Researchers have found a fast and low-cost staining method to diagnose Citrus Huanglongbing (HLB), potentially helping to mitigate crop loss. The method identifies insect feeding sites, which are the transmission agent. The sites can then be tested for the causal agent (Candidatus Liberibacter asiaticus) using a quantitative real-time polymerase chain reaction. This allows HLB to be identified up to two days after transmission, instead of the months traditionally needed.
HLB, also known as greening, is incurable and causes trees to produce bitter fruits that are green, misshapen, and unsuitable for sale. As the most effective methods to stop HLB spread involve early diagnosis, it is imperative that growers have access to a reliable technique.
The strategy for diagnosing HLB before the appearance of blotchy mottle symptoms was devised by Professor Nian Wang and his postdoctoral research associate Dr. Sheo Shanker Pandey, both from Citrus Research and Education Center, Department of Microbiology and Cell Science, at the Institute of Food and Agricultural Sciences of University of Florida.
This method allows the HLB causal agent to be detected long before the appearance of symptoms. Meanwhile, traditional methods rely on waiting for blotchy mottle symptoms to occur and then confirming disease presence using molecular tools. However, as symptoms typically do not occur for many months, the disease has ample opportunity to spread throughout the grove. This makes it difficult to prevent the spread of HLB through measures such as quarantine, controlling the insect that spreads the disease (Asian citrus psyllid), removing diseased trees and planting HLB-free trees.