Flower Disease Identification and Control Methods, and Mushroom Disease Identification Techniques

I. Physiological Diseases

The main causes of physiological diseases are: unsuitable temperature, unsuitable light, water imbalance, unsuitable nutritional conditions, excessive soil salinity, harm from toxic gases and substances, unsuitable soil pH, and so on, all of which can affect the normal growth and development of flowers and lead to disease. Therefore, this type of disease is also called non-infectious disease. It cannot be effectively controlled by spraying chemicals. It occurs relatively commonly in the field, has no disease center, and the time and site of onset are relatively consistent; it is not contagious. Physiological diseases share a common feature: they often first appear on young leaves and new shoots, such as leaf yellowing, withering, and falling, root rot, and the appearance of soft, slender, easily broken stems and leaves, lodging, and other symptoms of poor growth.

II. Bacterial Diseases

Flower diseases caused by bacteria. If not controlled in time, they often cause devastating disasters. Bacterial diseases mainly include types such as streak, spot, blotch, wilt, and rot. Bacterial leaf spot generally appears as acute necrotic spots, water-soaked in appearance, with a yellow halo around the lesion, such as bacterial leaf spot of chrysanthemum and begonia. Bacterial rot has a fishy odor, and the rotting tissue carries yellow bacterial ooze, such as soft rot of lily, and rot and soft rot of calla lily. Bacterial wilt often causes green wilt (whereas fungal wilt is often accompanied by yellowing), such as green wilt of chrysanthemum and dahlia, bacterial wilt of carnation, bacterial wilt of chrysanthemum, and bacterial wilt of primrose.

III. Fungal Diseases

The vast majority of flower diseases are caused by fungi. For example, downy mildew of chrysanthemum, gray mold of geranium, anthracnose of rubber tree, anthracnose of osmanthus, black spot of calla lily, downy mildew of rose, brown spot of cockscomb, tulip blight, and damping-off and seedling blight of various flower seedlings. The mycelium of fungi is the vegetative body, and asexual and sexual spores are the reproductive bodies. They spread by wind, rain, insects, or seeds and seedlings and weeds, and can also be transmitted from generation to generation through soil. They invade the plant body through natural openings such as stomata, hydathodes, and lenticels on the epidermis of flower plants, as well as through various wounds. Fungal diseases often cause symptoms such as rot, wilt, and discoloration in plants. The signs are especially obvious, and the pathogen or its modified forms can be observed with the naked eye, such as white powder, gray mold, black mold, downy mildew, black spots, and sclerotia. Fungal necrosis is one of the most important symptoms of fungal diseases.

IV. Viral Diseases

Mainly caused by viruses. Viral diseases of flowers are mostly chronic diseases affecting the whole plant. The external symptoms are often fading of flower or leaf margins, ring spots, blistering, yellowing, necrotic spots, clustered spots, or leaf narrowing, shrinkage, and deformity of branches, leaves, flowers, and fruits. Viral diseases have only symptoms, not signs, which differs from fungal and bacterial diseases. The symptoms of some viral diseases are easily confused with non-infectious diseases. The difference is that the occurrence of viral diseases clearly spreads gradually from point to area, and the symptoms appearing on diseased plants often begin at the top and then spread to other parts of the plant. For example, viral disease of Asteraceae flowers, viral disease of golden-edged Daphne, and viral disease of carnation. Viral diseases are mainly transmitted by pests with piercing-sucking mouthparts, such as aphids, leafhoppers, planthoppers, psyllids, and thrips, and can also be transmitted by nematodes and fungi in the soil, as well as by seeds, seedlings, and pollen. At the same time, during grafting and management of flower seedlings, contact between diseased plants and healthy plants, and asexual propagation materials such as cuttings, tubers, corms, and bulbs can all be opportunities for the spread of viral diseases. Even when pruning branches or cutting flowers, people's hands and tools are conditions for transmission.

V. Nematode Diseases

Root-knot nematode disease can harm many kinds of flowers, such as root-knot nematode disease of various ornamental tomatoes and ornamental peppers, and root-knot nematode disease of cockscomb and Asteraceae flowers. This disease only infects the root system of the plant, with lateral roots being more severely damaged. Many root knots form on the lateral roots and connect with each other into a rosary-like shape. The root knots are often spherical or conical, vary in size, and have many fibrous roots on the surface, forming clustered fibrous roots. When a root knot is cut open, many translucent white, needle-tip-sized, pear-shaped nematodes can be seen. In the early stage, the root knots are light in color, smooth on the surface, and relatively firm, gradually becoming light brown, brown, and dark brown and rotting. The nematodes feed on sap inside the galls. Infected plants show malnutrition, dwarfing, small and wrinkled leaves, and clustering, then gradually wither, with root necrosis, resulting in consequences such as leaf blight and flower drop.

VI. Control Measures

To control flower diseases, the following key measures should mainly be carried out:

1. Strictly implement relevant national quarantine regulations. Diseases subject to quarantine must be strictly guarded against. Seeds and seedlings must not be introduced from areas where such diseases occur or from abroad; when purchasing seeds and seedlings, they should be carefully inspected. If quarantine objects are found, they should be resolutely refused and not accepted, and destroyed by disposal such as burning or deep burial.

2. Select disease-resistant varieties. For example, even for the same Asteraceae flower varieties, small-scale introduction trials should be conducted, and some should undergo inoculation identification and natural induction identification to screen out varieties with strong disease resistance.

3. Strengthen the disinfection treatment of soil and seedlings. Especially for many precious flowers, whether planted locally or as potted plants, the soil must be disinfected, such as by spraying potassium permanganate and mixing in quicklime powder. Where conditions permit, carbendazim and quintozene should also be used for disinfection and sterilization. The former is mixed at 1.5 grams per square meter, or can be prepared into medicinal soil at a ratio of 1:20 and spread on the seedbed; the latter uses 4 grams of quintozene and 5 grams of zineb per square meter of nursery land, mixed and then evenly mixed with 12 kg of fine soil. When sowing, placing it underneath and covering on top has a special effect on anthracnose, damping-off, seedling blight, and sclerotinia. When sowing seedlings, seeds can be soaked in a 0.3% to 0.5% potassium permanganate solution for 0.5 to 2 hours, rinsed, drained, and then sown.

4. Strengthen cultivation management.

First, greenhouse flowers should be given attention for ventilation and light transmission. Even in severe cold winter, the side film should be uncovered or windows opened every day at noon to reduce humidity inside the greenhouse; otherwise, it will induce major outbreaks of gray mold, leaf spot, downy mildew, and powdery mildew. Light intensity should be controlled at a level suitable for plant growth and development.

Second, rational irrigation, drip irrigation, furrow irrigation, or watering the soil surface should be used to prevent splashing of irrigation water from carrying pathogen spores or bacteria onto healthy plants, which can effectively control disease occurrence. Water should not be allowed to remain on petals or leaf surfaces, providing conditions for pathogens to germinate and invade plants. Too high soil moisture will cause harm to roots from various root rot pathogens.

Third, during transplanting, pruning, and pinching, wounds should be avoided as much as possible, since they provide entry points for pathogens. It is best to operate on sunny days to facilitate wound healing and prevent pathogen invasion. When taking cuttings, disinfection should be carried out, and transmission of pathogens through fingers and tools should be avoided as much as possible.

Fourth, rational fertilization. Do not apply nitrogen fertilizer in a one-sided way; appropriately increase the application of phosphorus and potassium fertilizers. Excessive fertilizer application can instead cause fertilizer damage to plants and even cause yellowing and poor growth.

Fifth, pay attention to field hygiene. Removing diseased plants, diseased leaves, and weeds and carrying them away from the cultivation site for destruction can reduce or even completely eliminate the density of pathogens in the site and lessen disease occurrence. This is especially effective for controlling bacterial diseases, viral diseases, or systemic diseases such as wilt.

5. Carry out chemical control at the appropriate time and to an appropriate degree. According to the type and severity of the disease, protective agents, eradicant agents, therapeutic agents, and so on can be used.

For fungal diseases, generally the following can be selected for control: Bijunsha, Penkejun, 72.5% Previcur SL, 15% triadimefon wettable powder, 50% procymidone powder, 64% oxadixyl mancozeb wettable powder, 50% carbendazim wettable powder, and so on.

For bacterial diseases, generally the following can be selected for control: 72% agricultural streptomycin wettable powder, 77% Kocide wettable powder, 25% copper ammonia complex aqueous solution, and so on.

For viral diseases, generally the following agents can be used for control: 1.5% zhibingling emulsion, 20% virus A wettable powder, 83 resistance inducer, and so on.

To control root-knot nematode disease, kexianling emulsion can be selected, or after onset, 80% dichlorvos 1000-fold solution can be used to drench the rhizosphere soil of flowers to kill nematodes.

Physiological diseases are not contagious. By improving the environmental conditions that cause the disease and implementing symptomatic treatment, plants generally recover relatively easily.