Chemical Ecology of Rapid ʽŌhiʽa Death
We are working on understanding the chemical ecology of Rapid ʽŌhiʽa Death (ROD), which is critical for protecting both healthy and ROD-infected ʽōhiʽa. A better understanding could lead to early ROD detection tools and the development of attractants and repellents to manipulate ambrosia beetle populations.
What is Rapid ʽŌhiʽa Death (ROD)?
Rapid ʽŌhiʽa Death—ROD—is a devastating disease that afflicts ʽōhiʽa (Metrosideros polymorpha), the most widespread and abundant native tree in Hawaiʽi. ROD is a fatal vascular disease caused by two newly identified fungi, Ceratocystis lukuohia and Ceratocystis huliohia. Both species of fungi will kill ʽōhiʽa, although C. lukuohia is more aggressive.
ʽŌhiʽa cover 250,000 acres of forest in the state of Hawaiʽi and at least one million ʽōhiʽa trees have died from ROD. We do not fully understand the interactions between the Ceratocystis fungi and invasive ambrosia beetles—in the Xyleborini tribe—that spread ROD.
ROD-infected ʽōhiʽa provide a home and breeding space to several types of invasive ambrosia beetles. The beetles produce frass containing viable Ceratocystis and can carry viable fungal spores that spread and kill ʽōhiʽa.
Management strategies to prevent the spread of ROD could improve survival of Hawaiian ecosystems and understanding the chemical ecology of the disease can assist managers in developing these strategies.
Objectives:
This tiny (3-5 millimeter) invasive ambrosia beetle Xyleborus ferrungineus, produces the most frass from ROD infected ʽōhiʽa trees. Frass, a beetle boring dust, contains wood particles, dead beetle parts, and feces. Photo: K. Roy, 2022.
- Test how well repellents work to deter ambrosia beetle attacks to ʽōhiʽa trees with and without ROD.
- Identify fungi associated with ROD and invasive ambrosia beetles and fungi associated with native ambrosia beetles.
- Test ambrosia beetle behavior in response to chemical cues, to determine their level of attraction to Ceratocystis fungi.
- Identify volatile organic compounds—emitted gases—associated with ROD infected ʽōhiʽa under stress. Characterizing volatile organic compounds can help in the development of early detection tools and mechanisms to potentially manipulate beetle populations.
Beetle still-air olfactometer
Beetle still-air olfactometer set-up. Olfactometers are devices that produce odor stimuli to a test subject—i.e., Ambrosia beetle—in a standardized manner with determined air-flow, odor concentration, and time settings.
Collecting leaf volatiles
Leaf volatiles collected from ROD-infected ʻōhiʻa saplings. Collecting leaf volatile organic compounds helped us characterize them for early detection and potential beetle behavior manipulation. Volatile compounds are emitted as gases from solids.
We are working on understanding the chemical ecology of Rapid ʽŌhiʽa Death (ROD), which is critical for protecting both healthy and ROD-infected ʽōhiʽa. A better understanding could lead to early ROD detection tools and the development of attractants and repellents to manipulate ambrosia beetle populations.
What is Rapid ʽŌhiʽa Death (ROD)?
Rapid ʽŌhiʽa Death—ROD—is a devastating disease that afflicts ʽōhiʽa (Metrosideros polymorpha), the most widespread and abundant native tree in Hawaiʽi. ROD is a fatal vascular disease caused by two newly identified fungi, Ceratocystis lukuohia and Ceratocystis huliohia. Both species of fungi will kill ʽōhiʽa, although C. lukuohia is more aggressive.
ʽŌhiʽa cover 250,000 acres of forest in the state of Hawaiʽi and at least one million ʽōhiʽa trees have died from ROD. We do not fully understand the interactions between the Ceratocystis fungi and invasive ambrosia beetles—in the Xyleborini tribe—that spread ROD.
ROD-infected ʽōhiʽa provide a home and breeding space to several types of invasive ambrosia beetles. The beetles produce frass containing viable Ceratocystis and can carry viable fungal spores that spread and kill ʽōhiʽa.
Management strategies to prevent the spread of ROD could improve survival of Hawaiian ecosystems and understanding the chemical ecology of the disease can assist managers in developing these strategies.
Objectives:
This tiny (3-5 millimeter) invasive ambrosia beetle Xyleborus ferrungineus, produces the most frass from ROD infected ʽōhiʽa trees. Frass, a beetle boring dust, contains wood particles, dead beetle parts, and feces. Photo: K. Roy, 2022.
- Test how well repellents work to deter ambrosia beetle attacks to ʽōhiʽa trees with and without ROD.
- Identify fungi associated with ROD and invasive ambrosia beetles and fungi associated with native ambrosia beetles.
- Test ambrosia beetle behavior in response to chemical cues, to determine their level of attraction to Ceratocystis fungi.
- Identify volatile organic compounds—emitted gases—associated with ROD infected ʽōhiʽa under stress. Characterizing volatile organic compounds can help in the development of early detection tools and mechanisms to potentially manipulate beetle populations.
Beetle still-air olfactometer
Beetle still-air olfactometer set-up. Olfactometers are devices that produce odor stimuli to a test subject—i.e., Ambrosia beetle—in a standardized manner with determined air-flow, odor concentration, and time settings.
Collecting leaf volatiles
Leaf volatiles collected from ROD-infected ʻōhiʻa saplings. Collecting leaf volatile organic compounds helped us characterize them for early detection and potential beetle behavior manipulation. Volatile compounds are emitted as gases from solids.