Wheat Helminthosporium rot

Symptoms are also known as Helminthosporium leaf spot and Helminthosporium rot. It is a worldwide disease. Every winter wheat or spring wheat area occurs. Spring wheat is popular in high-frequency spinning. It is a typical multi-stage disease during the whole wheat growth period, which occurs from seedlings to heading and fruiting period. Seedling stage caused by bud rot and seedling blight, the adult stage led to early leaf withering and ear rot, root rot, stem rot, leaf spot, black embryo, grain lean and so on. Among them, the occurrence of leaf spot in adult plants is universal and the damage is the most serious. Seeds with heavy shoots and seedlings cannot germinate or just sprout, they turn brown and rot cannot be unearthed. Lightly germinated soil but the coleoptile or other underground parts of the disease, mostly died before the winter or weak seedlings. Root rot and stem rot appear on the coleoptile, underground stem or young root of the seedling stage brown lesions, local tissue decay or necrosis, often cause brown lesions near the tiller node of the underground stem base, and brown fusiform marks on the leaf sheath near the ground. Size 3-51-3 (mm), generally not deep inside the stem section. Seedlings often yellow, a piece of light green to pale yellow in the field, sick seedlings short, sparse, leaves upright. The tips of the lower 1-2 leaves of adult plants are 1-2 cm coked. The roots are stunted and the axillary roots are few. The seeds and roots have brown spots on the surface of the roots. They can reach deep inside, the diseased parts rot, and severe secondary root tips. Or the central part also browned and rotted, died of childbirth, or part or all of the whole plant died completely in the middle or late part of the reproductive period. Leaf spot autumn or early spring disease produces many oval, light brown to brown spots on the leaf near the ground, size 1 to several mm. Post-jointing to adult disease, resulting in a typical light brown, oval to spindle lesions, size 1-30.5-1

(cm), surrounded by yellow halos, yellow spots in the middle of the lesion, which often grow Alternaria alternata or other second parasite, the outer light brown, visible on the conidia Stem and conidia, when the disease spreads quickly, the lesions fuse to form a large spot, causing partial or complete leaf dryness. In addition, some species can produce oval dark brown spots, about 1cm in length. Ear rot and black blasts were infected at the ear stage and brown lesions occurred on the husks or cobs. The lesions often caused most of the glume or cobs to turn brown and severely caused the half ears or whole ears to die. After infected with the seedlings, mycelium became dark brown, black pods appeared and seedlings grew thin.

The pathogen Bipolaris sorokiniana (Sacc. ex Sorok.) Shoem. called wheat root rotted Helminthosporium spp. Synonyms Helminthosporium sorokinianum, H. sativum, Drechslera sorokiniana. The sexual state is Cochliobolus sativus (Ito & Kurib.) Drechsler ex Dastur called the Maidenia rot. The asexual conidiophore stems are born on both sides of the leaf, mostly on the front, with 2-3 shoots or solitary, erect, straight or bent like knees, light brown or dark brown, base swell, size 2504.5-8 (μm) . Conidiophores broadly fusiform or elliptic, slightly curved, dark olive-brown, with 3-12 walls, mostly 6-10, 40-12017-28 (μm) in size, mostly 60-100 μm long, Obvious umbilical, truncated. There are sexual pseudocapsule shells, 530 μm in diameter; ascaria rods, each with ascospores 1-8 or 4-8, size 110-23030-45 (μm); ascospores are colorless to light brown, slender, There are 6-13 separated, size 160-3606-9 (μm). It rarely occurs under natural conditions. The temperature limit of mycelial growth is 4–37°C, the conidial germination temperature limit is 3–39°C, the optimum temperature is 22°C, and the pH is in the range of 2.2–12.4. The pH range for growth is 2.7–10.3. In addition to infecting wheat, this strain can also infect barley, oats, rye, icegrass, sorghum, setaria, and aphrodisiac. In addition, in 1989, Pak et al. found that the new species of Helminthosporium drechslera triticicola Pai and Zhang et Zhu in spring wheat in northeast China also said that Helminthosporium can cause root rot in wheat. The distribution of this strain is also more common in the wheat region of Shandong. Jia Tingqun et al. separated 14 batches of 2 584 pieces of diseased tissue. Helminthosporium accounted for 19%, of which Helminthosporium sphaeroides accounted for 77% of the total number of isolates of Helminthosporium and accounted for Helminthiasis. 32%. The spores were cylindrical, thin and clear, and had less sporulation compared with H. umbelii. The growth rate was slightly slower and the pathogenic sputum was slightly weaker. Can also be infected barley, corn, millet, etc. cause root rot. This meal, a parasitic or saprophytic fungus on wheat, and Bipolaris triticicola Sivanesan, called wheat from the creeping spores. Occasionally, wheat is also known as Drechslera avenacea (Curtis ex Cooks), which is known as D. graminum, D. gramines (Rabenb. et Schlecht.), Shoem., and D. bicolor (Mitra) Subram. & Jani. Two-colored mold, etc., lead to wheat leaf spot. In nature, helminth-infested bacteria are often mixed with other fungi, causing small and equal leaf spots. Symptoms are often complicated due to the combination of species or the proportion of bacteria. For example, there are snow mold, Fusarium, Alternaria, Cladosporium, and Aspergillus flavus in Guanzhong area of ​​Shaanxi Province. The first two species are parasites and the rest are second parasites. They are parasitic on other lesions caused by its pathogens, and some can only infect host tissues that are senescent or have poor viability.

Transmission routes and pathogenic conditions As the diseased body grows in the soil or on the seeds over the winter or over the summer, the conidium is invaded by the coleoptile or radicle, causing the median incidence of underground stems or secondary roots or subbasal leaf sheaths. Seed-bearing seeds are an important primary infestation source for leaf spot disease at the seedling stage. After the host's diseased body is completely decomposed and rot in the soil, the pathogenic bacteria will lose their ability to infect. After the jointing of wheat to the adult planting stage, the root rot continues to expand, while the leaf spot disease continues to expand from the bottom upwards, and the disease on the ground Residues and diseased parts of the plant continue to produce a large number of pathogenic conidia, spread by wind and rain, reinfection. The incubation period of the disease is only a few days to seven days. The bacterial biomass accumulates rapidly and reaches the critical mass of epidemic bacteria. The temperature is 18-25°C and the relative humidity is 100%. Functional leaves and wheat ears are heavily infected or endemic. In addition, cultivation measures also have a direct impact on the occurrence of the disease. On the production of spring wheat late sowing or early sowing of winter wheat is easy to disease, planted dense disease. Management in the field

Measures that can reduce the number of sick people falling into the field or promote the rapid decay of sick bodies in the soil (such as deep plowing, cultivating, fertilizing, watering, etc.) are all conducive to the reduction of pathogens in the soil, and the incidence is light, and these measures affect the growth of wheat. Good development, but also enhance the resistance to disease, thereby reducing the incidence. There are differences in disease resistance among varieties.

Prevention and treatment methods The disease is the disease of the whole growth period, and leaf spot and ear rot are the key to prevention and cure in the ear stage. Do everything possible to reduce the source of bacteria in the field, reduce the rate of accumulation of germs, and protect the functional plant leaves, can effectively prevent and treat this disease. 91) Agricultural control promotes crop rotation to reduce the amount of bacteria in the soil, turn autumn crops off, strengthen field management in summer and autumn, speed up the decomposition of diseased bodies in the soil; use disease-free seeds, timely and appropriate, improve the quality of sowing and reduce the incidence of seedling stage. (2) Promote the use of compost produced from Japanese enzyme bacteria. (3) The resistant and disease resistant varieties of winter wheat were selected as Yumai 21, Zhengzhou 8915, Xiong 88, Xinong 881, Qinmai 12 and Xiong 1376. (4) Chemical control 1 Seed treatment: Seed weight 0.2%-0.3% of 50% thiram WP, or WP WP 338 to be seeded at 0.2% seed weight, 20% triadimefon may also be used. The emulsifiable concentrate is seeded at a seed weight of 0.1% to 0.3%. Wheat seed dressing with triadimefon affects the areas or varieties with severe wheat seedlings. The combination of triadimefon and increasing production bacteria is recommended to eliminate the effect of triadimefon on the emergence of wheat. The amount of triadimefon per 100kg wheat seeds is effective according to the seed amount. Ingredients 0.02% - 0.03%, 40 - 60g increase in production of bacteria, physiologically active substances generated by metabolic bacteria, containing components similar to gibberellins and cytokinins, can relieve the inhibition of triadicaptopril gibberellin synthesis To promote seed germination. 2 Use 50% tumefax or 70% mancozeb WP to soak in seeds for 24 to 36 hours, and the efficacy is more than 80%. 3 At the beginning of the adult stage, the middle and lower leaves of wheat have a severe disease, and when it is rainy, spray 70% of wood MnZn or 50% of WP WP 500 times or 20% of triadimefon (Triacin) or 15% of 3 The oxazole alcohol (hydroxycamptosine) WP 2000 times, 25% enemy demulsification oil 2000-4000 times, can effectively control the expansion of the disease throughout the growth period.

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