and I was also afraid it carried pathogens, so after rinsing, I soaked it in "Potassium Permanganate" for half an hour, which I generally do not use. After drying in the shade for two days, I planted it in superior granular soil. Half a month later, white mycelium was found on the surface of the pot. Feeling that things were not good, I repotted it to inspect, and there were many white fungal hairs below the pseudobulbs. The basal leaves of the small growths had likewise rotted, and one centimeter above the broken root ends had also rotted away. I cleaned it again and soaked it in "Orchid Fungus and Insect Purifier" for two hours. After drying in the shade, I cut off half a centimeter from the broken roots, dipped them in gentian violet, applied "Daktarin" to the rotted areas of the pseudobulbs and leaves, and the next day planted it in boiled coarse river sand. One week later, white mycelium still emerged, only much less in quantity than before. I then watered with "Orchid Fungus and Insect Purifier," and the next day watered with a dissolved solution of "Daktarin." After alternating these waterings three more times over a week, this stubborn southern blight was truly subdued, and this summer cymbidium plant was preserved as seed stock, with no pathogens found to this day. Now the otherorchid plantsare growing well. However, that pot of butterfly-formCymbidium goeringiicould not withstand repeated disturbance, and its vitality was greatly damaged. In addition, the medicinal effect of "Miehailling" was too strong (I once sprayed a pot of autumn orchids that had an ant nest, and as a result the sprayed half of the plants withered and died; perhaps it was my improper use), so it was difficult for its vitality to recover. In the intense summer heat, more than ten growths of preciousorchid plantsdied one after another, which I deeply regret. Fortunately, another pot was not infected; otherwise, this original seed stock would have been lost. I specially write this article to sincerely thank Mr. Ma Xiaoshao and Professor Liu Qingyong for their assistance, and I hope we may together add glory to China's orchid industry and benefit more orchid enthusiasts. (Zhou Weiqi)