J. Y, Uchlda University of Hawaii, Honolulu

Members of the are ter- ported over 5.6 million Dendrohium Pyihiurn splendems H. Braun, Pythiurn restrial, epiphytic, or vinelike sprays from lareign countries (22). ulrimum Trow, Rhiroc~oniasolani distributed throughout the world in In Thaitand. the world's Largest pro- Kilhn. Sclerotium rovsii Sacc., Seploria temperate and tropical regions. Close to ducer of Dendrohium, the cultivar Sonia spp., Sphenospora kevorkianii Linder, 200 genera and hybrid genera are cul- accounts for over 70% of the Dendrobium and Uredo spp. (5). These organisms are tivated within the 600-800 genera esti- grown, whereas University of Hawaii cul- associated with blights, leaf rots mated for these strikingly unusual plants tivars dominate production in Hawaii. or spots, stem or pseudobulb rots, root (1 2). The estimated 3-year cost for a 1.5-acre rots, decline, and seedling The Orchidaceae is generally consid- farm in Hawaii {excluding land cost of damping-off. ered !o be the largest family of fl owering $30,000-$150,0001 acre) exceeds $200,000, Some of these pathogens have been plants in terms of the number of whereas a similar farm costs less than noted to occur in other parts of the world (1 2), with 17,000-30,000 species repre- $4,000 in Thailand (22). Hawaii's growers (It ,I 6). Geographic isolation and state senting n highly diverse group. Common receive higher wholesale prices for agricultural quarantine reguiations have commercially cultivated genera include products of 'better quality than those prevented the establishment of rusts in terrestriat Paphiopedilurn and Phaius from competing nations (22). Hawaii, but all other fungal pathogens and epiphytic Brasrovolo, Corrleya, The climate range in Hawaii is con- listed above are now known to occur in Coelogytte. Cvmhidium. Dendrohium. ducive to the growth of many orchid Hawaii. , Laefia. Lycos~~.Milronia. genera, allowing for large collections The rapid growth of the orchid Odontaglos.sum, Oncidiurn, Phalaenop- among hobbyists and stimulating com- industry in Hawaii during the 1980s was sis. Vanda, and Vanilla. Hobbyists fre- mercial production. Several commercial accompanied by a proliferation of quently collect Aprides, Falanrhe. orchid nurseries in Hawaii breed and diseases with unknown etiologies. Little Catas~rurn, and MoxiElaria. propagate a wide variety of species and research-based information was avail- Orchids are propagated by seed, vege- hybrids. Plants are sold locally to other able for the many pathogens associated tative division, or mericloning. Seed and nurseries or hobbyists and also are ex- with diseases of orchids. Our research rnericlone propagation both require ported nationally or internationally. efforts were focused on diseases of months of axenic agar culture but yield Orchid plants are sold in axenic flask D~ndrohium,with support for studies thousands of new plants. Those propa- culture, in multiplant community pots, coming from commercial growers and gated by seed have considerable genetic as individual young plants, or as mature slate agencies, and findings have aided diversity, whereas those propagated by plants with flower buds. A tremendous local and international growers. These mericloning have almost none. number of genera are grown in the state, studies atso serve as a foundation for The commercial value of various including a number of species that thrive investigations of problems in other orchid crops in Hawaii approximated in cooler areas, For example, cultivars of genera, such as Catrleyo. Cymbidium, $I I million in I990 (2). Included were Cymbidium, Dendrobium, and Phalae- Epidendrum, and Vanda. This article sales of detached Vanda, Carllqva, and nopsis. Over 100 nurseries in Hawaii describes important diseases of orchids D~ndrobiumblossoms, Cymbidium and produce orchids. with many specializing in Hawaii, with emphasis on fungal Dendrohium sprays, and potted plants in selected genera of potted plants or in diseases associated with Dendrobium. of many genera. In 1989, Thailand flower production (E). exported approximately 300 million In the Un~tedStates, fungal pathogens sprays of Dendrohium and frequently associated with common Botrytls Blossom Bllght also exported a large number of sprays, orchid genera. include: Aecidium Bosrytis cinereo causes floral spots, with about one-half of the exports from graehnerianum Renn., Allernaria spp., petal blights, and soft rots of many plant both going to Japan. In 1989. Hawaii Bipolaris spp., Borryti~cinerea Pers.: Fr., genera. In 1952, blossom rot of Vonda exported nearly 3.2 million sprays, Cercospora spp., Colleiotrichum gloeo- occurring in shipments to the continental mostly to the U.S. mainland, which im- sporioides (Penz.) Penz. & Sacc. in United Stares was attributed to unidenti- Penz., Fusarium oxysporum Schlech- fied species of Botrytis. Gloeosporiurn, tend.:f s., Lasiodiplodia rheobromae and Airernaria (6). Today,most cornmer- (Pat.) Griffon & Maubl., Phoma spp., cia1 cultivars of Dendrobium and Vanda Dr. UchidaP address is: Plant Pathology Depart- PhyElost lcta capiralensis Henn., Phy- are known to be susceptible to 8. cinerea, mtnt. University of Hawaii. 31W Mailc Way. rophrhora cactorum (Cebert & Cohn) J. whereas from Catileya, Cymbidium, Honolulu. HI 96822. SchrGt.. Phyfophthora palmivora (E.J. Epidendrum, and Pholaenopsis are more Butler) E.J. Butler, Pseudocercospora tolerant of this fungus. Flower blights e- 1994The American Phytopathological SociaFj spp., Pcrccinia cypripedii Arth. & Holw., on Dendmbiurn begin as small flecks or 220 Plant DiseaseNol. 78 No. 3