Understanding the stem rot of orchids

In recent days, continuous high temperature and humidity, continue to receive calls from Orchid friends, about the disease of beloved orchids, especially the rampant stem rot, heavy losses. Often encounter this matter, I always tell them sadly: the key to stem rot prevention, once the disease treatment effect is very poor. Therefore, at the request of orchid friends, I collected information and pictures about stem rot in recent years, so that orchid friends can understand stem rot and prevent stem rot.

First, understand the stem rot

Stem rot, also known as Fusarium wilt and Fusarium wilt, is an orchid disease with high incidence and serious loss in recent years. The peak of the disease is from May to September every year, and the earliest onset can occur in February; the environment of high temperature and humidity is more conducive to the rapid development of the disease. The typical symptom of the disease is the withering and yellowing of the old grass (which is different from the soft rot, which begins to rot from the new seedling), which shows that the core leaves of the old grass start yellowing from the base, and then develop rapidly from the bottom up, from the inside out. A seedling of old grass will wither and die within 1-2 days, and if touched by hand, the whole grass will be broken from the ring of the petiole. Inexperienced Lan you often think that they are fading old grass, but by the time the disease continues to develop and more strong grass falls down, it is often incurable.

Picture 1: a diseased seedling yellowing from the core leaves from the base (the initial stage of the disease)

Picture 2: the whole withered and yellow diseased grass (in the middle of the disease)

At this time, if you pour the pot, it can be found that the root system of the diseased seedling is still intact, and even the crystal head exists, and the new buds issued in that year are also intact. But if you cut open the false corm of the diseased seedling, you will find that the inside of the corm has turned brown, even rotten. Continue to cut down can also find that those green leaves of seemingly intact seedlings, the interior of the pseudocorm has been infected and discolored, falling grass is only a matter of time. It can be seen that the spread of the disease is very hidden.

Picture 3: diseased seedlings with new buds

Photo 4: continue to cut open the adjacent pseudo-corms and find that they have been infected.

As for the pathogen of stem rot, there are many literatures about Fusarium oxysporum, Fusarium oxysporum. I temporarily agree with this judgment and do not want to make further textual research. Because I once had this idea, I took the sick seedling to the agricultural research department, but I had to pay 50,000 yuan in advance to determine what the pathogen was, which stopped the idea of getting to the bottom of it.

From the point of view of the incidence of stem rot, it is indeed like the characteristics of Fusarium oxysporum infecting plants, which is characterized by vascular bundles that infect plants and block plant water transport channels after mass reproduction, resulting in dehydration, lack of nutrition and death. All bluegrass with stem rot is withered from the base, gradually upward, the whole plant is dehydrated, until from yellow to brown, to death. I have observed that the incidence of diseased plants in direct sunlight is very fast, changing from turquoise to yellow in 2-3 hours. in fact, it is the evaporation of light that accelerates the process. Orchid friends often reflect this phenomenon, saying that it is very strange that they did not go to see it in the afternoon and withered when they came back in the evening, thus feeling scared and mysterious about stem rot. In fact, he had already got sick before the dead grass, but he just didn't notice it.

For bluegrass with stem rot, it is very difficult to cure. At most, it is discovered early and planted in order to save the seedlings of Qianlong that are not infected with germs and leave a seed. And the premise is that you must have the ability to prevent and identify stem rot.

2. Prevention of stem rot

Is there any sign of stem rot before the disease occurs? Through the practice of Lanyou, it is found that stem rot, including soft rot, has a common characteristic at the initial stage of its occurrence: stagnation of new buds. Especially in May and June, once the new buds stop growing, we should pay special attention to the changes of the whole orchid plant, especially to observe the decline of the old grass, once the disease is found, we should not be soft, pour the pot and separate the plant. In order to prevent accidental injury, you can also put the orchid basin in direct sunlight for half a day, and then look at its changes, healthy bluegrass will not lose water and become yellow because of half-day exposure.

However, it is very hard to watch new buds every day. How easy is it to observe the growth of new buds? Here I would like to introduce to you a simple method: the growth line method. That is, with a water-based white marker, draw a horizontal line at the base of the new bud. Due to the inconsistent growth rate of the leaves (the speed inside is fast), the growth traces can be clearly seen the next day, which is simple and interesting. See the following figure:

Stem rot is a soil-borne disease, and the real and thorough prevention should be done from the following aspects:

1. Prevent the orchid plant from having a wound. The wound caused by frequent ramets of orchids is the greatest harm, so we should try to deal with the wound and apply wound healing agent immediately after ramet (there are finished products on the market); to prevent infection caused by insect bites in the soil, insecticides can be applied in the soil, carbofuran is recommended.

two。 Dispose of the diseased seedlings in time and thoroughly, and the plant materials and pots used for the diseased seedlings should be discarded as far as possible.

3. Do not use the method of sitting pot to water orchids to prevent cross infection

4. Keep the orchid environment clean without stagnant water and dust

5. Adhere to drug prevention, in the peak period, every 15 days with medicine basin, recommend more than 30% of the wettable powder, through the practice of Lanyou, it has a special effect on the prevention of stem rot. I will publish orchid knowledge and pictures every day, take you in-depth understanding of orchids, teach you to easily raise orchids, you can always ask me or leave a message below if you don't understand orchids. If my knowledge brings you help, I hope you can help me or forward it to help more people!