Electronic noses, specialized machines that can be hand-held devices or for laboratory use, can detect emerald ash borer larvae while ash trees are still alive and before signs of insect infestations appear--as USDA Forest Service research shows.
“E-noses can detect emerald ash borer infestations early, when control treatments are most effective,” says Forest Service scientist Dan Wilson. “The e-nose technique would also be very useful in quarantine efforts.” Wilson led a study on the subject, which was published in the journal Biosensors.
Over the past 25 years, the emerald ash borer or EAB has killed at least tens of millions of ash trees in the U.S., attacking all species of ash, including white ash, green ash, and black ash.
Infested trees are stressed – branches die, bark splits, and epicormic branches sprout. On the tree-rating scale that Wilson and his team used, these stress signals would put a tree in a decline class of 3 or 4. The scale ends at class 5, when the tree is dead.
Long before stress is visible, the tree’s smellprint is profoundly altered. Smellprints are distinctive e-nose response patterns to volatile organic compounds or VOCs.
Even though EAB larvae only tunnel shallowly into the sapwood, they cause significant damage that changes the physiology of the entire tree. The damage changes the sapwood VOCs released, and consequently, changes the tree’s smellprint.
“Trees that are infested with EAB should be marked for immediate harvest unless control treatments will be applied,” says Wilson. “Immediate harvest of infested trees would preserve the monetary value of the lumber by avoiding damage from secondary insect borers, wood-decaying fungi, and other decomposers.” The early harvest of infested trees could also help slow the spread of EAB.
One of the most important prevention strategies is to not move firewood.
Ash samples for the study came from a green ash plantation in Arkansas. Benjamin Babst and Mohammad Bataineh collected 86 samples, which were frozen and shipped to Wilson’s lab at the Center for Bottomland Hardwoods Research.
Wilson and his team used a dual-technology e-nose, which combines sensor arrays with the power of gas chromatography for chemical detection. “E-noses have revolutionized the discipline of pathology,” says Wilson, who has published extensively on using e-noses to detect disease in plants, animals, and humans.