Exploring Soft Rot in Chinese Cymbidiums and Tips on Pest and Disease Control

If there are two diseases that trouble cymbidium growers the most, they would have to be mosaic virus andsoft rot. The former is a viral disease with no cure once contracted; and although the latter is not untreatable, why does it still cause us so much distress? 1. Where does the disease come from? When treating human illnesses, the key is to prescribe the right medicine so the disease is cured at once.Orchidsare no different. Let us first look at the source ofsoft rot: Chinese cymbidiumsoft rot(Bacterial soft rot) is a bacterial disease, and its pathogen is: Erwivia carotovora. This conclusion is very important -- it confirms that the pathogen is a bacterium, not a fungus or anything else. There are 5 bacterial diseases that harmorchids, of which 4 harm Cymbidium plants, and 3 harm the vegetative organs of Cymbidium plants, namely: bacterial brown rot, Chinese cymbidium soft rot, and bacterial brown spot. Among these 3 diseases, only Chinese cymbidium soft rot is mentioned in books as being able to harm the plant's pseudobulbs, and its pathogen -- Erwinia -- can indeed cause soft rot in some plants. 2. What are the medicines? Orchidsare too precious. When disease appears, we apply medicine to treat it; even without disease, we apply medicine from time to time to prevent it. When leaf tips turn black, we use thiophanate-methyl and carbendazim; when a plant develops soft rot, we still just spray these medicines and leave it at that, but then we see the disease will not stop, so we conclude: orchid soft rot -- an incurable disease! Soft rot is a bacterial disease, and it has its own specific treatment medicines, namely: bactericides (alkaline CuSO4 -- a broad-spectrum bacterial disease medicine, usable as a spray) and antibiotics (agricultural streptomycin). Of course, if one can find medicines specifically targeting Erwinia, the treatment would be more targeted and the effect better. And some of the medicines we commonly use do not necessarily work on bacteria -- just as there is no medicine that cures all human diseases. When applying medicine, pay attention to choosing the right timing; when applying, the solution must directly contact the affected area; if the solution has low adhesion, this can be improved by increasing its concentration; at the same time, improve the disease environment to assist treatment. 3. Adverse consequences of medication (1) Causing the death of a large number of non-plant-pathogenic bacteria. Just as during human chemotherapy, the drug kills not only cancer cells but also normal cells, making the person very weak after chemotherapy; when we catch a cold or fever, we hastily take antibiotics, and by sheer luck the illness may improve, but the drug disrupts the balance of gut flora, and after recovery we often become constipated. The same principle applies to plants. Chemical medicines are highly targeted things that can solve the key problem at once, but they also destroy the overall balance, triggering a series of subsequent changes and adjustments until a new balance is reached again. (2) Pollution. For example, copper-containing compounds have adverse effects on humans, plants, and animals alike. Our original intention in growingflowersis to live better -- whether for commercial production or home enjoyment, harming health is always a bad thing. (3) Triggering changes in pathogen resistance. As just mentioned, destroying one balance will trigger the establishment of a new balance, and of course the pathogens themselves, in order to survive, will also throw themselves into this "construction." Many people may have personal experience of this -- it is the adverse consequence of antibiotic abuse. (4) Even with the right medicine, the disease may not be eliminated. Because the solution may not effectively contact the pathogen, such as bacteria inside plant tissues. I recall that a while ago on a Chinese cymbidium forum, a grower asked why, after soft rot appeared, applying medicine and immediately dividing and isolating theplantsfor cultivation still showed no effect, and in the end all were lost; whereas without dividing, sometimes one or two plants might survive. This may be because dividing after disease increases the chance of wound infection, and bacterial diseases are harder to control than fungal diseases. With reinfection, spraying medicine only on the plant surface may yield very little effect. 4. Returning to the starting point of everything, thinking again Prevention is better than cure -- integrated control is the key! As mentioned above, when a balance is destroyed, we try every means to repair it. So why don't we think about how to establish a more stable balance, so that it is not so easily disrupted: (1) Strengthening the plant's own constitution. Whether at the point of purchase or in later care, strong seedlings always have stronger disease resistance. (2) Selection of soil and substrate. A plant is rooted in its roots, and soil and substrate are where the root system lives. Speaking of this, we must again bring up what was just said: if a balance network is woven from multiple strands, it is inevitably harder to break. The composition and physical-chemical properties of the soil substrate determine what kind of physiological and biochemical reactions can occur within it, what kind of fungi can inhabit it, and ultimately determine the type and growth direction of the plants above it. Natural soil may seem nutrient-poor and poor in physical-chemical properties, but as a whole, it has already coordinated all elements almost perfectly -- of course, this is speaking from a broad perspective. Homeorchid growingneed not all use natural soil, and doing so is also not conducive to sustainable development. And although artificial humus soil does not have the same composition as natural soil, its diversity of nutrients and its buffering capacity against the external environment are also stronger than single-component substrates. Of course, single-component substrates are easier for us to regulate, and plant growth may be faster, but do not forget that as one thing waxes, another wanes. Moreover, if following a normal curve, the peak position is inevitably also where instability lies -- and this peak can be applied to plant growth rate. In summary, it is hard to say which substrate is best; different purposes have their own strengths, and one should apply them flexibly. (3) Environmental factors must be regulated. For a plant to develop disease, there must be a pathogen, and there must also be environmental conditions that favor the pathogen. Generally, cold and humid environments help disease develop, so we need to promptly take various measures to nip problems in the bud. (4) Rational use of chemical medicines. Everything has its limit, and so do medicines. They are not unusable, nor should they be used frequently. If spraying is needed, attention should be paid to reducing the chance of skin contact. And the types of sprays should also be used in coordination with one another, to prevent a single type from causing changes in pathogen resistance. This point also reflects the principle of "balance" just mentioned. Summary: When encountering problems, we cannot merely resolve the immediate conflict. Through deeper understanding, we can often uncover where deeper problems lie, and by drawing inferences, fully apply one principle to various aspects and levels -- because many things are ultimately one, whether problems or solutions. (Author: Plum Blossom King) (References: "The Complete Book of Chinese Orchids" by Chen Xinqi and Ji Zhanhe, "Plant Pathogenic Bacteriology" by Wang Jinsheng, and special thanks to my plant pathology teacher for the inspiration!)