IMPORTANT information on the risk of DISEASES in rice cultivation!
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The
Valencian Institute of Agrarian Investigations informs:
Piriculariosis (Magnaporthe oryzae):
The disease caused by the fungus Magnaporthe oryzae, is considered one of the most important of the culture. Biology: It affects all parts of the plant: leaves, knots, panicle neck and panicle. The inoculum remains in remains of the previous crop or other grasses that serve as hosts. The infection begins when conditions favorable to its development occur: high humidity (> 90%) and temperatures between 15 and 28ºC for more than 10 hours in a row. Dew, rain and wet wind cause spore emission and dispersion. Symptoms and damage: The first symptoms appear in the lower parts and are later observed in other parts of the plant. In leaves are seen small spots in the form of points that evolve towards lesions of elongated aspect, with the center of a grayish tone and the edge darker; Several stains can completely bind and dry the affected leaf. The plant renews the leaves and continues to vegetate. Discoloration occurs in the stems and dark brown necrosis appears in the knots. When the infection starts in a knot, the top of the plant dries. This area is usually a breaking point for the cane. In spike can cause lesions that prevent the grains from forming correctly. The most important lesion occurs in the neck of the panicle and directly affects the production. If the infection is early, the spike emerges completely white and erect since the grains are empty. Damage to stands is usually appreciated. The intensity of the damage will depend on several factors, such as the susceptibility of the variety, the state of development of the plant, climatic conditions and excess nitrogen fertilizer, as well as the provenance and health of the seed used. Control: Cultural measures. A series of cultural measures can be adopted to reduce their incidence, such as avoiding over-fertilization and using guaranteed seed. Use of resistant varieties. The great variability of the pathogen favors the appearance of different races of the same, reason why the response of a certain variety against the disease can be different according to the zone of culture. It must also be taken into account that the varietal susceptibility is different according to the organ to which it affects; Thus, a certain variety can be leaf resistant and panicle sensitive. Chemical control. Although it is necessary to take into account the risk conditions (humidity and temperature, fundamentally), it is convenient to propose a strategy based on the phenology of the crop, since the plant is more sensitive at certain times. In this respect, the critical phenological stages will be: a) Vegetative phase: from the end of the godson (afillolat) to the beginning of spike formation (ventrellat initiation). Watch for damage to the lower parts of the plant. Treat only if severe seizures occur. B) Reproductive phase: appearance of first spikes (ventrellat / first spikes). Treat if symptoms are observed. C) Phase of maturation: Milky Grain (Gravelle): to monitor the increase of damages in the plant and the appearance of symptoms in the neck of the panicle and in the panicle. Take into account the safety period of the product and adjust the dates if you have to carry out treatments.
