Relating Visual Symptoms of Greening to PCR Results Ron Brlansky

Background on HLB Symptoms HLB means “yellow shoot” hence the first symptom usually found is the yellow shoot Depends on the tree age and time and stage of infection If infection occurs early in tree life it may progress over the whole canopy If infections occurs at a later stage the symptoms may be confined to a sector

If a sector is infected then only those parts may show symptoms/rest of the tree may be normal Range of symptoms can be found on infected trees: heavy leaf and fruit drop, off season flushing and blooming, stunted trees, sparely foliated, twig dieback Yellowing, then blotchy mottle (the characteristic symptom)

What about leaves with yellow midveins, chlorotic patterns resembling Zn, Fe, Mn, Ca, S deficiencies, green island symptom? Part of the syndrome, but are they PCR +? Most reliable symptom? Small lopsided fruit with curved columella, aborted seed and salty bitter taste

Where are We Now? Irey et al (2006) “non specific nature of the foliar symptoms makes the disease difficult to distinguish from nutritional deficiencies and other plant diseases based on symptoms alone” PCR is necessary for confirmation of the field identification

Irey: “Although PCR methods are sensitive and specific, consistent detection of the HLB pathogen…problematic.. because of the low concentration and uneven distribution of the pathogen in host plants”

Conclusions Still need to know more about the distribution of Las in trees and relationship to symptoms; Where and when to sample? More info is needed (time of year, location, growth stage) PCR is still a necessary and valuable tool for detection ; can even detect bacteria in asymptomatic infections

“more infections can be detected by combining visual detections and real-time PCR than by either method alone” Irey et al, Proc. Fla. State Hort. Soc. Pp

Keep inspecting for greening symptoms Have suspected samples verified by PCR A combination of visual symptoms with confirmation by PCR is the best for now