According to the Plant Protection Department, currently in the southern provinces and cities (from Binh Phuoc to Ca Mau) there are about 600,000 hectares (summer-autumn 200,000 ha, autumn-winter-season rice 400,000 ha) from the period plated to the bar – rose.
According to the National Center for Hydro-Meteorological Forecasting, the weather in the southern provinces in the coming time will have heavy rain, thunderstorms and intermittent sunshine, which is a favorable condition for many organisms harmful to rice. outbreaks, especially leaf blast; cotton-neck blast; even blight (in conditions of heavy rain combined with strong winds).
Currently, according to the report of the Sub-Department of Cultivation and Plant Protection of the southern provinces, summer-autumn rice is in the stage of flowering – blooming with 200,000 hectares. In the coming time, if there are prolonged storms, cotton-neck blast will cause damage on summer-autumn rice and leaf blast disease will thrive on autumn-winter-seasonal rice tea.
In order to protect the remaining summer-autumn acreage and safe autumn-winter-season rice in 2021, the Plant Protection Department suggested that the southern provinces and cities need to strengthen the investigation, detection, and zoning of rice infected with pests and diseases in stages. growing to direct and guide farmers to prevent and control, especially with leaf blast and cotton-neck blast disease on the remaining areas of summer-autumn rice, autumn-winter rice – summer rice is in the tillering stage. – rose.
In addition to leaf blast and cotton neck blast, localities still have to strengthen inspection and guide farmers to prevent other rice pests and diseases where there is a high density and rate to protect production in epidemic conditions. Covid-19 is causing a lot of difficulties for society in general and for plant protection work in particular.
Notes on blast disease
Blast disease fungal Pyricularia grisea Sacc., formerly known as Pyricularia oryzae Cav. pests and is reported to be present in more than 80 rice-growing countries around the world.
Many studies show that the disease is increasingly giving rise to many new strains with high toxicity, so it is difficult to treat. According to Dr. Nguyen Thi Phong Lan and her team, in the Mekong Delta, there are over 40 strains of the fungus Pyricularia grisea that cause rice blast disease.
Symptoms and effects:
The fungus can attack on leaves, stems, cotton necks, sprouts or rice seeds.
– On leaves: Initially, the disease is very small, but in the middle of the disease, the leaf cells are necrotic and dry, gray, then the disease becomes larger and has a diamond shape. When the disease is severe, many diseases link together causing the whole leaf to “burn”.
– On leaf collar: The disease attacks right at the leaf collar between the leaf blade and sheath, the disease turns red-brown after turning to dark brown, severe disease causes leaf breakage and leaf damage.
– On the stem: The brown spot causes atrophy, if the disease occurs when the rice is flowering, the whole flower will be white, but it is more difficult to pull it out by hand than the white flat symptom caused by the stem borer.
– On the cotton neck, the cotton neck: The disease attacks right at the cotton neck or the stem neck, the brown color rots and causes the whole cotton or each spike to be flattened. If the disease appears early, the whole cotton or each ear of rice will be white.
Conditions of development
– Blast disease thrives in overcast weather conditions, with few hours of sunshine in the day, with fog or drizzle in the early morning, the most suitable temperature in the range of 18 – 26 degrees Celsius. The disease causes the most damage in the winter-spring crop, but if in the summer-autumn and autumn-winter crops, when the weather conditions are favorable for fungal growth, such as prolonged storms, the disease will still cause severe damage.
– Factors such as infected variety (Jasmine 85, Nang Hoa 9, VD 20, RTV, OM 4900, OM 5451…), thick seeding, excessive nitrogen fertilization, horizontal rice leaves, wide leaf blades, water shortage in the field, grass Many wild species are favorable conditions for fungi to arise, grow and cause serious diseases.
The development cycle of blast disease from the time the spores first penetrated to the time of spreading and spreading strongly.
– For rice blast disease spores, if conditions are favorable, 24 hours after contact with rice plants, the spores will germinate and begin to penetrate inside plant tissues.
– About 48 hours after the disease, the needle spots appear. From 5-7 days after penetration, the fungus has produced new spores and continues to spread. Each swallow’s eye disease releases 2,000 – 6,000 spores/day and spreads very quickly, the field can be completely damaged.
– Spores produced on the upper leaves can infect the rice germ, rice seed at the flowering stage. Therefore, the prevention and treatment of leaf blast disease is not good, the rice field is very susceptible to infection with rice blast disease.
– Conditions for spores to release are by water or dew drops, and the means for spores to spread far is by wind. However, if there is a lot of water and it rains heavily, the spores are slow to release and spread less
To protect the summer-autumn rice at the bud-blooming stage: It is necessary to spray insecticides when the rice is barely blooming and when the rice is blooming.
Autumn-Winter Rice – Season:
– Thoroughly tilling the soil, cleaning the fields, clearing weeds around the banks and irrigation ditches, creating conditions for the soil to have time to rest or rotate crops… to cut the source of the disease.
– Selection of resistant varieties: However, at present, because high-quality varieties can be exported with little resistance or only temporary resistance, this factor depends on the conditions of each region to consider.
– Do not sow too thickly so that the rice plants are healthy and resistant to diseases (apply according to the amount of seeds recommended by the IPM, 1P5G, 3G3T programs). The best sowing density is 80-100 kg/ha.
– Apply fertilizer in a reasonable balance, do not apply excess nitrogen because when the rice has too much nitrogen, the leaves will be dark green and the leaf blade will not be upright but horizontal, making it very difficult for the leaves to photosynthesize. These are ideal conditions for fungal growth.
– Increase the application of fertilizers containing Calcium and Silicon to help the rice harden (thick internodes, close to the internodes), thick rice leaves to stand upright (rice leaves are not horizontal) to limit the rice leaves “catching” fungal spores. and prevent germinating fungal spores from entering.
– Manage not to leave the field with a lot of weeds because weeds are important hosts of the blast fungus.
– Regular monitoring of the field, especially in the stages of rice susceptibility to diseases (from the daughter rice stage to the growing stage), do not let the rice field be deprived of water.
– When the disease appears early, do not apply more nitrogen fertilizers, foliar fertilizers, growth stimulants and need to spray insecticides. It is recommended to use drugs containing active ingredients such as: Tricyclazole, Fenoxanil, Isoprothiolane … for high efficiency. If the disease pressure is high, it is necessary to spray twice again after 5-7 days.