Physiological blue-green in rice has been more common in rice-wheat cropping areas in Jiangsu in recent years, and concentrated in rice filling stage, which has a great impact on yield.

Disease occurrence

The rice plants with disease symptoms at the grain filling stage suddenly lost water and blighted, the leaves were wilting, grayish blue, and there were no spots; the stems were dry and contracted and the plants were lodging; the hulls were grayish blue and formed into a valley; the roots became yellow and black. Often within 1-2 days suddenly occur in large areas. Blue dry death is the sudden death of the whole burrow, which occurs in the field in a flaky form. It can be distinguished from the single stem defoliation and death of insect pests, and is distinguished from the progressive death of pathological diseases.

Most of the occurrences occurred in late September to early October, and the symptoms were acute and sudden. In case of sudden onset of sudden changes in temperature, the field is well developed and the symptoms and loss levels will vary depending on the time of occurrence. There are differences in the incidence of different rice varieties, usually the big ear type and the lodging-prone varieties suffer more.

Hazardous loss The occurrence of rice bacterial wilt occurs at the grain filling stage, which has a greater impact on the yield, makes the rice lodging, shortens the grouting time, and matures in advance. The earlier the general disease is, the greater the loss is, and the main manifestation is that the seed setting rate and dry weight decrease significantly.

Cause of disease

1. Rice and wheat long-term continuous cropping. In the Chuzhou region, rice cultivation is the main form of rice cultivation. Many years of large-area, no-tillage wheat cultivation and light shallow cultivation of rice have led to shallow cropping, poor soil permeability, reduced fertility and water holding capacity, and unfavorable rice growth.

2. Soil fertility decreased. The input of organic manure in farmland has been reduced year by year. The amount of N, P and K compound fertilizers in a few plots has also been less, and the amount of nitrogen fertilizer has been increased. As a result, soil fertility has declined, and rice has become prematurely decayed.

3. Rice root distribution is light in light cultivation mode. In recent years, light rice cultivation methods such as throwing rice seedlings and direct seeding have a large area. The disadvantages are that rice roots are distributed in shallow soil layers and are easily affected by the external environment. When the air temperature suddenly changes at the heading stage, the water absorption capacity of the roots is poor, and physiological characteristics are easily generated. Blue and dry.

4. The sudden change in temperature is a direct cause. Rice is a thermophilic plant, and the suitable temperature for indica rice during filling is 20-28 °C. In recent years, due to the expansion of light-cultivated paddy fields in Chuzhou, the growth period of rice has generally been postponed. From late September to early October, it is the grain filling period. At this stage, the temperature changes greatly, and the minimum temperature can fall below 13°C. For example, two cooling processes occurred in late September and early October 2008, and the minimum temperature dropped to 11.9°C on October 8. Under low temperature conditions, the resistance of rice decreased, and the weather became fine after rainy weather. The temperature rose sharply and the transpiration accelerated. This caused physiological water loss and led to the sudden death of green crops.

Prevention measures

1. Improve the farming system. Under the circumstance that no less ploughing has been basically popularized, deep ploughing will be implemented. In autumn sowing, rotation ploughing, cultivating once every 2-3 years; when farming rice, cultivating one-time rotary cultivating for deep plowing and then plowing the second plowing tillage. With light and simple planting methods such as throwing seedlings and direct seeding, it is necessary to do a good job of turning cultivation and deep plowing. In order to avoid cold temperatures, sandy soil plots should be improved and improved by hand-planting rice cultivation methods and using rice varieties that are mature in early stages.

2. Increase soil fertility. Through the increase of organic fertilizer, balanced fertilization and other measures to change the partial application of nitrogen fertilizer and nitrogen fertilizer in the late high status, so that reducing nitrogen and phosphorus fertilizer add fertilizer.

3. Strengthen cultivation management. Choose rice varieties with deep roots and strong resistance; rice crops will be increased at the mid-growth stage to promote the timely deduction of roots; long-term deep-water irrigation will be avoided; gap irrigation will be maintained after heading, hard water plates will be used, and water will be used to regulate root growth and enhance root activity. The last time the horse is watered 7-10 days before harvesting, the water can be cut off;

4. Spray the foliar fertilizer at the ear stage, protect the leaves and raise the roots, and enhance the plant resistance.

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