The Occurrence Regularity Of Diaporthe Citri And Green Control In Hongjiang City

Diaporthe citri is one of the primary diseases among citrus fruits,which seriously affects the appearance and commodity value of the fruit.To clarify the situation of this disease in Hongjiang City,Hunan Province,and establish a green control system,this paper conducts a systematic investigation in the main citrus production areas of Hongjiang.By separating and identifing Diaporthe citri pathogen,The pathogen of Diaporthe citri was tested in laboratory and the field efficiency test was conducted.this paper provides a green control technique for Diaporthe citri in Hongjiang City.The main results are as follows:1.Research on occurrence pattern of Diaporthe citri in HongjiangIn 2018 and 2019,an investigation was conducted on sugar orange in two orchards in Hongyan Town and Shuangxi Town of Hongjiang City.In the systematic research of Diaporthe citri Hongjiang City,it was found that the pathogenesis generally occurred from May to September.The peak period was from June to July.In which leaf disease development faster,the fruit disease was severe,and the branches were in the middle.The early stage of Diaporthe citri is from late April to early May.May-June is the summer shoot sprouting stage,in which leaf disease development faster.Fruit infection began in late May,which is the young fruit stage of citrus.The month from late June to late July is the fruit enlargement stage,the incidence of citrus fruit is faster.Overall,in 2018,2019,the occurrence pattern of Diaporthe citri in Hongjiang City,basically no significant difference,showing a downward trend.Different species of citrus infected with Diaporthe citri have different situations.Sugar orange gets infected earlier and more severely.The navel orange began to contract the disease in late April,with a moderate incidence.Wenzhou tangerine contracted the disease relatively late,and the incidence is relatively light.2.The fungicide pyraclostrobin with better inhibitory effect on Diaporthe citri colony in Hongjiang City was selected.The indoor toxicity of four different fungicides to Diaporthe citri colony was determined by the growth rate measurement.The four fungicides had various inhibitory effects on Diaporthe citri colony and showed apparent inhibitory effects.According to their inhibitory effects,four fungicides ranked in descending order:pyraclostrobin>tebuconazole>mancozeb>benzopyrazate.Among them,250 g/L pyraclostrobin EC had the most apparent inhibitory effect on mycelial growth,and its EC₅₀value was 0.187 mg/L.3.The prevention and treatment plan of Diaporthe citri was optimized.In 2019,a comprehensive control experiment on citrus scab was carried out in the orange orchards of Shuangxi Town and Hongyan Town in Hongjiang City.According to the treatment zones,four formulations were set and applied in the orchards of the selected experimental area.Each treatment area was five-acre,and 300 kg of spraying liquid per acre was sprayed four times a year.By comparing the disease index,relative control effect and economic benefit of different formulas,formula 1（80%mancozeb wettable powder 300times 500 g/mu+99%mineral oil 200 times 750 ml/acre）had good control effect in the experiment.The relative control effect reached 82.3%.The fruit surface was clean,and the proportion of grade 0 and grade 1 fruit was relatively high,and the ideal control effect was achieved.The control effects of Formula 2,Formula 3 and Formula 4 were 80.1%,77.1%and 70.7%,respectively.By comparing the cost of four formulations and comparing the sales price of Citrus in 2019,Formula 1 increases revenue most among the four formulas.4.Combined with the actual situation of Hongjiang City,the demonstration and promotion plan of green control of Diaporthe citri disease was formulated:garden cleaning in winter and spring,appropriate pruning,enhancing ventilation and light transmittance,rational fertilization to enhance tree vigor,prohibiting the application of glyphosate and chemical control technology.