What investigations have been conducted on citrus greening disease in my country?

Fixed-site investigation

The first is the investigation of the disease evolution process of diseased trees at different levels in the field: Located in Dong'ao Village, Shangyang Township, Huangyan District, a diseased orchard with normal psyllid control was selected. , 100 diseased trees with different disease levels were identified and marked, and the evolution of different disease levels and disease index changes were investigated in early November of each year from 2002 to 2007, and the disease evolution process between years was analyzed. The second is a survey on the spread of the epidemic under uncontrolled conditions: Located in Pingtian Village, Pingtian Township, Huangyan District, a survey on the occurrence of the epidemic was conducted from 2003 to 2007. The number of citrus plants planted in the village, the number of diseased plants, the rate of diseased plants, and the growth rate of diseased plants were measured. The indicators were investigated and analyzed, and the disease strain rate index was used to conduct statistical simulation of the epidemic development trajectory, and a model of epidemic spread under uncontrolled conditions was established.

Epidemic survey

From 2002 to 2007, we seize the critical period from October to December every year when the symptoms of Huanglongbing’s “mottled yellow leaves” and “red-nosed fruit” are most obvious. Through technical training and on-site guidance, we train the epidemic census team with the backbone of township (street) agricultural technicians, village cadres and plant protection workers, in accordance with the principle that "townships (towns) do not miss villages, villages do not miss households, households do not miss gardens, households do not miss gardens, According to the requirements of "no blocks are missed in the garden and no plants are missed in the blocks", comprehensive inspections and markings are carried out. The survey data is based on the village and is registered by household to provide a scientific basis for identifying the epidemic situation and removing diseased plants. At the same time, it is advocated to carry out epidemic census and eradication of diseased strains simultaneously to reduce the rate of missed inspections and ensure the quality of census and prevention and control. On this basis, the research team organized technical forces to conduct random inspections and verifications in each township (street), and promptly corrected and provided guidance when problems were discovered to ensure that the survey data were authentic and reliable.

Investigation on the disease evolution process

The disease evolution process of diseased trees at different levels in the field: From 2002 to 2007, a diseased orchard was selected in Dong'ao Village, Shangyang Township, Huangyan District (for psyllid control) , identify 100 diseased trees with different disease levels and mark them, investigate the evolution of different disease levels and disease index changes in early November every year, and analyze the disease evolution process during the year (disease grading standard: Level 0: no disease on the tree; Level 1: no disease on the tree) There are 1 to 2 tips with mottled yellowing leaves; Level 2: Part of the side branches or main branches have mottled yellowing symptoms, and the symptomatic branches account for less than 1/3 of the whole tree; Level 3: The symptomatic side branches or main branches account for less than 1/3 of the whole tree. More than 1/3 and less than 2/3; Level 4: Symptomatic branches are more than 2/3; Level 5: The whole tree is dead).

Investigation on damage and yield loss

In November 2006, 49 15-year-old orchards were randomly identified in Yuanqiao, Shabu and other places in Huangyan District (one of them was treated as disease-free Well-managed orchards as controls), randomly survey 30 orange trees in each orchard, calculate the diseased plant rate of each treatment, and then conduct a survey on the number of normal fruits per tree in the selected 30 orange trees, and convert the plant yield at 10/kg. The yield loss rate of each treatment was calculated by comparing with the control orchard.