Study On The Construction Technology Of Low Epidemic Area Of Citrus Huanglongbing In The South Of Jiangxi

Citrus Huanglongbing(HLB),commonly known as citrus "cancer",seriously harms the development of citrus industry and brings destructive disasters to citrus industry.Gannan is the largest concentrated planting area of navel orange in the world.In recent years,due to the outbreak of HLB,a large area of citrus orchards have been destroyed,which has brought fatal harm to the healthy development of Gannan navel orange industry.So far,there is no cure for HLB.Once the citrus tree is infected with HLB,it has to be chopped down.In addition,diaphorina citri,the spread vector of HLB,is difficult to eliminate,causing the HLB difficult to be wiped out in the orchard.In this study,a low epidemic area was established by using regional management,monitoring diaphorina citri,digging out diseased trees and planting virus-free seedlings in the endemic areas of HLB in the citrus growing areas of south Jiangxi,and the corresponding technical system was integrated and demonstrated,preliminary forming the technical regulations of "Gannan citrus HLB low-endemic area construction".This paper focuses on the four aspects involving the effects of physiological and biochemical analysis on HLB-infected tree structure,monitoring and controlling of diaphorina citri,implementation of field natural heat cover and shoot tip grafting removal technology of HLB,as well as the establishment of HLB prevention and control system to study the construction technology of low HLB endemic area.The main results are as follows:1.By comparing the micromorphological characteristics,the content of photosynthetic pigment and malondialdehyde and the activity of three defense enzymes in the leaves of HLB-infected 'Newhall' navel orange with the healthy plants,it was found that the infection of HLB caused the tissue lesions in many parts of the host,which seriously affected the content of photosynthetic pigment and the degree of cell damage.2.The occurrence pattern of diaphorina citri was divided into four periods: the first stage was from the middle March to the early April,the second stage from the late May to the early June,and the third from the early August to the early September.The last stage is from the early October to the early November.The best control period can be divided into three stages: the first stage is in the initial stage of diaphorina citri,the control time is in the first ten days of March,the second stage is in the flourishing period of diaphorina citri,the control time is late May and early August,followed by last stage of diaphorina citri with the control time being mid-October.3.There was no systematic technique for the construction of low endemic area of HLB from2013 to 2015,making the susceptibility rate of HLB much higher,From 2016 to 2017,several methods involving the virus free seeding,monitoring and controlling of diaphorina citri,as well as the establishment of prevention and control system of HLB,were carried out,making the rateof HLB infection decreased obviously to 3.99% and 1.48%.,respectively.4.After 5 times heat treatment,the disease index of HLB tree in the treatment group was significantly lower than that in the control group.The symptoms and the concentration of the pathogen were obviously alleviated in the treatment group,the average value decreasing by 72%with the highest one by 99.9%,and the total yield of the value fruit of single fruit tree was decreased as well.The value fruit yield of the control group decreased most significantly with the average value fruit loss rate being 72.22%.Compared with the control group,the value fruit yield of the treatment group 3 decreased relative slowly with the average loss rate of value fruit being41.18%.The value fruit yield of treatment group 1 and treatment group 2 decreased slowly,which could maintain the yield of the previous year,and the average value of fruit loss rate was 17.71%and 14.52%,respectively.By grafting the stem tip of the infected scion,the surviving seedlings were not infected with the HLB pathogen by routine PCR analysis,and the removal effect was100%.