Decline of Ohia Lehua Forests in Hawaii
Decline of Ohia Lehua Forests in Hawaii
Decline of Ohia Lehua Forests in Hawaii
Decline of Ohia Lehua Forests in Hawaii

Decline of Ohia Lehua Forests in Hawaii

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    est and Rangeeriment St ationSERVICEMENT OF AGRICULTUREBOX 245, BERKELEY, CALIFORNIA 94701

    USDA FOREST SERVICEGENERAL TECHNICALR EPOR T PSW - 3 I1972

    DECLINE OF OHIA LEHUA FORESTSI N H A W A I I

    Robert E. Burgan Robert E. Nel sonOn the island of Hawaii, thousands of acres of ohia lehua

    (Metrosideros collinu) forests have died, and tree death is pro-gressing rapidly into healthy forests. Ohia trees are the chief vic-tims, but koa (Acacia koa) trees are also dying. Covering some600,000 acres on t he island o f Hawaii, ohia a nd koa forests pro-vide a variety of resource values-watershed cover, wildlife habi-tat, timber, forage, and recreation. Some parts are still relativelyundisturbed and, therefore, are of special significance for scien-tific study . Fu rtherm ore, these forests are unique, having evolvedin isolation fr om o the r forests. Ways to prevent an epidemic situa-tion from spreading further must be given intensive and immedi-ate study. Unless a remedy can be found, ohia forests as knowntoday may become relicts.

    Most of the affected area is on State-owned land, but signifi-cant acreage of National Park and private lands are also included.The decline of the ohia forests is of concern to a number ofagencies:The C ounty of Hawaii Departm ent o f Water Supply is con-cerned tha t o ne result may be a decline in the quality or quantityof water flowing from mo untain watersheds.The Volcanoes National Park has reported that most of a9,000-acre section of the Upper Olaa Forest Reserve is affected.This Reserve was set aside in 1951 because it was such a goodexample of the original forest and vegetation type on the island.The U.S. Fish and Wildlife Service has noted that withinthe National Park, bo th the num ber of bird species and total birdpopulations are rapidly declining in areas where the ohia foresthas died, in contrast to n o change or grow th in populations wherethe trees are still healthy.

    Burgan, Robert E. , and Robert E. Nelson1972. Decline of ohia lehua forests in Hawaii. Pacific SouthwestForest and Range Exp. Stn., Berkeley, Calif. 4 p.. illus. (USDAForest Sew. Gen. Tech. Rep. PSW-3)Thousands of acres of ohia lehua (Metrosidems collina) forests on theisland of Hawaii have died, and tree death is progressing rapidly intohealthy forests. Most of the losses are on State-owned lands. All of the"ohia decline" cannot be attribut ed t o the same agent. Sonie of the earlierdecline was attributed to frost and sulphur dioxide. But other factors.including possibly the shoestring root-rot (Armillaria mellea), are respon-sible for the current losses. Federal and State agencies iire seeking to determine the causes of the decline and what control measures are feasible.Oxford: 48(969) [+ 176.1Metrosideros collina + 176.1Acacia koa + 172.8Armillaria mellea] .Retrieval Terms: Hawaii; ohia decline; forest diseases; epidemics; Acaciakoa: Metrosideros collina; Armillaria m ellea.

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    The ohia forest at the right appearshealthy compared to that at the left.Whether the "disease front" is movinginto the healthy forest is not know n.

    The U.S. Forest Service and Hawaii Division ofForestry estimate that the ohia and koa forests hold atotal volume of about 470 million board feet of tim-ber. At a stumpage value of only $ 10 per 1,000 boardfeet, for example, this resource would be worthnearly $5 million o n the stump-a base for some $125million worth of consumer products. Probably 10percent of the timber has already been killed in theepidemic.

    "OHIA DECLINE"Published reports of the decline of ohia forestsdate from 1909, when L yon (1909) told about

    forests dying on windward Maui. Clifton J . Davis,Entomology Branch Chief, Hawaii Department ofAgriculture, referred to the "Ohia Lehua Dieback"

    near Pauahi and Hiiaka Craters in a 1 946 report a bou tinsect cond itions in Hawaii National Park.' But onl yrecently has the "ohia decline" on th e island ofHawaii reached epide mic proportions.All of the "ohia decline" cannot be attributed tothe same agent. Several small pockets of ohia above4,000 feet elevation have been either damaged orkilled dow n to ground line b y frost. In areas nearvolcanoes, some trees have been injured by po isonousfumes, chiefly sulphur dioxide. Most of the current

    loss, however, is not likely due to either frost or sul-phur dioxide.SHOESTRING ROOT-ROT

    An apparent contributing factor is shoestring root-rot (Armillaria mellea). This root-destroying fungushas been isolated from affected trees in areas of seri-ous decline where sulphur dioxide and frost are defi-, nitely not involved. The fungus was first reported at-tacking forest trees in Hawaii by Robert V. Bega, ofthe U.S. Forest Service, who discovered it o n silk-oak(Grevillea robusta) in 1962. It was subsequently

    found o n ko a and ohia by Raabe in 1963 (Raabe andTrujullo 1963).Since t hen the fungus has been observed by ot her son these same species. It has also been found o n hau-kuahiwi (Hibiscadelphus hualalaiensis), naio (Myo-porum sandwicense), olupua (Osmanthus sandwicen-sis), kopiko (Straussia sp.), manono (Gouldia spp.),pi10 (Coprosma spp .), kolea (Myrsine spp.), mama ki(Pipturus alb idus), a'e (Zanthoxylum dipetalum),pukiawe (Styphelia tameiameiae), and mamani(Sophora chrysophylla).Armillaria mellea may have been introduced intothe Hawaiian Islands on fruit tree nursery stock dur-ing the early 1900's. Its subsequent spread could havebeen accelerated by the high populations of intro-duced ra ts and wild pigs.This fungu s is propagated in tw o ways: Its basidio-spores are wind-borne and can establish themselves inold stumps or dead trees, but cannot infect healthy' ~ o t e s n Forest Insect Cond itions, Hawaii National Park forthe year 1946. January 6 , 194 6. (Memorandum on tile at theInstitute of Pacific Islands Forestry, H onolulu, H awaii.)2~o mm uni cati on ith Franklin Laemmlen, Plant Pathologist,University of Hawaii, and observations of the U.S. ForestService and Hawaii Division of Forestry Surve y Team.

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    trees. Healthy trees are infected by the brown orblack cordlike rhizomorphs or "shoestrings" whichgrow out from infected roots. On meeting a healthyroot, the rhizomorph penetrates it and grows up thecambial layer to the roo t crow n, which it girdles. Theleaves become dwarfed, turn yellow or fall prema-turely; on small trees all foliage may die simultane-ously.

    This heavily diseased port ion of a n ohiaforest is typica l o f thousands of acres offorest decline on the island o f Haw aii.

    Only the skeletal stems of trees remainin what was once a luxuriant ohia rainforest on th e island of Hawaii.

    The parent lava type, soil struc ture, moisturestresses, insects, and other ecological factors may alsobe involved in the decline.

    HILO FOREST RESERVEThe condition of the ohia forest within the b ound-

    aries of the 120,000-acre Hilo Fores t Reserve, hasbeen evaluated on a sampling basis from black and

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    white aerial photo graph s taken in 1 95 4 and 1 965. and U.S. National Park Service have joined forces inThe area in each of fou r cond ition classes was esti- seeking answers to .such questions as: What is themated . The fou r classes were: (1) healthy forest-no present location, extent, and rate of spread of thetrees dead ; (2) slight decline-less than 20 percent of epidemic? What are the subsequent effects on thetrees dead; (3) moderate decline-20 to 60 percent of composition of the forests? What are the major causesthe trees dead; (4) severe decline-gore than 6 0 per- of death of the ohia and koa trees? What are thecent of the trees dead. factors (host-pathogen-environment complexes) con-

    The area of healthy forest decreased from 53,000 tributing to the recent acceleration of this decline?acres in 1954 to 43,00 0 acres in 1965. The acreage of Can feasible control measures be .developed and ifslight and mod erate decline remained ab out t he same. not, what are the alternatives? Deciding on alternatesBut the area of severe decline nearly tripled-from if practical control measures are not possible may5,000 acres in 195 4 to 14,000 acres in 1965. well be the most challenging task in this coordinatedObservations indicate that the present decline con- effort .dition is even more serious. Large areas of forests LITERATURE CITEDobserved as healthy in 1967 are now heavily affectedas the decline has spread rapidly south from the Lyon, Harold L.Saddle Road. 1909. Th e forest disease o n Maui. Hawaiian Planters'~ e c o r d1 :92-95;15 1-159 .What can be done about this situation? The U.S. Raabe, R. D., and E.E. Trujillo.Forest Service, Hawaii Division of Forestry, Univer- 1963. Armillaria mellea in Hawaii. Plant Disease Rep.sity of Hawaii, Hawaii Department of Agriculture, 47: 776.

    The AuthorsROBERT E. BURGAN is working o n forest gro wth and yield studies, withheadq uarters at th e Station's Institute of Pacific Islands Forestry , Hono-lulu, Hawaii. From 1963 t o 1969, he served on th e timber sales staff of th eUnion and later Bear-Sleds Ranger Districts, in Oregon. He earned bache-lor's and master's degrees in forestry at the University of Montana.ROBERT E. NELSON heads the Station's Institute of Pacific IslandsForestry , headquartered in Ho nolulu, Hawaii. He joined th e Forest Servicein 1941, after earning a forestry degree at the University of California. Hebecame field supervisor of th e California State Cooperative Soil-VegetationSurvey in 1949. Since 1957, he has been in charge of the Station's Hawaiioffice.

    U S. Forest Service research in Hawaiiis conducted in cooperation withDivision of Fo restryHawaii Department