How to prevent and control common rice pests and diseases? A detailed practical guide
Rice bacterial leaf blight is a bacterial disease of rice leaves. The pathogen is Xanthomonas oryzae pv. oryzae in the prokaryote kingdom. The bacterium invades through wounds and water pores in the roots, stems and leaves, and reproduces and causes damage in the vessels of the vascular bundles. Seedlings and tillering stages are the most susceptible. Seedling leaves mostly show leaf blight symptoms. In susceptible varieties...
Rice bacterial leaf blight
A bacterial disease of rice leaves. The pathogen is Xanthomonas oryzae pv. oryzae in the prokaryote kingdom. The bacterium invades through wounds and water pores in the roots, stems and leaves, and reproduces and causes damage in the vessels of the vascular bundles. Seedlings and tillering stages are the most susceptible. Seedling leaves mostly show leaf blight symptoms. On susceptible varieties, acute wilt symptoms often appear, with lesions being grayish-green and water-soaked, and diseased leaves quickly curl and wilt; on resistant varieties, brown necrotic spots form. The optimum temperature for the pathogen's development is 26°C-30°C. It overwinters on diseased residues, and rice seeds can also carry the bacterium; it spreads through wind and rain. Fields with excessive nitrogen fertilizer and low-lying waterlogged areas develop the disease earlier and more severely. After typhoons and heavy rain, the disease often spreads rapidly on susceptible varieties. Control measures: selecting and planting resistant varieties and preventing rice fields from flooding are key to disease prevention, combined with chemical control.
Rice bakanae disease
Also known as white stalk disease, it is a fungal disease of the aboveground parts of rice. The pathogen is Gibberella fujikuroi in the Ascomycota subdivision. Its asexual state is Fusarium moniliforme in the Deuteromycota subdivision. The disease can occur from the seedling stage to the heading stage. Diseased plants grow excessively tall, are spindly and yellowed, and are usually 3-10 cm taller than healthy plants, making them very easy to identify. The basal nodes of diseased plants often have adventitious roots growing upside down, along with a pink mold layer. The optimum temperature for the pathogen's development is around 25°C, and seeds carry the bacterium. Selecting disease-free seeds or soaking seeds with chemicals before sowing is the key control measure.
Rice sheath blight
For affected rice fields, apply chemicals when the proportion of diseased plants reaches 30%-4% at the booting stage. The spray solution should be applied to the middle and lower parts of the rice plants. With the splash-irrigation method, a 3 cm-5 cm water layer should be maintained in the field. When applying jinggangmycin, it is best to do so on a sunny day after rain, or when there is no heavy rain within two hours after application. Use 100 ml-150 ml of 5% jinggangmycin aqueous solution per mu, or 25 g of high-concentration jinggangmycin powder, choosing either one, and dilute with 100 kg of water for conventional spraying, or dilute with 400 kg of water for splash irrigation.
Rice stem borers
The focus should be on controlling the second generation of the second-brood striped stem borer and, in some areas, the second generation of the third-brood striped stem borer, with rice fields from the booting stage to before full heading as the key targets. Broadcast 1 kg-1.5 kg of 5% dimehypo granules per mu, or use 150 ml-200 ml of 25% dimehypo aqueous solution per mu, or 100 ml of 25% dimehypo aqueous solution plus 100 ml of BT emulsion, choosing either one, and dilute with 60 kg-75 kg of water for conventional spraying, or dilute with 5 kg-7.5 kg of water for low-volume spraying.
Rice planthoppers
Apply chemicals when the peak of young nymphs is reached and the number of insects per 100 hills reaches more than 1,500. When applying, start from the edges of the field and move from outside to inside to encircle and wipe them out. Spray evenly and thoroughly, and be sure to apply the solution to the middle and lower parts of the rice plants. Use 20 g-25 g of buprofezin wettable powder, or 20 g-25 g of 25% buprofezin wettable powder, or 150 ml of 20% isoprocarb emulsifiable concentrate, choosing either one, and dilute with 75 kg-100 kg of water for conventional spraying, or dilute with 5 kg-7.5 kg of water for low-volume spraying.
Rice skipper
With late middle-season rice fields as the focus, apply chemicals when the peak of young larvae is reached and there are 10-20 insects per 100 hills of rice. Use 75 g-100 g of 90% trichlorfon crystals per mu, or 100 ml-250 ml of 50% fenitrothion emulsifiable concentrate, or 150 ml-200 ml of BT emulsion, choosing either one, and dilute with 75 kg-100 kg of water for conventional spraying, or dilute with 5 kg-7.5 kg of water for low-volume spraying.
Rice leaf roller
Focus on controlling the main damaging generation. At the young larval stage, apply chemicals when there are 15-20 newly rolled small larval shelters per 100 hills of rice, or 20 insects per 100 hills at the heading stage. Use 150 ml-200 ml of 25% dimehypo aqueous solution per mu, or 72 ml of 50% fenitrothion emulsifiable concentrate, choosing either one, and dilute with 60 kg-72 kg of water for conventional spraying, or dilute with 5 kg-7.5 kg of water for low-volume spraying. The best time to apply is in the evening.
Vigorously promote the new technique of using triadimefon at the heading stage. At the booting stage of rice, use 50 g-100 g of 15% triadimefon wettable powder per mu, diluted with water for conventional or low-volume spraying, which can effectively prevent premature aging of hybrid rice and also control various diseases at the heading stage such as rice sheath blight, rice false smut and rice kernel smut.