Early rice in Jiangxi province was transplanted in mid-April. In the next May to June, it will enter into rain season. According to previous records, probably in mid-May, leaf blast will begin to gradually occur.
Now we will talk about the prevention and control of the early rice’s leaf blast.
First of all, let’s recognize the symptoms and types of rice leaf blast.
Acute leaf blast:
Acute leaf spot lesions are dark green. In the beginning, it was water-soaked spots with white area in the middle and dark circles around it. More like burned plaque by hot water. These lesions are very likely to appear in some highly susceptible species, usually in persistent rain season or with high humidity in the field.
Chronic leaf blast:
The rim around the lesion is brown or tan, with white area in the middle and rhombus-shaped. A lot of small spots connect and form large dead spots. From the spots we can see the necrotic lines, poisoning part, necrosis part, and collapse part.
White point leaf blast:
It is harder to see in the field. In highly susceptible varieties, it occurs within one or two days. After two or three days, the white spots will turn to chronic lesions. This type of leaf blast will become chronic leaf blast at continuous high temperature.
Brown spot:
The size of the needle usually occurs when the disease resistance is strong and the weather is dry. Under suitable conditions of temperature and humidity, it can turn into a chronic lesion.
Acute and chronic leaf blast’s co-occurance
Leaf blastoccurrence conditions
1. There are enough pathogenic bacteria.
2. Susceptible rice varieties (hosts).
3. Suitable weather conditions for leaf blast’s occurance, moderate temperature (25-30 degrees), and high humidity (rainfall).
Prevention and treatment of leaf blast
1. Agricultural prevention and control: scientific nutrition and water management, rational application of nitrogen fertilizer, application of phosphorus and potassium fertilizers, application of silicon fertilizer, and supplementation of trace fertilizers. Excessive nitrogen fertilizer will cause soft leaves and more free amino acids synthesis. The disease can invade easily. Applying phosphorus and potassium fertilizers can increase the resistance, inhibit nitrogen fertilizer absorption, and leaf color will not be too dark green. Potassium fertilizer is also a synthetic element of some enzymes and can regulate rice physiological metabolites. Rice is also a silicon-prefering crop. Using silicon fertilizer can make the epidermis siliceous. The cell epidermis will be tough and the pathogens will not be easy to invade. Adding trace fertilizer can prevent yellow leaves and avoid resistance’ falling.
2. Chemical prevention and control: “Prevention as most important, comprehensive prevention and control”. Prevention before the onset of disease, control the disease timely after its onset. For the prevention, we can use like Pyraclostrobin, Tricyclazole, and Fenoxanil, etc.. Some farmers use high content Tricyclazole and mix with other products. The leaf tip may turn yellowish. So Tricyclazole 30% SC is recommended here than 75% WP because the safety is higher. Now Pyraclostrobin is more suggested to prevent leaf blast and it can also play a role in regulating plant growth. Observe the symptoms in the field and spray the products in advance.
After the onset of the disease, we will use the mixture of a protective product + curative product, such as Kasugamycin, Isoprothiolane with Pyraclostrobin, Tricyclazole or Fenoxanil. The dosage can be lifted according to the real situation or the efficiency may not be satisfied.
In order to enhance rice resistance and recover sooner, it can be combined with resistance agents and regulators such as Oligosaccharins.
Precautions
1. Prevent in advance. At early onset of the disease, right products should be applied timely to control the disease, so as not spread out.
2. Adhere to the principle of treatment + protection after the onset of the disease.
3. The spraying should do with enough water and uniformly. The infection center should be sprayed repeatedly.
4. Add silicone synergist to improve the efficiency.
5. The use of resistance-inducing agents and regulators is helpful for the control of the disease and the crops’ soon recovery.
6. In the dilution process, 2 times solution principle should be followed strictly to assure the efficiency.