Indirect testing could help catch huanglongbing disease early in a citrus tree, but experts recommend using a combination of detection methods for management of the disease.
Current testing for huanglongbing (HLB) infected trees can be a challenge as indirect testing can be too sensitive, showing a false positive. Direct testing methods can miss the bacteria in the tree, thus showing a false negative. University of California Davis Professor Carolyn Slupsky says all of the detection methods should be used together for best management of the disease. “So there’s not one specific test that is the best,” Slupsky says. “I think if we start to use them together, then you start to increase the specificity on the sensitivity of the tests.”
Slupsky relates the process to a person’s trip to the doctor’s office. “For example, if you think about it in terms of human diagnostics, very rarely does the physician come in and tell you right off the bat that you have something,” Slupsky says. “It’s one of those things where you start off with this broad thing and then you start to whittle it down. In the same way I think we can look at this disease. We can take something that’s a very sensitive test, even if there are a lot of false positives, and then what we can do is find areas where it looks like there might be a hot spot. Then we do some intensive sampling there by bringing in the direct testing methods. Once we start to the intensive sampling, we have more of a chance of picking up that disease and we can verify that’s what we’re seeing in that area.”