Research On Biological Characteristics Of Rice Infected By Ustilaginoidea Virens,and Green Control Of Rice False Smut In Eastern Zhejiang

Rice false smut(Ustilaginoidea virens(Cooke)Takahashi)is a fungal diseas.Rice false smut not only reduces the yield of rice,but the toxin produced by rice false smut has teratogenic effects on humans and animals.In recent years,affected by global climate change,large-scale promotion of hybrid rice,and changes in farming methods,the occurrence of rice false smut has continued to increase,and it has become an urgent problem to be solved in rice production.The average panicle rate of rice false smut in Taizhou is 6.4%,and the incidence rate of some varieties is as high as 20%.The systematic research on rice false smut in eastern Zhejiang is imminent.Through years of field investigations and laboratory experiments,this paper deeply studies the biological characteristics,occurrence and damage laws,epidemic factors,early warning technology and green prevention and control technology of rice false smut pathogen in eastern Zhejiang,which provides reference for local practical application.The main findings are as follows.1.Biological characteristics of rice false smut pathogen in eastern Zhejiang: PSA was the most suitable medium for rice false smut.The optimum growth temperature was 28°C.The optimum growth pH was 6.Light basically had no effect on mycelia growth.The culture time was preferably7-9 days during the rapid growth period.2.Occurrence and damage law of rice false smut in eastern Zhejiang: All 20 rice varieties mainly planted in Zhejiang Province could be infected with rice false smut,and the growth laws of rice smut were different among different rice varieties,but they all conform to the Logistic function.Rice false smut mainly damages the middle and lower part of the panicle,and there was a linear regression relationship between the number of rice smut balls per panicle and the yield loss rate,and the yield decreases by 4.7%-6.2% when the number of rice smut balls increases by 1 grain.The number of rice smut balls per panicle was negatively correlated with the number of solid grains,panicle weight and1000-grain weight,and positively correlated with the empty chaff rate.The principal component analysis showed that rice false smut affected rice yield loss by reducing the panicle weight.3.Factors influencing the occurrence and prevalence of rice false smut in eastern Zhejiang: The occurrence of rice false smut in eastern Zhejiang was closely related to climate conditions,nitrogen fertilizer dosage,and rice varieties.Low temperature and high humidity were conducive to the prevalence of rice false smut,and increasing the amount of nitrogen fertilizer would aggravate the occurrence of rice false smut,and the occurrence of rice false smut in direct seeding fields was more serious than that in machine-seeded fields.Comprehensive evaluation of rice false smut resistance of12 rice varieties showed that conventional japonica rice had the strongest field resistance to rice false smut,hybrid rice was generally more susceptible,and indica-japonica hybrid rice had the weakest resistance.4.Early warning technology of rice false smut in eastern Zhejiang: Different sowing periods would affect the occurrence of rice false smut,and the occurrence of rice false smut was most serious at the end of May.A meteorological early warning model was established,the occurrence rate of rice false smut and the number of days with average temperature below 28°C in the second half of August fit the Logistic function.The release of spores in the field was mainly concentrated in the morning,showing dynamic fluctuations,and the amount of spores in the field reached its peak 1 week after the rice was fully eared.5.Green prevention and control technology of rice false smut in eastern Zhejiang: Four types of biocontrol bacteria were able to control rice false smut,including Bionectria ochroleuca 1-3,Penicillium oxalate 2-1,Aspergillus fumigatus 5-T,and Gliomastix 5-62.The control effect of high-dose biocontrol bacteria on rice false smut was better than the low-dose.There were differences in the optimum control period of pesticides with different action mechanisms.Tebuconazole and Jinggangmycin sprayed 1 week before rice breaching and 1 week after full earing had the best disease control effect,and Tebuconazole 2 weeks before breaching and Jinggangmycin at the breaching stage also had better effects.Tefluthrin was the most effective when applied only 1 week before the break.