Insects as Vectors of Rapid ʽŌhiʽa Death - ROD -
Wood-boring ambrosia beetles spread Rapid ʽŌhiʽa Death - ROD - by releasing fungal spores from infected trees while digging reproductive passages. Our primary goals are to identify the community of beetles that attack ōhiʽa infected with ROD, the extent to which beetles may directly or indirectly spread the disease, understand the timing of beetle attack, and estimate how long infected trees remain a threat to spread the disease.
What is Rapid ʽŌhiʽa Death?
Rapid ʽŌhiʽa Death - ROD - is a devastating disease that afflicts ōhiʽa - 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 ōhiʽa, although C. lukuohia is more aggressive.
To better understand this threat, we are identifying the extent to which beetles and their frass or boring dust -macerated wood particles, dead beetle parts, and poop- can spread Ceratocystis, both locally and across the landscape. Furthermore, it’s unknown whether beetles’ interaction varies with C. lukuohia and C. huliohia. So, it’s important to investigate the interaction between beetles and their frass and each type of Ceratocystis independently.
Objectives:
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To understand prevalence of Ceratocystis, we are screening ambrosia beetles for Ceratocystis and culturing Ceratocystis spores recovered from beetles and boring dust. During this phase we will also estimate how long Ceratocystis spores remain viable under a variety of environmental conditions.
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To understand the dispersal of ROD, we are testing the extent C.lukuohia and C. huliohia travel by wind or flying beetles.
Accomplishments:
- We found viable Ceratocystis fungi associated with beetle frass in ōhiʽa logs. Of note, viable fungi are in frass along much of a tree.
- We observed by beetle trapping that the ambrosia beetle community consists of numerous species, including several known to attack ōhiʽa.
- We observed that adult ambrosia beetles can carry viable spores, and other forms of inoculum, on their bodies and that the beetles are capable or transferring the fungi to healthy ōhiʽa seedlings.
- Determined that ambrosia beetles attack infected ōhiʽa for at least 18 months after the time of tree inoculation.
Pathways for Movement and Rate of Spread of Rapid ‘Ōhi‘a Death on the Island of Hawai‘i
Wood-boring ambrosia beetles spread Rapid ʽŌhiʽa Death - ROD - by releasing fungal spores from infected trees while digging reproductive passages. Our primary goals are to identify the community of beetles that attack ōhiʽa infected with ROD, the extent to which beetles may directly or indirectly spread the disease, understand the timing of beetle attack, and estimate how long infected trees remain a threat to spread the disease.
What is Rapid ʽŌhiʽa Death?
Rapid ʽŌhiʽa Death - ROD - is a devastating disease that afflicts ōhiʽa - 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 ōhiʽa, although C. lukuohia is more aggressive.
To better understand this threat, we are identifying the extent to which beetles and their frass or boring dust -macerated wood particles, dead beetle parts, and poop- can spread Ceratocystis, both locally and across the landscape. Furthermore, it’s unknown whether beetles’ interaction varies with C. lukuohia and C. huliohia. So, it’s important to investigate the interaction between beetles and their frass and each type of Ceratocystis independently.
Objectives:
-
To understand prevalence of Ceratocystis, we are screening ambrosia beetles for Ceratocystis and culturing Ceratocystis spores recovered from beetles and boring dust. During this phase we will also estimate how long Ceratocystis spores remain viable under a variety of environmental conditions.
-
To understand the dispersal of ROD, we are testing the extent C.lukuohia and C. huliohia travel by wind or flying beetles.
Accomplishments:
- We found viable Ceratocystis fungi associated with beetle frass in ōhiʽa logs. Of note, viable fungi are in frass along much of a tree.
- We observed by beetle trapping that the ambrosia beetle community consists of numerous species, including several known to attack ōhiʽa.
- We observed that adult ambrosia beetles can carry viable spores, and other forms of inoculum, on their bodies and that the beetles are capable or transferring the fungi to healthy ōhiʽa seedlings.
- Determined that ambrosia beetles attack infected ōhiʽa for at least 18 months after the time of tree inoculation.