Common Diseases of Herbaceous Flowers and Their Control Methods

What are the common diseases of herbaceous flowers and how are they controlled? Herbaceous flowers are those whose stems are herbaceous. Diseases of herbaceous flowers are caused by fungi, bacteria, viruses, nematodes and so on; diseases caused by parasites living on the plant body are infectious diseases, with fungal diseases being the most common. Their pathogens are all living organisms, and they can reproduce and spread, spreading and expanding rapidly under suitable conditions and causing disaster.

The following are the common types in herbaceous flowers:

(1) Damping-off

When the pathogen infects the base of the tender stem of sown seedlings, the seedlings quickly topple over at ground level. This is commonly seen at the seedling stage of scarlet sage, cineraria, China aster, cockscomb, carnation and so on. The pathogen is mostly in the surface layer of the soil; when the soil temperature reaches above 20°C and the humidity reaches saturation, the pathogen begins to harm the plants. In open-field cultivation, the incidence rate is highest from mid-May to August; in greenhouses or hotbeds, the disease mostly occurs when the seedlings have 1-2 true leaves.

Control methods: First, the soil used for raising seedlings must be thoroughly sterilized. Before sowing, treat the seeds of susceptible herbaceous flowers by mixing with 0.2% of the seed weight of ceresan. After the seedlings emerge, 2-4 kg of 1% ferrous sulfate solution per sq m can be irrigated for prevention, and thinning should be done early to strengthen ventilation.

(2) Powdery mildew

The pathogen harms the leaves, tender shoots, flower stalks and other parts of the plant, even the whole plant. The affected parts are light gray at first, then a layer of white powdery or downy material grows. When they cover the leaves, the leaves curl inward and the tender shoots bend and stop growing. Sometimes it also infects unopened flower buds, ultimately causing leaf drop or plant death. The characteristics of powdery mildew occurrence are: it is most likely to occur when the temperature reaches 18-30°C, the relative air humidity is 55%-85%, and the environment is relatively stuffy and unventilated.

Control methods: Mainly improve cultivation conditions, control temperature and humidity, and pay attention to ventilation and light transmission. During cultivation, apply less nitrogen fertilizer and more phosphorus and potassium fertilizer to increase plant resistance. In the early stage of the disease, promptly remove the infected leaves and flower stalks and burn them in a centralized manner; or isolate the diseased plants. Spray with 50% thiophanate 1000-fold solution or 50% Tuzet 1000-fold solution for control, or spray with 1000-fold 5% amobam aqueous solution.

(3) Root-knot nematode disease

An important disease harming flower roots. Common herbaceous flowers harmed include snapdragon, garden balsam, scarlet sage, cockscomb, China aster, larkspur and so on. The aboveground parts of infected plants show weak growth, stunted plants, yellowing and wilting leaves, and small flowers. The underground parts show root galls of varying sizes formed on lateral roots and fibrous roots, with a slightly rough surface; when a small gall is cut open, milky-white shiny granular substances can be seen inside, which are the nematode bodies. Females lay eggs inside the parasitic plant or in the soil; the eggs can hatch into larvae in 2-3 days in warm soil, and upon encountering suitable plant roots, they invade from the root bark. Due to the stimulation of secretions, the damaged part of the plant root swells to form a gall. Nematodes are mainly found 5-23 cm below the soil surface, with the most in the soil layer of about 10 cm. The suitable temperature for nematode activity is 12-18°C.

Control methods: Strictly implement plant quarantine to prevent the disease from spreading to disease-free or lightly affected areas; select soil without root-knot nematodes for raising seedlings or crop rotation, and soil sterilization should be carried out in flower nurseries with severe incidence; chemical control can use 20% dichloropropane to treat the soil at 5-8 g per sq m, or 4% aldicarb granules at 20 g per sq m, or 3% carbofuran granules at 15 g per sq m.

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Common Diseases of Flowers and Their Key Control Points

(1) Damping-off. Damping-off, also known as seedling blight, is a fungal disease that harms seedlings, causing the stem and root tissues near the soil surface to die and the plant to fall over. For control, mainly avoid excessively wet soil, strengthen seedling-stage management, enhance seedling stress resistance, and at the same time pay attention to maintaining cleanliness and carrying out soil sterilization.

(2) Powdery mildew. Powdery mildew is a fungal disease that harms the stems and leaves of flowers, forming a grayish-white fungal layer on the surface, and it does the most harm to herbaceous flowers and Chinese roses and so on. Control measures mainly include removing overwintering sources of inoculum, strengthening fertilizer and water management, and ventilating to reduce humidity. Powdery mildew fungi are particularly sensitive to sulfur, so sulfur powder, lime-sulfur mixture and other sulfur-containing agents

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are effective agents for controlling powdery mildew.

(3) Rust. Rust is a fungal disease; the rust fungus is an obligate parasite, and the lesions appear as reddish-brown spots, often harming herbaceous flowers as well as pines and cypresses, Chinese roses and so on. Commonly used control agents include the sulfur preparation sodium rust, colloidal sulfur, and the systemic agent triadimefon.

(4) Soft rot. Soft rot, or decay disease, is a fungal disease that causes the decomposition of living cells and harms the roots or bulbous parts of perennial flowers. It can be controlled with 1 _-fold streptomycin solution.

, Flower pests

There are many kinds of flower pests, including pests that harm roots, stems and leaves, as well as pests that harm flowers and fruits. Pests not only cause economic losses, but also greatly reduce the ornamental value of flowers. To prevent or reduce the harm of pests, measures that can be taken include protecting or releasing natural enemies, creating environments unsuitable for pests, strictly carrying out quarantine and applying insecticides to control their numbers, activities and reproduction, ultimately achieving the goal of eliminating pests.

Two Diseases of Herbaceous Flowers: Symptoms and Control Measures

News from the China Landscape Network on November 11: Damping-off and seedling blight are the main diseases during the seedling-raising period of herbaceous flowers. Cockscomb, scarlet sage, marigold, flat-topped garden balsam and so on are extremely susceptible to this disease. The two have different pathogens: the main pathogen of damping-off is Pythium aphanidermatum, and the main pathogen of seedling blight is Rhizoctonia solani, but their control methods are similar. The main symptoms and control measures of the two diseases are introduced as follows:

Damping-off is the main disease at the seedling stage when herbaceous flower seeds germinate. When seedlings are affected, water-soaked lesions appear at the stem base at or below the soil surface, then the diseased part turns brown, continues to expand around the stem, the tissue necroses, and the seedling falls over. When humidity is not high, white cotton-like mycelium grows near the diseased plants. Seedling blight can affect plants from the seedling stage to transplanting; dark brown lesions appear at the stem base, gradually become sunken, and the diseased part constricts. When the diseased part expands to encircle the stem once, the plant dies standing upright, generally without falling over.

The control measures mainly include the following methods

(1) Soak the seeds in 50% carbendazim wettable powder diluted 500-fold with water for 1 hour;

(2) Spray the substrate used for raising seedlings with 95% Lüheng No. 1 3000-fold solution to sterilize;

(3) The sowing rate should not be too large; when sowing, the bottom water should be applied in an appropriate amount, neither excessive, while ensuring that no watering is needed from after sowing until the heart leaves appear; avoid the occurrence of high temperature and high humidity in the seedling-raising site; when disease is found, promptly remove the diseased seedlings and the seedlings around them;

(4) In the early stage of damping-off, spray 15% hymexazol aqueous solution 450-fold; for seedling blight, spray 20% tolclofos-methyl emulsifiable concentrate (Rizolex) 1000-fold; when damping-off and seedling blight occur at the same time, spray 72.2% Previcur aqueous solution 800-fold plus 50% thiram wettable powder 800-fold. Spray 2 to 3 kg of solution per sq m.