{"id":11549,"date":"2019-06-30T02:03:49","date_gmt":"2019-06-30T02:03:49","guid":{"rendered":"https:\/\/environment-hawaii.org\/?p=11549"},"modified":"2019-06-30T18:49:27","modified_gmt":"2019-06-30T18:49:27","slug":"scientists-resource-managers-seek-to-understand-halt-spread-of-rod-2","status":"publish","type":"post","link":"https:\/\/environment-hawaii.org\/?p=11549","title":{"rendered":"Scientists, Resource Managers Seek To Understand, Halt Spread of ROD"},"content":{"rendered":"\n
\"\"
In the Agricultural Research Service lab in Hilo, sections of `ohi`a trunks infected with the Ceratocystis fungus are placed in fabric cages to see what insects emerge from them. Credit: J.B. Friday<\/figcaption><\/figure>\n\n\n\n

So you want to stop rapid \u2018ohi\u2018a death in its tracks? <\/p>\n\n\n\n

Probably the very best thing you can do\nis to remove goats, pigs, cows, deer, and\nsheep from the area you want to protect \u2013\nand fence that land to keep them out.\n<\/p>\n\n\n\n

At a two-day scientific symposium held in late May, dozens of experts who have been studying the disease that threatens hundreds of thousands of acres of Hawaiian forests came together to discuss all that they have learned in the four years since the disease was given a name. <\/p>\n\n\n\n

Many of the practices that have been\nrecommended to prevent the spread of\nthe two fungi that cause the \u2018ohi\u2018a to die\nare all-round sensible hygiene, good to\ndo regardless of what impact they might\nhave in curbing the spread of rapid \u2018ohi\u2018a\ndeath. Yes, clean boots before going on\nthat trail. Do hose off trucks and scrub\nother equipment before moving them from\none forested area to another. By all means,\ndon\u2019t mark trails or other landmarks into\ntrees with your hatchets. Never take any\npart of an \u2018ohi\u2018a tree \u2013 flowers, stems, wood,\nwhatever \u2013 from one island to another\nwithout clearing it with state agricultural\ninspectors.\n<\/p>\n\n\n\n

But their utility in stopping the spread\nof rapid \u2018ohi\u2018a death isn\u2019t entirely clear.\n<\/p>\n\n\n\n

What is clear is the important role\nfences play \u2013 not that they keep out the\nfungi that cause ROD, but that they keep\nout the animals that wound the trees,\nthereby opening pathways for the airborne\nspores of the fungi to invade otherwise\nhealthy trees.\n<\/p>\n\n\n\n

Some of the most dramatic slides presented at the symposium were aerial shots that showed fenced areas immediately adjacent to unfenced ones, with dead \u2018ohi\u2018a highlighted. Inside the fenced areas, there may have been a few infected trees, but nowhere near the numbers seen in the forests outside the fence. As Flint Hughes, of the U.S. Forest Services Institute of Pacific Islands Forestry put it, describing one such area in the Big Island district of Ka\u2018u, \u201ca huge blob of death\u201d was seen outside the fenced area, while inside, \u201cwe have yet to find a [ROD-]positive tree.\u201d <\/p>\n\n\n\n

WUD and ROD\n<\/strong><\/p>\n\n\n\n

Driving home the same point was the\npresentation of Emma Yuen, native\necosystems protection and management\nmanager at the state Department of Land\nand Natural Resources.\n<\/p>\n\n\n\n

Yuen linked rapid \u2018ohi\u2018a death to an\neven older and more widespread problem\nshe called WUD, or widespread ungulate\ndamage.\n<\/p>\n\n\n\n

\u201cWe have millions of trees that have died because of WUD for more than two centuries now. More than 100 studies have been done showing how damaging WUD\nis in over two million acres of \u2018ohi\u2018a and\nother native forests,\u201d she said. Today, even\nthough on the Big Island, 160,000 acres\nare free of hoofed animals, that number is\ndwarfed by the more than 2 million acres\nthat are still unfenced, she added.\n<\/p>\n\n\n\n

Now the DLNR is attempting to have\nsome of the funds allocated to fight rapid\n\u2018ohi\u2018a death used to fence and remove\nungulates from forested areas.\n<\/p>\n\n\n\n

Despite the clear link between WUD and ROD, Yuen said, there\u2019s a need to be strategic in identifying areas that should be prioritized for fencing. Also, given the objections that Hawai\u2018i\u2019s vocal community of hunters is likely to raise against additional fencing, Yuen asked how it might be possible \u201cto translate the community\u2019s \u2018ohi\u2018a love into support for actions needed to protect forests?\u201d <\/p>\n\n\n\n

Finally, she threw down a challenge to\nthe state\u2019s conservation community to use\nthe data on the link between ungulates and\nrapid \u2018ohi\u2018a death \u201cto fence and protect\nareas with a renewed urgency.\u201d\n<\/p>\n\n\n\n

In the Air\n<\/strong><\/p>\n\n\n\n

The two different species of Ceratocystis <\/em>implicated in ROD result in the same event \u2013 the death of the tree \u2013 but by different mechanisms and over different time spans. C. lukuohia <\/em>causes death by quickly spreading through the tree\u2019s vascular system, while C. huliohia <\/em>is slower, causing cankers to form inside the tree. Death is almost certain, but it may take months or even longer. <\/p>\n\n\n\n

Thomas Harrington, a professor at\nIowa State University who has extensively\nstudied fungal diseases of trees, described\nthe different ways in which he suspects\nthe fungi are spread. C. lukuohia<\/em>, he said,\nwas most associated with wind, while C.\nhuliohia <\/em>is found in trees that are more\nprotected.\n<\/p>\n\n\n\n

To support the notion that the more devastating fungus is carried by wind and not, for example, by insects, Harrington showed two aerial photos of the same area, Wao Kele o Puna, before and after Hurricane Iselle, which hit Puna in August 2014. <\/p>\n\n\n\n

In 2008, there\u2019s no sign of any diseased trees, but 18 months after Iselle, \u201cthe forest is transformed.\u201d <\/p>\n\n\n\n

Near Hakalau Forest National Wildlife Refuge, C. lukuohia <\/em>hit an area that, Harrington said, is undisturbed and has no ambrosia beetles, a type of insect that\u2019s suspected of carrying spores of the fungus from infected trees to uninfected ones, thereby spreading the disease. This, he said, \u201ccould not be human-associated inoculation. It had to be the wind.\u201d <\/p>\n\n\n\n

Genetic analysis of the C. lukuohia\n<\/em>found in infected Kaua\u2018i trees showed\nit to be close to strains found on the Big\nIsland and is very likely to have come\nfrom there, \u201cprobably in a wind event,\u201d\nHarrington said.\n<\/p>\n\n\n\n

\u201cTrees that are exposed to the wind,\ntrees above the canopy, seem to be the\nmost susceptible\u201d to infection with this\nspecies, he said.\n<\/p>\n\n\n\n

Why are those taller trees more likely\nto be infected with C. lukuohia?\n<\/em><\/p>\n\n\n\n

Harrington has a theory. \u201cI suspect\nit\u2019s because of the upright architecture of\nthe tree. In between the stems that grow\ntogether is old bark. In the wind, they\u2019ll\nopen up the tree where the included bark\nis,\u201d he said. \u201cThe heaviest stain\u201d \u2013 which\nis symptomatic of infection by C. lukuohia\n<\/em>\u2013 \u201cis often in the included bark.\u201d\n<\/p>\n\n\n\n

Wade Heller, with the U.S. Department of Agriculture\u2019s Pacific Basin Agricultural Research Center in Hilo, noted that air samples from more than 20 sites had tested positive for either or both species of fungus as far as 20 miles from the closest known infected tree. DNA was present in trace amounts \u2013 although he cautioned that the mere presence of DNA did not indicate that the fungus was viable. <\/p>\n\n\n\n

Sheri Mann, Kaua\u2018i manager for the\nstate Division of Forestry and Wildlife,\nsaid she, too, suspects that wind has been\na big factor in the spread of Ceratocystis\n<\/em>on that island, where both species have\nbeen found.\n<\/p>\n\n\n\n

Are Beetles to Blame?\n<\/strong><\/p>\n\n\n\n

Ambrosia beetles, sometimes called \u201cfungus farmers,\u201d have also come under suspicion as a means of infection. Kylle Roy and Kelly Jaenecke, researchers with the U.S. Geological Survey\u2019s Pacific Island Ecosystem Research Center, described the research they had done on the possibility that the beetles\u2019 frass \u2013 the sawdust-like waste the beetles produce \u2013 might carry the fungus from one tree to another.<\/p>\n\n\n\n

Less than 10 percent of the frass samples\nthey collected contained Ceratocystis\n<\/em>DNA, but no spores were detected.\n<\/p>\n\n\n\n

The beetles themselves may be able to\ncarry the fungus from one tree to another.\nRoy and Jaenecke are just starting to test\nthis possibility.\n<\/p>\n\n\n\n

Franny Brewer, communication director with the Big Island Invasive Species Committee, reported on a study she conducted last year at trailheads on the Big Island that revealed the presence of Ceratocystis <\/em>DNA in dirt. <\/p>\n\n\n\n

She and co-workers collected dirt from\nboot brushes and nearby areas, tested that\nfor the presence of Ceratocystis <\/em>DNA, and\nthen attempted to grow it out on carrots,\nthe culture medium used most frequently\nto determine fungal viability.\n<\/p>\n\n\n\n

Trace amounts of DNA from both species were present in every sample, although most of it was not able to be cultured. <\/p>\n\n\n\n

\u201cThe surprising thing is where we actually were able to culture Ceratocystis <\/em>from samples \u2013 neither of them came from places where there\u2019s a lot of ROD-infected trees nearby,\u201d she said, adding that the inoculum probably came from far away on someone\u2019s boot. <\/p>\n\n\n\n

Brewer added that she had tested a\nlimited number of samples from off-\nisland. \u201cAll have been negative so far,\u201d\nshe reported.\n<\/p>\n\n\n\n

Harrington spelled out what he sees as the long-term future of Hawai\u2018i forests: \u201cThere\u2019s DNA floating around everywhere, just looking for a wound. I think it\u2019s eventually going to spread through all \u2018ohi\u2018a forests on the Big Island, although the percentage of trees dying is actually small.\u201d <\/p>\n\n\n\n

He defined success as \u201ca low level of\ninfected trees. You\u2019re not going to get rid\nof it on the Big Island.\u201d\n<\/p>\n\n\n\n

Eventually, he added, \u201cit may take\ndecades, but the fungus will be in \u2018ohi\u2018a\nforests all around the islands. Maybe five to\nten percent may go out over a decade.\u201d\n<\/p>\n\n\n\n

One positive aspect: \u201cIt doesn\u2019t spread rapidly from one tree to the next. That\u2019s what is different about this disease as opposed to, for example, chestnut blight or oak wilt. … We\u2019re not seeing it wipe out the whole forest. I\u2019m more hopeful than most, but I think we have to accept some level of disease.\u201d <\/p>\n\n\n\n

\u2014 Patricia Tummons <\/strong><\/p>\n\n\n\n

Donate<\/a><\/div>\n","protected":false},"excerpt":{"rendered":"

So you want to stop rapid ‘ohi‘a death in its tracks? Probably the very best thing you can do is to remove goats, pigs, cows, deer, and sheep from the area you want to protect – and fence that land … Continued<\/a><\/p>\n","protected":false},"author":1,"featured_media":11547,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[15,25,455],"tags":[7],"class_list":["post-11549","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-forests","category-invasives","category-july-2019","tag-patricia-tummons"],"_links":{"self":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/posts\/11549","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=11549"}],"version-history":[{"count":0,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/posts\/11549\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/media\/11547"}],"wp:attachment":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=11549"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=11549"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=11549"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}