How to prevent and control soft rot in orchids? Starting from the characteristics of the pathogenic bacteria

OrchidsCultivation: Discussing from the characteristics of the pathogenic bacteriaSoft rotdisease prevention and control

Recently I consulted some materials related to soft rot, and some excerpts are as follows:

Orchid plantsSoft rot among plant diseases is an infectious bacterial disease, and its pathogenic bacteria belong to the genus Erwinia.

The characteristics of plant pathogenic bacteria are:

1. Bacteria are a type of prokaryotic single-celled organism with a simple structure; a few are autotrophs, while most are heterotrophs. Among heterotrophic bacteria, most live a saprophytic life, and a few live a parasitic life.

2. Bacteria reproduce by binary fission and reproduce very quickly. Under suitable conditions, they can reproduce one generation every 20 minutes, and one cell can multiply to hundreds of millions after a day and night.

3. Bacteria do not contain chlorophyll and cannot make their own nutrients; they rely on parasitism and saprophytism to survive, and are heterotrophs. All plant pathogenic bacteria are non-obligate parasites. Pathogenic bacteria with strong parasitic ability infect the green parts of plants, while pathogenic bacteria with strong saprophytic ability infect the storage organs of plants or parts with weaker resistance.

4. Most pathogenic bacteria are aerobic, and a few are facultatively anaerobic. Pathogenic bacteria can tolerate low temperatures, and the most suitable temperature for growth is around 26---30 degrees. Except for a few that prefer high temperatures, they generally stop growing at 33----40 degrees.

5. Pathogenic bacteria mainly enter host plants through two routes: one is through natural openings, and the other is through wounds.

6. When a bacterial disease occurs, some changes in physiological activity that cannot be observed externally first occur in the affected parts, producing physiological lesions. Subsequently, cells and tissues also undergo lesions, and finally it develops into lesions that can be observed externally.

7. Bacteria of the genus Erwinia have single cells and are short rod-shaped, aerobic or facultatively anaerobic. Some have nutritional requirements requiring special growth substances; when organic nitrogen compounds are supplied, they generally grow better. The types of Erwinia bacteria that parasitize plants cause dissociation of plant tissues, manifesting as soft rot symptoms.

After understanding some characteristics of the pathogenic bacteria of orchid soft rot, targeting these characteristics and combining them with years of personal practice, prevention and control of orchid soft rot should be done from four aspects.

1. Environmental aspects. The environment is the foundation for preventing and controlling orchid soft rot.

1. Cleanliness and hygiene

Starting from the orchid-growing environment, pots, potting media, tools, and so on, do a comprehensive job of cleaning and hygiene to reduce the breeding of harmful bacteria.

2. Alternate dryness and moisture

The orchid-growing environment, pots, and potting media must not remain constantly wet and moist. Especially under high temperature and high humidity, they must remain dry for a certain period of time.

3. Regular disinfection

After the orchid-growing environment dries, promptly carry out disinfection, sterilization, and pest killing, and the effect is better.

2. Management aspects. Management is the means of preventing and controlling orchid soft rot.

1. Strengthen ventilation

The genus Erwinia is facultatively anaerobic. Ventilation can increase the oxygen supply, and oxygen has the effect of killing or inhibiting the growth of Erwinia. During ventilation, fresh air must be continuously replenished for a better effect.

2. Moderate water control

Under high temperature and high humidity, orchid pots must not remain constantly wet and moist. Water should be controlled moderately, with drier management, so that the potting media becomes loose and fresh air can enter the potting media and take effect.

3. Moderate light

Shade during high temperatures, but do not shade too tightly; there should be scattered light. If conditions permit, direct sunlight before 8 a.m. should be fully utilized, as it both sterilizes and strengthens the plants.

4. Use less chemical fertilizer

Some Erwinia species have nutritional requirements requiring special growth substances, namely organic nitrogen compounds. Based on this characteristic, use less or no chemical fertilizer containing organic nitrogen compounds, cutting off the source of the nutritional requirements of Erwinia.

5. Reduce disturbance

Do not love and pamper them too much; reduce human disturbance and harm to orchids, and prevent wounds from appearing.

3. Orchid plant aspects. The orchid plant is the key to preventing and controlling orchid soft rot.

1. Do a good job at the introduction stage

Introduced tissue-culture seedlings and greenhouse plants are prone to soft rot, mostly not because they themselves carry bacteria, but because they lack or do not have the ability to regulate and adapt, and their resistance is not strong. When introducing plants, pay equal attention to looking at the orchids and looking at the environment, and try to choose orchids from similar or even poorer environmental conditions. Do not introduce plants during periods of high temperature and high humidity. The best time for introduction is autumn, so that the orchids have a longer adaptation period.

2. Grow strong orchids

Truly strong orchids have strong regulating and adapting abilities and good resistance, and these cannot be grown by relying on greenhouses and fertilizers. Growing truly strong orchids requires sufficient light, fluctuating temperature differences, frequent tempering, and enough time.

3. Control excessive growth

During high temperature and high humidity, orchids also grow fastest. Once orchids grow quickly, their resistance weakens, and harmful bacteria can easily invade. Controlling excessive orchid growth is also key to preventing orchid diseases.

4. Treatment aspects. Treatment is a passive measure for preventing and controlling orchid soft rot.

1. Soft rot cannot be cured

From item 6 of the characteristics of plant pathogenic bacteria, it can be known that by the time symptoms can be seen with the naked eye, the invaded orchid is already in the late stage, and no medicine is of use.

2. Observe frequently and detect early

Although soft rot cannot be cured, it is still necessary to observe frequently. For key orchids, orchid pots, and orchids with abnormalities, be especially careful. Only by detecting early can treatment be early, with fewer infections and smaller losses.

3. Treatment methods

Once soft rot is found, it must be treated promptly. The conventional and currently most effective method is division of plants. First take the plant out of the pot, start cutting from the farthest growth, separating growth by growth, until reaching the growth where the cut surface changes color. If there are only one or two growths, do not take the plant out of the pot; first use medicine, then stop watering, let it dry thoroughly, and water again when the orchid shows signs of dehydration, and try your luck.