There is no medicine to cure after the onset of rice bakanosis

A number of readers in recent Fuyang, Huaiyin, and Anhui provinces have telephoned to report that rice seedlings have bastard disease.

Some serious rice paddy fields

On May 24th, Chen Guizhen of Zhenyang Town, Youyang County, came to the telephone to report that: Some local rice seedlings began to develop. The diseased and seedlings were more fine and tall than the healthy seedlings. The height of the plant was 15 cm, and the diseased plant rate was 20%. Rice seedlings are now in the 2-3 leaf stage and they were soaked with prochloraz before sowing. The rice variety is Gangyou 364. Local agricultural technicians diagnosed rice with bastard disease. She asked why the rice seedlings got this disease and how to use drugs to prevent it.

On May 26th, Lichun Lei of Xuliu Village in Huaiyin District of Huai'an City came to the telephone and said that 0.3 mu of dry rice seedlings developed. The diseased seedlings grew thinner and taller than normal seedlings, and their height was 3-4 times that of normal seedlings. Purple, the disease rate of 25%. The diseased seedlings and healthy seedlings are in the 2-leaf 1 heart stage. Soaking only with fresh water for 24 hours before sowing, there is no soaking of the drug, the variety is Gangyou 364. He asked what was wrong with rice.

Huang Biao, Handan City, Anhui Province, answered by telephone: 0.6-0.7 mu of water-borne rice seedlings developed bastard disease. The diseased seedlings were 5 cm higher than the healthy seedlings, and the diseased strain rate was 10%-20%. Now rice is in the 3-leaf 1 heart stage, so it is not soaked with pesticide before sowing. He asked whether it is now possible to use drugs to prevent bakanae in rice.

On May 29th, Sun Zhencheng, who was from Yuyang County, Fuyang County, came to the telephone to report that 30% of the 0.3 mu dry nursery seedlings had thin, high seedlings, about 15 cm higher than normal seedlings. The rice variety is Gangyou 364. Before sowing, soak in seeds in the seed packaging bag. He asked if the diseased rice seedlings could not be transplanted, and if it couldn't be transplanted, how would it be done?

On May 31, Zhang Guohua, Qianji Town, Suiyang County came to the telephone to report that some local rice fields were affected by drought-induced seedlings. The diseased plants were thin and high, 20 cm higher than normal seedlings, and the rate of severe field disease was 50%. At present, there are 2~3 leaf blades. Since there had been no bastard disease in the past, local farmers mostly did not soak seed before sowing. The rice variety is Gangyou 364. Consulting the seed production unit for the diagnosis of rice has bastard disease. He asked whether the rice had acquired bastard disease and how to control it.

No curative effect after bachelor disease treatment

It is understood that rice bastard disease can occur from the seedling stage to the heading stage. Seedling disease seedlings are higher than the healthy seedlings, and the leaves and leaf sheaths are slender, the leaves are pale yellow, and the roots are stunted. Some of the diseased seedlings die shortly before and after transplanting. The seeds with bacteria were the main source of infection, followed by rice straw. The pathogens adhere to the surface of the seed by conidia or latent in the seed by the mycelium to overwinter. During soaking of rice, pathogenic bacteria on diseased seeds can contaminate disease-free seeds. Studies have shown that the infectivity of rice bakanae pathogens is not strong, and Bacillus calycei mainly infects buds during germination. At this time, grain accumulation, suitable temperature and humidity, bastard disease carried by some grains A large number of spores germinated, not only infecting the original seed-bearing grain, but also impregnated the original non-contaminated grains, which greatly increased the infection rate. Generally, germination is more severe than non-germination. The longer the germination time, the heavier the disease.

Seeding of seeds with bacteria or covering with diseased rice straw will cause pathogens to invade the seedlings after the germination of the rice seeds, causing severe disease. Conidia produced on diseased plants can spread to healthy shoots and invade from stem wounds to cause reinfection. Although Bacillus kabaoensis can cause re-infestation, the pathogens mainly invaded in the early period of rice germination, and it is unlikely that field pathogens will infect healthy rice seedlings.

Seed soaking before sowing is the most effective measure to prevent bastard disease. The use of prochloraz, dithiocyano methane and other drugs and their solubilizers for soaking seeds have a good control effect on rice bakanae disease. Generally, it can be soaked with 25% prochloraz EC 2000-4000 times solution.

It is understood that the low dosage of prochloraz or the low drug concentration will lead to a decrease in the control effect, resulting in bachelor disease. Too short a soaking time can also lead to a decrease in control efficiency. Seed soaking for 48 hours under normal temperature conditions, soaking seeds for 60 hours at low temperature can guarantee effectiveness. In addition, the rice bakanae pathogen has produced a certain degree of resistance to prochloraz. When soaking seed with prochloraz, the dosage should be increased to improve the control effect.

Bacillus seedlings that have already developed bastard disease have no therapeutic effect when using fungicides. The diseased plants should be removed in time. Serious rice seedlings are not enough, if there are few seedlings, they can be transplanted by seedlings; if there are many seedlings lacking, they can use suitable varieties for direct seeding or interplanting in wheat fields. For the live-rice rice in Fuyang and other places, medium-maturing japonica rice varieties such as Wuyunjing No. 21 with a short growing period should be used, and the seeds should be sown before June 15.

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