Infectious Diseases Of The Uzambar Violet: Powdery Mildew, Fusarium, Gray Rot

2024 Author: Sebastian Paterson | [email protected]. Last modified: 2023-12-16 13:47

The Uzambara violet (Saintpaulia) is one of the favorite gardeners, and therefore widespread indoor plants. Powdery mildew, fusarium and gray rot are among the most harmful mycoses to which this culture is susceptible.

Powdery mildew is a very dangerous disease that mainly affects the leaves and shoots of plants. At first, it manifests itself in the form of a whitish bloom on the leaves of Saintpaulia, later it passes to its flowers and peduncles, and then to neighboring plants (while they infect each other very quickly). Outwardly, such specimens look like they are sprinkled with flour. When you try to simply wash off the white bloom with water, an ulcerated leaf surface appears.

In the future, the gradual dying off of the leaves and the death of the entire plant begins. Several factors contribute to the development of this disease: insufficient illumination (Saintpaulias are located in the back of the room), short daylight hours (7-8 hours a day) and high air humidity (at a low temperature of 14 … 16 ° C). Mycosis is more pronounced if the soil substrate is excessively saturated with nitrogen nutrition with a lack of potassium and phosphorus nutrition. According to experienced flower growers, the excess nitrogen can be determined by the external state of young leaves at the point of growth.

With optimal development, they increase in size evenly, and with an excess of nitrogen supply, the young leaves become denser and deformed. Although later the leaves are freed from tightness, with further growth of the plant itself, they, excessively increasing in size, become tough and brittle.

In addition, Saintpaulias overfed with nitrogen bloom weaker, and their flowers become smaller. To reduce the dominance of nitrogen over phosphorus and potassium, flower growers are trying to reduce its content in the soil coma by spilling the soil with warm (30 ° C) water (0.3-0.5 liters per pot), and then feeding the Saintpaulia with a solution of potassium and phosphorus fertilizers (1 g per 1 liter of water).

Sources of infection are usually: infected dirty equipment, pots, a diseased plant and even a single leaf cut taken from such a bush. From fungicides, such preparations are selected, the solutions of which, after spraying, would not only be effective, but would also not cause damage to the delicate pubescent leaves of Saintpaulia.

Experts recommend using a 0.2% solution of Topaz against powdery mildew, a single use of which can eliminate the disease. All plants in the collection are treated with it, including both diseased specimens and healthy ones - for prevention. Florists, who have been cultivating and breeding Saintpaulias for many years, advise against powdery mildew to use a slightly warm aqueous solution of disubstituted sodium phosphate (Na ₂ HPO ₄), which is convenient at the same time as a phosphorus fertilizer. However, they note that, although the leaves are not damaged after such spraying, burns may appear on the blossoming flowers (buds and half-opened flowers are often not affected). They recommend preparing the concentration of the solution strictly according to the instructions: for processing the leaves, take 1 g per 1.5 L of water, and for spilling the soil - 1 g per 1 L (while it is allowed to carry out no more than two sprays). In order to avoid sunburn of the leaves, the treated plants are placed in a shaded place for a day or two.

Since collectors are constantly replenishing their collections with new species and varieties of Saintpaulias, one should not exclude the possibility of bringing the infectious principle of powdery mildew into the collection. Before planting, the purchased cuttings must be treated with the Topaz fungicide to exclude the possibility of preservation and reproduction of the spores of this mycosis on them.

With high substrate moisture and non-sterile soil, plant rosettes may be damaged by soil fungi from the genera Fusarium (Fusarium) and Botritis (gray rot), which are parasites of many cultivated and wild plants; they are often present on non-rotten plant debris. With the defeat of Fusarium, the lower part of the leaves darkens and licks, a grayish bloom appears. Healthy leaves become infected from a diseased leaf.

The mycelium of the fungus Botritis begins to appear in the outlet area, rising higher as it develops: flowers and buds become covered with gray mold, while the affected areas die off. The causative agents of these mycoses develop especially intensively at low air temperatures (below 16 ° C), with abundant watering, overfeeding with nitrogen nutrition and low circulation of the ambient air. In order to prevent damage to plants by the pathogens of these mycoses, flower growers very carefully prepare the soil (sterilizing it) for planting Saintpaulia. They also strictly adhere to the regimes of watering the plant (not with cold water), regulate the temperature and humidity in the room. Experienced flower growers struggle with these mycoses using the already mentioned 0.1% Na ₂ HPO ₄ solution.

To avoid the appearance of infectious diseases of the uzambara violet, several preventive rules should be followed. Experts do not recommend placing the newly acquired Saintpaulia immediately into the collection; it is worth placing it for 3-4 weeks away from others (quarantine) in order to observe the state of the plant. If signs of disease do not appear on it, and you do not find pests that often serve as carriers of their pathogens, the violet is determined for a permanent place in the collection. When a diseased plant is found, it is immediately isolated from the rest at a sufficient distance, after which it is decided whether to destroy it or apply known methods and means of treatment. It is worth recalling that with bouquets of field and other indoor flowers, you can bring into the room both pests common with saintpaulias and pathogens.

Often, to moisten a soil coma in a pot, flower growers use a classic technique, gradually moistening it from a pallet of the same container. But when, to speed up this procedure, they put the pot in a vessel with water, filled to 1 / 2-1 / 3 of the height of the pot, then in this case, to prevent infection from entering through the water from one pot to another, the liquid needs to be changed every time.

When buying a fungicide in a retail network, you need to carefully read the instructions attached to it, check the expiration date, observe safety precautions when working with fungicide solutions. Previously, 2-3 less valuable plants should be taken for a sample in order to check the quality and effect of the drug, since different species and groups of Saintpaulias may react differently to the recommended dose of the drug. If no damage appears on young violet leaves within 8-10 days, then it can be used on other plants of the collection.

It is important for every grower to remember that pathogens are more likely to be affected by pathogens for those plants that are not properly cared for, when they do not monitor the purity of their leaves. If the leaves are dusty, they are carefully washed under a stream of warm water - 1 … 2 ° C above room temperature. You can use a kettle for this. In no case should cold water be used. After such a "shower", the flower is placed in a warm, dark place (you can in the bathroom) until the water droplets on the leaves dry, whitish spots appear on wet leaves in bright light. The pots are outside, especially earthenware, and the shelves on which they are located should be periodically washed with warm water.

It is necessary to arrange pots with Saintpaulias freely enough, and in such a way that their leaves do not touch each other. This method of arranging flower containers favors the normal development of the plant and its leaves, reduces the risk of spreading infectious diseases upon contact. When planting or transplanting, the soil must be sterilized (for example, steamed with boiling water). Each grower should regularly, or even better daily, inspect the plants of his collection in order to timely remove old or rotten leaves, faded flower stalks, preventing their colonization with saprophytic fungi and bacteria that weaken the general condition of the plant; determine the appearance of the first signs of disease. It is also important to remove the topsoil from time to time and add fresh soil.