“For greening, it would be really helpful,” Schacht says, “because it’s even harder to spot [visually] than canker.”
USDA researchers are not as far along with their work on greening detection as with canker, in part because of the technical challenges in establishing positive and negative plants for training and testing the dogs.
There are many other challenges as well.
Dogs tend to report more false positives for canker than false negatives. And in at least some cases of false positives—dogs indicating canker when the test-tree was known to be disease free—researchers later determined that a canker-infected tree was once on the site.
In enclosed areas, such as a citrus packinghouse, the dogs have been particularly adept at detecting even individual pieces of fruit that have canker. Still, their accuracy diminishes rapidly if the dogs get too hot and begin panting.
“It’s still not ready for prime time,” Gottwald says of citrus pest detector dogs as a commercially viable technique. “We need a lot more data and we need to see all of the caveats."