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Wheat Powdery Mildew

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» wheat diseases, triticum sp.

Introduction

Triticum sp.

Powdery mildew is one of the most widespread diseases in cereal grains, especially wheat and barley, but can also occur gramineae in pastures and meadows.

View Plant Profile of: Triticum sp.

Symptoms

Triticum sp.

Disease begins to manifest early spring in April, May or in March, the obvious symptoms of all plant organs, especially the stems and leaves.

At first, on strains based, sheaths and inferior leaf limb appear yellow or light green spots covered with felt pillows, white, dusty, isolated or confluent, under which the host tissue necroses. These pillows are consist of mycelium and conidiophore with conidium fungus.

Sometimes at heavily attacked plants, mycelium dry and falls and in its place is observed oblong spots on the leaves, purplish brown dead tissue.

When weather conditions are favorable, the disease spreads and upper leaves, and even wheatears. In mycelian felt that becomes reddish yellow with time, appear numerous blackish brown dots, visible with the naked eye, which are perithecium fungus. They resists on diseased leaves or stems until autumn or next spring.

Diseased plants are hampered growing, wheatears are small, shriveled grains, because the leaves strong attack are early dry.

Attacked plants suffer and changes in physiological processes: pronounced decrease in the quantity of chlorophyll in the leaves covered by fungus mycelium, increased perspiration and respiration intensity decrease for very strong or very weak attacks, the intensity of respiration is increased in the case of a medium attack. When the attack is intense during twinning and formation of straw, there was a significant reduction of the crop.

Erysiphe graminis fungus can cause infections and autumn (the winter wheat and in this case), diseased plants are sensitive to frost.

Pathogen

Triticum sp.

Powdery mildew is produced by Erysiphe graminis f. sp. tritici March, family Erysiphaceae, order Perisporiales, class Ascomycetes.

Fungus mycelium consists of hyphae branched, multicellular, it is ectoparasites and fixed on the surface of organs attacked by apressor. By extending their, appear voluminous haustorium, digitally branched, which penetrate the epidermal cells of the host plant. On mycelium is formed conidiophores with conidium. Conidiophores are short, hyaline, simple, willing perpendicular to spawn, with almost spherical basal cell. Conidium are unicellular, ellipsoid, slightly truncated at the ends, hyaline, 18-36x11-17 μ, slim membrane and arranged in short chains. They germinate at a minimum temperature of 3°C, with the optimum between 11-17°C and light conditions. Conidium retain their viability relatively quickly. To the end of the growing fungus forms perithecium (sporifer body) slightly flattened globular core of 115-236 μ in diameter, with blackish brown and pseudo-parenchymal peridium provided on the outside with appendix short, simple, brown. perithecium has ascus ovoid, oblong, with basal pedicel, hyaline, with double membranein which are differentiated 8 unicellular, ellipsoidal and hyaline ascospores.

Life Cycle

Triticum sp.

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Prevention and Control

Triticum sp.

Preventing and combating pathogen is recommended to follow a set of measures agrophytotechnical: sowing the optimum time and distance determined by culture technologies, deep plowing, crop rotation, application of fertilizers in balanced doses, drain excess moisture from the soil, destruction of remnants diseased plant, stubble burning, cultivation of resistant or tolerant varieties.

Even environmental conditions and applied agrotechnics influence plant resistance to powdery mildew: eg. after a strong phosphorous nutrition plants become more sensitive while potassium increases their resistance. Urea-based herbicides increase the intensity of powdery mildew attack while those based on growth stimulators it's not influence, seem to decrease it.

 

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