Project Number: 6618-22000-030-20
Project Type: Trust

Start Date: Oct 25, 2007
End Date: Mar 31, 2009

Objective:
Determine biological and epidemiological characteristics of citrus HLB and its vector interactions and citrus canker in Florida environment, test various combinations of disease and vector control strategies, develop diagnostic methods, examine latency of transmission, determine effects on fruit quality, determine interaction with citrus psyllid and examine biocontrol potential.

Approach:
The project consists of seven of components. (1) Disease detection - Hyperspectral imaging will be evaluated as a method of detecting citrus infected by huanglongbing (HLB). Spectral images from diseased leaves and/or trees will be compared to those from healthy ones; the components of the spectrum that are characteristic of the disease will be identified; different scales of spectral analysis from individual lesions, individual leaves, canopy areas, whole trees, groves and regions will be tested; and a sampling strategy that would be effective for this technology will be developed. (2) Molecular genomics of Asian citrus psyllid ¿ the genomics of the psyllids will be elucidated with a primary goal of identifying genes and gene products of diseased and non-diseased psyllids. Genes of interest, especially those identified as possibly having a role in HLB acquisition, transmission, or replication, will be further analyzed using real time rtPCR in whole psyllids and cell cultures. (3) Culturing the huanglongbing bacterium ¿ This component has two subcomponents. One involves testing a psyllid cell culture as a culture medium for huanglongbing. The other involves analyzing and comparing the phloem composition of citrus, dodder and periwinkle. The outcome information will be useful in the development of a culture medium for HLB pathogens and artificial diet for Asian citrus psyllids. (4) Methods of transmitting huanglongbing for screening germplasm - Grafting experiments will be conducted with a range of cultivars differing in their reported susceptibility to huanglongbing. Inoculated plants will be monitored by real time PCR to determine % infection, time to detectable infection, relative titer of Liberibacter in the plants, and time to symptom development. Once developed, the method will be used to screen citrus species, cultivars, and budwood lines. (5) Sampling Asian citrus psyllid populations - Various traps will be assessed for their efficacy in detecting and monitoring adult psyllids. The value of a stem tap sampling method for adult psyllids will be studied. A hierarchical sampling plan for estimating population levels of psyllids will be investigated. (6) Southeast Asia guava effect for suppressing huanglongbing ¿ The efficacy reported in Vietnam of interplanting guava with citrus as a control strategy for Huanglongbing will be evaluated. Replicated studies will be established in commercial citrus to compare the citrus in monoculture to citrus interplanted with guava with respect to infestations of the psyllids and incidence and spread of HLB. (7) Citrus canker control ¿ The effect of windbreaks, copper sprays, and leafminer control on the increase and spread of citrus canker will be assessed in a commercial orchard located about 100 km south of São Paulo state, Brazil, in commercial citrus. Main effects will be windbreak versus no windbreaks. Citrus canker incidence will be estimated on multiple branches trees and evaluated as the number of leaves per branch infected. This will be a collaborative study with Fundecitrus and the University of Sao Paulo.