Exploration Of The Spectrum Monitoring Technology Of Huanglongbing And The UAV Control Technology Of Citrus Psyllid

Huanglongbing(HLB)or citrus greening disease transmitted by the Asian citrus psyllid(Diaphorina citri)has been one of the most destructive plant diseases and caused huge losses in citrus production worldwide.It is very improtant for effective control the spread of HLB and reducing its harm to establish the highly-efficient and real-time HLB diagnosis and controlling technology of ACP.Therefore,the technologies of spectral detection of citrus HLB and the UAV control technology of citrus psyllid were conducted in this research.The yellow and green leaves from HLB-infected and healthy citrus trees of cocktail grapefruit(C.paradis Macf.)were collected to determine the starch content and hyperspectral reflectance.The correlation between starch content and HLB infection was analyzed.A group of sensitive characteristic spectra of HLB were selected and the predictive ability of prediction model based on the characteristic spectral bands for HLB was studied.The effects of citrus tree-shape,cruising altitude and speed of UAV sprayer on the droplet distribution in citrus tree canopy were explored,and the influence of the spray additives of methylated vegetable oil,sodium esters and organic silicon on the water drops diffusion performance of aerosol spray were also evaluated.In all,we put forward the UAV spray technology of the pest control for the citrus orchard,such as UAV flight parameters,supporting agronomic techniques and high efficiency spray additives,etc.In the orchard conditions,the control effect of the UAV sprayer and other plant protection technology on the citrus psyllid and leaf moth was tested and verified the effectiveness,efficiency and benefits of the UAV and other plant protection spraying methods on the leaf moth and psyllid were evaluated.These resμlts provide a data support and theoretical basis for the application of these techniques in citrus production.The main resμlts as follows:1.Although the starch content in the leaves from HLB-infected citrus trees increased significantly,HLB tree were hardly distinguished from the healthy plants by starch content determination because the HLB recognition accuracy was only 27% and 13% from yellow and green HLB leaves,respectively,but the recognition accuracy of healthy leaves was 97% and 100% for yellow and green of healthy leaves,repectively.2.By analyzing the visible and near-infrared hyperspectral information of the leaves from HLB infected and healthy plants,the spectral bands of 557,646,748,776,996,1004,1535,1585,1748 and 1887 nm were selected as the characteristic spectral bands of HLB recognition.The HLB prediction model of the least square-support vector machine based on the characteristic bands is constructed,and the identification accuracy of the HLB infected leaves from the modeling and prediction set leaves samples is 97.9% and 96.6% respectively.3.Compared with several additives,such as methylated vegetable oil,alkyl ether,sodium ester and organic silicon,the organic silicone additives showed better wet and spread effect on the citrus leaves.In addition,the compound solution of 100 times glycerin and 500 times organic silicone additives can significantly prolong the evaporation time and increase the droplet coverage.4.In the same case as other operating parameters,the coverage rate of spray droplets on the leaf surface decreases with the increase of the UAV sprayer flying speed,and vice versa.As the height of UAV flight increased,the coverage rate of the drops decreased correspondingly and the difference of drop distribution in the canopy space increased.In our experiment,when the UAV spraying operation height h=1.0m and the flying speed v=1.7m/s,the variation coefficient of the drops coverage rate on the leaf was the smallest and its drop coverage rate was 19 % in the open canopy.These parameters can be used as an ideal UAV sprayer operating standard for the control of the citrus psyllid and leaf moth.5.In UAV flight speed 1.7 m/s,height of 1.0 m condition,the control experiment of the citrus psyllid and leaf moth by UAV sprayer showed that the control effect of citrus psyllid in the more densely planted orchard was 96.7% at 24 h after the UAV applying pesticide and 100% at 72 h after the UAV spraying,and the control effect of leaf moth was 84.6% at 7 days after the UAV spraying.Compare the citrus citrus psyllid and leaf moth control efficiency of UAV sprayer,artificial spraying system and target spraying mechanism in the orchards with wider row spacing and dense plant spacing,the resμlts showed that all of the citrus plants with three kinds of protection spraying does not found the citrus psyllid throughout the year and the annual average harm ratio of the leaf moth was lower than 0.02 leaf/shoot.The control effect of three kinds of spraying methods no significant difference.6.Investigation and contrast analysis of the pest control effect,working efficiency and economic benefits of the citrus orchard with three kinds of spraying methods,the resμlts show that,for the prevention of the citrus psyllid and leaf moth,the control efficiency of UAV sprayer is 45 times of manual operation,and 6 times of target spraying mechanism.The pesticide amount consumed by the UAV spraying is only about 10% of the manual spraying and 50% of the target spray machine.It can be seen that the UAV spray technology has better application prospects for the pesticide reduction and labor-saving and efficient cμltivation management in the citrus orchard.