Characteristics of the occurrence of the main diseases of cut-flowered gerbera flowers How to prevent diseases
Gerbera jamesonii bolus, also known as Fulang, is one of the world's five largest cut flowers, is a perennial root herb of the genus Asteraceae, native to South Africa, like warm, sunny, warm in winter and cool in summer climate environment, growing well in loose, fertile, well-drained, humus-rich sandy soil, its optimal growth temperature is 20 ~ 25 °C. Gerbera is a rookie in cut flowers, there are many horticultural varieties, the flower color is white, orange, red, yellow, pink, orange yellow, etc., the full flowering period is from May to June and September to October, as long as the temperature is suitable, it can bloom in all seasons, and the flower stem is straight, and the cut flower yield is high. Gerbera is popular with flower growers and consumers because of its wide variety of flowers, straight branches, not easy to decay, long flowering period, and significant economic benefits. Gerbera has developed rapidly since its introduction to China in the mid-1980s, especially in recent years, due to the sharp increase in the amount of cut flowers in China, its planting area has expanded sharply, with the increase of cut flower production area year by year, the disease problem has become more and more serious, and the yield and quality of flowers have a great impact, suffering huge losses. Therefore, understanding and mastering the types and occurrence characteristics of gerbera diseases is of great significance to the effective prevention and control of gerbera diseases. The occurrence characteristics of the main diseases of gerbera are introduced as follows.
1 Bacterial disease of gerbera
Gerbera spotted disease is a bacterial disease caused by pseudomonascichorii. The pathogenic body is solitary, straight or slightly curved, rod-shaped, active, and has multiple flagellar; Gram-negative reaction, gas-good, respiratory metabolism, chemical energy heterotrophic bacteria. The pathogen mainly affects chicory, lettuce, peas, melon, cabbage and other cruciferous plants, tomatoes, clovers and so on can also be affected. The pathogens mainly overwinter in the soil of the diseased field and the remnants of the diseased plants, and are spread by means of rainwater, agricultural operations, and insect carrying.
2 Gerbera virus disease
2.1 Gerbera spotted wilt
After gerbera is affected, it shows symptoms such as fading, necrosis, dwarfing, and flower deformity. The disease occurred on gerbera cultivated in Italy, France, Spain and Japan, and the pathogen was tomato spotted wilt virus (tswv), the virus body was spherical, 85 nm in diameter, with lipid coating, passivation temperature was 40~46 °C, vitro survival period was less than 5 h, and dilution limit point was 10-3. The poison is transmitted by mechanical inoculation, and the insect-borne thrips transmit the virus in a long-lasting manner. The disease has a wide range of hosts and is an important pathogen for tobacco, tomatoes, potatoes and other crops.
2.2 Gerbera mosaic leaf disease
The leaves of the diseased plant fade green, the leaves are deformed, and plaques are formed, the growth is weak, the number of cut flowers is sharply reduced, and it continues to develop, and the diseased plant dies. It can infect other crops such as ordinary tobacco and heart leaf tobacco to produce mosaic diseases, and infected with westerly cilantro can cause faded green macula and mosaic disease. The pathogen is cucumber mosaic virus (CMV), the virulochondrial spherical shape, 30 nm in diameter, with three types of mitochondrials, morphologically similar, transmitted by mechanical inoculation, non-persistent transmission of aphids. The passivation temperature was 70 °C, vitro survival was 4 days, and the dilution limit point was 10-3. The disease hosts a wide range and is transmitted
The venom is mainly transmitted by sap and aphids.
2.3 Gerbera mottled disease
Faded green ring spots appear on the leaves, and some faded green spots appear as shovel-leaf-like, and individual tissue necrosis of the spots is on the verge of spotting. When the disease is severe, the leaves become smaller, wrinkled and brittle; Some varieties have broken petals, smaller flowers (deformity), less vivid flower colors, and shorter plants. The pathogen is tobacco mosaic virus (tmv), granulous straight rod, 300 nm × 18 nm, passivation temperature of 90 ~ 95 °C. The disease has a wide range of hosts, mechanical inoculation, contact between plants, contaminated soil, agricultural tools, etc. can be transmitted, and can also be transmitted by sap, soil, nematodes and seeds.
3 Gerbera fungal disease
3.1 Gerbera powdery mildew
The disease mainly harms the leaves, and the leaves appear white mold spots at the beginning of the disease, and then gradually expand into round or oblong yellow-white spots. The lesions are covered with white, and in severe cases, the whole leaf is covered with white powder, and the later powder layer is grayish white, and the leaves are scorched.
Pathogen is (oidium sp .) The mycelium is white, epiphytic, and the nutrients are aspirated deep into the host epidermal cells with a pipette. The conidia stalk is erect, unbranched, and the conidia are produced in the full-walled form of the conidia. Conidia are oblong, unicellular, colorless, strung, and mature sequentially from top to bottom. The disease is more likely to occur when the temperature is high, the relative humidity is 80% to 90%, and the ventilation in the greenhouse is poor.
3.2 Gerbera leaf spot disease
There are two main types of gerbera leaf spot disease: (1) leaf spot fungus leaf spot disease. Small spots from purple-brown to tea-brown appear initially on the leaves, gradually enlarging to round or nearly round, dark brown spots at the edges, and small black spots on the later spots. The pathogen is phyllost icta chrysanthemi, spherical conidia, buried, single cavity, orifice. Spore-producing cells are cylindrical, colorless, smooth, full-walled spore-producing; The conidia are oval, unicellular, colorless, and flattened at the base. The artificial medium grows rapidly, the aerophytic hyphae are more numerous, the conidia are formed thinner, and the wall is membranous. Pathogens overwinter in diseased leaves with hyphae and conidia. Old leaves are more severely ill than young leaves. (2) Tailspores leaf spot disease. Small purple-brown spots initially appear on the disease-susceptible leaves, gradually expanding to round or nearly circular spots, dark gray in the center, with slightly raised brown lines on the edges, purple-brown on the periphery, and dark green mold spots on both sides of the leaf front and back. The pathogen is cercospora chrysanthemi, mycelium multi-buried, often with ovary, conidia with coarse mycelium type, olive brown or brown, lighter top color, unbranched or occasionally branched, clustered on the ovary tissue, conidia whip-shaped, straight or slightly curved, colorless, with 3 to 12 septum. Spore-producing cells are multi-budding, axial extension, cylindrical, and the spore marks are obvious. The conidia are solitary, scarred at the base, with multiple diaphragms and a smooth surface. The disease mostly overwinters on the diseased remnants and diseased leaves, and generally occurs seriously in environments with insufficient wet and humid light, heavy soil and poor drainage.
3.3 Gerbera gray mold
Water-stained round or irregular lesions appear near the ground stem of the diseased plant, which later become gray-brown to brown, the diseased part is soft and rotten, and the surface is densely covered with gray mold. When the seedlings are infected, the stems and leaves near the ground are brown water-stained and decaying, and the surface produces gray mold, and the posterior small and flat sclerotium is generated.
The pathogen is botry tis cinerea, belonging to the subphylum hemidite, grape spores, conidia straight or flexed, size 960 ~ 1 200 μm × 16 ~ 22 μm, several roots, brown, smooth, with 1 to 2 branches at the apex. The ends of the branches are often significantly expanded, forming colorless or pale bottle-like spore-producing cells, and the conidia are short and oval in shape, with a size of 12 to 18 μm × 9 to 13 μm. Pathogens overwinter in the susceptible tissues as conidia and sclerotia, and are prone to disease when the humidity is high.
3.4 Gerbera mycosiasis
The disease occurs from the base of the stem, causing the stem to rot. At the beginning of the disease, the diseased area appears water-stained, soft and brown, and gradually spreads to the stem and petiole. Later, the sclerotium of black rat feces can be seen inside and outside the stem. The typical symptom of the disease is the rapid development of soft rot in the diseased area, dense white flocculents, or black rat fecal sclerotia, each sclerotia can produce 1 to 9 ascomycetes.
The disease is caused by the fungal nucleus discoidus sclerot inia sclerot iorumfuck. The ascomycete disc is produced on the sclerotium, discoid, and has a long stalk. The ascomycetes are arranged in parallel, with permanent lateral filaments between the ascomycetes. Ascomycetes are stick-shaped or oval, colorless, ascospores, elliptical, arranged in rows. The host of the pathogen is very wide, and the pathogen overwinters in the disease residue and soil with sclerotia, and produces ascospores infestation hazards the following year. Plots with anterior stubble of cruciferous crops are severely ill. The onset of the disease is severe during the rainy season. The disease spreads through contact between diseased and healthy strains and the growth of mycelium in the soil.
3.5 Gerbera root rot
The disease is one of the most important diseases of gerbera, with a wide area and a large degree of harm, and the plant is affected during the entire growth period, and the flowering stage is the most seriously affected. The pathogen infects from the base of the ground stem, and the injured part becomes soft, water-stained, and light black; The leaves of the plant suddenly wilt and turn purple-red. When the diseased plant is removed, the disease-prone part of the stem base is easily broken, and white mold spots can grow on the surface when wet.
The disease is mainly caused by Phytophthora cryptogea. Phytophthora cryptocess belongs to the pseudomonas of the Phytophthora Phytophthora family, and its vegetative body is an insulation, multinucleated mycelium, which is generally produced by hyphae expansion and asexual reproduction to produce zoosporangia. The sporangia are pear-shaped or oval, without papillae, and the sporangia are large, with an average size of 46 μm ×27 μm, and a wide range of hosts. Heterogeneous coordination, sexual reproduction produces egg reservoirs, oospores and male organs, the egg socket is spherical in shape, containing a spherical thick-walled oospore, and the male is single-celled, colorless and transparent, perimetered. Pathogenic bacteria overwinter on the remnants or in the soil, and the overwintering bacteria are the main source of initial infection of the disease. The soil suddenly alternates between wet and dry or frequently cultivates the loose soil, resulting in many wounds at the root of the plant, and pathogens invading from the wound, spreading from irrigation water or rainwater when the conditions are suitable, resulting in a large outbreak of disease. Poor drainage and continuous cropping plots are seriously affected.
3.6 Gerbera blight
The disease is similar to the symptoms of gerbera root rot, which occurs throughout the growth period of gerbera, the root system of the diseased plant is black-brown, the diseased root cortex is peeled off, the whiskers are few, and the plant is easy to uproot. When the disease progressed slowly, the leaves of the diseased plant were purple-red or black-brown, and they withered one after another. When severe disease occurs, the plant dies in a green withered manner. The disease occurs in countries such as Italy, Australia and my country. Because gerbera is basically cultivated in protected areas, the disease can occur throughout the year, and the disease occurs more severely from April to August every year. Pathogens overwinter in soil or plant disease residues, fungal soil and affected plants are the main source of infection of the disease, high temperature and humidity weather, heavy texture of the soil will promote pathogenic bacteria
Proliferation and transmission.
The disease is mainly caused by Fusarium oxysporum, which produces dense hyphae on artificial medium, loose cotton flocculent, colorless conidia, and the inner wall of the cell-producing cells sprouts vial spore-producing, producing two types of spores, small conidia ovate to oval, size 5 to 12 μm × 2.5 ~ 3 .5 μm; Large conidia are 27 to 46 μm in size ×3 to 4.5 μm in size, spindle-shaped to sickle-shaped, hook-like at the apex, with small stalks at the base, 3 to 5 diaphragms, mostly 3 diaphragms. Pachycephalus spores are usually formed in large numbers, interspersed or apical, solitary, occasionally strung, with smooth or rough walls.
In addition, the diseases of gerbera include downy mildew (caused by bremia lactucaey), white rust (caused by a.t ragopgonis), and rotifer disease (caused by tbrv).
4 Conclusion
With the increase of the planting area of potted flowers and cut flowers year by year, the production of gerbera has developed steadily, and the disease has posed a serious threat to the production of gerbera, and growers are often helpless against the occurrence of diseases. Some diseases, such as gerbera root rot is one of the main diseases in the production of gerbera, in some areas the occurrence of the situation is quite serious, in general, its incidence of 20 % ~ 30%, severe up to 80%, flower producers in the case of unclear pathogens, habitually spray some commonly used carbendazim, bacillus and other fungicides, the result is not only can not control the spread and harm of the disease well, but also cause serious waste, to the flower production of flower farmers to bring significant losses. Therefore, to understand and understand the types and occurrence characteristics of diseases, we can study relevant control measures in a targeted manner, adopt effective control techniques and means, avoid the blindness of flower producers to disease control, and reduce the losses caused by diseases to flower production.
