Plant Disease July 2008 PD-42 Cassytha filiformis Scot C. Nelson Department of Plant and Environmental Protection Sciences assytha filiformis is, depending on one’s perspective, Hosts Ca blessing or a bane. It is a C. filiformis parasitizes a wide variety of mainly woody • plant treasured by Hawaiians for its traditional use as hosts, including plants of agricultural and economic a light-hearted or ceremonial human ornament and in value, and indigenous as well as and endemic species. decorative garlands and lei Among the important economic hosts are fruit plants • valued plant in traditional societies with diverse such as citrus, mango (Mangifera indica), cloves (Eu- healing applications and with promise for modern genia aromatica), nutmeg (Myristica fragrans), and medicine avocado (Persea americana). It also is frequently found • food plant for humans and animals on many other endemic tropical and subtropical species • vine used in thatched roof construction worldwide. In Hawai‘i, it commonly occurs on native or • potential biological control agent for invasive plants naturalized woody coastal hosts such as Tournefortia • pestiferous and pathogenic weed that is a threat to argentea (tree heliotrope), Scaevola sericea (beach nau- agriculture and endangered plants and is capable of paka), Metrosideros polymorpha (‘ōhi‘a lehua), Morinda transmitting other pathogens between plants. citrifolia (noni), Pandanus sp. (screw pine) and on plants surrounding these hosts, including a wide range of Cassytha filiformis L. is a leafless, climbing, twining, shrubs and herbaceous succulents, weeds, grasses, and vine-like, autoparasitic and plant-hyperparasitic phanero- groundcovers. According to Nickrent (2002), C. filifor- gam (seed-bearing plant) in the plant family Lauraceae. mis “appears to be totally indiscriminate in host choice, It infests a wide variety of coastal plants throughout often covering and parasitizing dozens of host species Hawai‘i, the Pacific, and the tropics worldwide. Indig- simultaneously.” enous to Hawai‘i, it is one of many higher flowering plant species that have, through evolutionary divergence, Genus Cassytha become parasitic on various organs of other higher plants. Cassytha is a genus of about 20 species, most occurring Having long ago lost certain metabolic processes and in Australia, a few in South Africa, and one pantropical physical structures to support it and remain indepen- species (C. filiformis). The genus name derives from dent, C. filiformis clings to other, mainly woody, plants kesatha, Aramaic for “a tangled wisp of hair.” Cassytha for physical support, nutrition, and water. Its common species are parasitic vines with small haustoria (infec- names are kauna‘oa pehu, kauna‘oa malo-lo, kauna‘oa tious, adhesive structures used to withdraw nutrients from uka, kauna‘oa, malolo, pololo (in Hawaiian), dodder host organs through host cell membranes). Its stems are laurel (or laurel dodder), woe vine, and love vine. This filiform, containing chlorophyll. The leaves are reduced species was formerly named Cassytha senegalensis A. to minute scales. The flowers are sessile or pedicellate, Chev. and Cassytha guineensis Schumach. & Thonn. in heads or spicate or racemose inflorescences; the flo- Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in coopera- tion with the U.S. Department of Agriculture. Andrew G. Hashimoto, Director/Dean, Cooperative Extension Service/CTAHR, University of Hawai‘i at Mänoa, Honolulu, Hawai‘i 96822. An equal opportunity/affirmative action institution providing programs and services to the people of Hawai‘i without regard to race, sex, age, religion, color, national origin, ancestry, dis- ability, marital status, arrest and court record, sexual orientation, or status as a covered veteran. CTAHR publications can be found on the Web site <http://www.ctahr.hawaii.edu/freepubs>. UH–CTAHR Cassytha filiformis PD-42 — July 2008 ral tubes are shallow, enveloping the fruit; there are six persistent tepals, the outer three smaller than the inner three, nine fertile stamens, those of the third whorl with two basal glands, the fourth whorl reduced to staminodia; the anthers are dithecal. The fruit is enclosed in the floral tube with a persistent perianth. Description of Cassytha filiformis Stems are green to orange, filiform, and glabrous. Leaves are reduced to minute scales, ca. 1 mm long, easiest seen near tips of stems. Flowers are sessile and few in spicate inflorescences 1(–2) cm long, each one subtended by an ovate bract and two ovate bracteoles, those with ciliolate tips; tepals are glabrous, strongly unequal, outer three ovate, ca. 1 mm long, inner three elliptic, ca. 2.5 mm long, their tips incurved; the fertile stamens are glabrous, outer 6 introrse, broad, with very short filaments acute apex, inner three extrorse, with two sessile glands at base, the tip elongated beyond anther cells into a slender beak, the fourth whorl of stamens reduced to glabrous staminoda; the ovary is globose, glabrous. Fruits are enclosed in the accrescent floral tube; dried floral parts persist in the fruiting stage. Similar plant species Cassytha filiformis on Metrosideros polymorpha (‘ōhi‘a) Two plant-parasitic phanerogams in Hawai‘i (two Cus- on the South Kona coast, island of Hawai‘i cuta species of the family Convolvulaceae, the dodders) have a similar appearance to C. filiformis and a similar mode of parasitism. The most readily visible features that distinguish these two genera (Cassytha vs. Cuscuta) appear in the inflorescence and the fruits (Table 1). The flowers of cuscuta are small, about 2 mm in diam- eter, and are borne singly along the stem. The fruit is a dry, spherical, thin-shelled structure containing several small black seeds. The flowers ofC. filiformis are borne in small panicles. The fruit is small, fleshy, and berry-like, bearing a single, spherical seed. Cuscuta species are annuals, whereas C. filiformis is a perennial. C. filiformis parasitizes mainly woody plants, whereas with the exception of Cuscuta exaltata (not reported in Hawai‘i), dodders usually parasitize Cassytha filiformis on noni (Morinda citrifolia), in the herbaceous plants. coastal Puna district, island of Hawai‘i The two Cuscuta species in Hawai‘i and C. filiformis are sometimes confused. In fact, they are all nowadays Photos: Unless noted otherwise, photos are by S. Nelson. sometimes referred to by the same name in the Hawai- ian language, kauna‘oa. This fact calls into question the accuracy some of the reported host ranges found in the 2 UH–CTAHR Cassytha filiformis PD-42 — July 2008 Table 1. Comparison of distinguishing features for Cassytha filiformis and two Cuscuta species in Hawai‘i. Cassytha (love vine) Cuscuta (dodder) Family Lauraceae Convolvulaceae Stems Green to orange Pale yellow (C. campestris), or yellow to yellowish orange (C. sandwichiana) Flowers Spicate inflorescence Globose clusters (C. campestris), (similar to a raceme) or cymose clusters (C. sandwichiana) Growth habit Climbing, spreading Mainly spreading across groundcovers Host preference Virtually indiscriminate, tending in Generally herbaceous plants. Hawai‘i to infest woody plants C. campestris favors legumes, whereas (trees and shrubs), but also a parasite C. sandwichiana is not as host-specific of a wide range of herbaceous hosts Flowers of Cassytha species (also known as “dodder Flowers of Cuscuta species (dodders) occur in cymose laurels”) occur in spicate or racemose clusters; these to globose clusters; these plants tend to spread across plants tend to climb up and parasitize larger woody and parasitize herbaceous plants at ground level. plants and shrubs. (Photo: UH-CTAHR, Growing Plants for Hawaiian Lei) published literature. In Hawai‘i, the three similar para- ous plateau and coastal woodlands, montane grasslands sitic seed plant species are C. filiformis (indigenous), and dambo margins, and vegetation of sandy beaches or Cuscuta sandwichiana (endemic), and Cuscuta camp- lakes. It grows on small bushes, woody shrubs and low estris (introduced) (Table 1). trees, grasses, and herbaceous weeds. C. filiformis has pantropical distribution throughout Seeds may be spread by animals, water, strong winds, coastal areas; in Hawaii, it has been reported on a variety farm machinery or with crop seed. The plant may spread of hosts, usually growing in coastal habitats, and docu- locally by vegetative growth between hosts and over soils. mented from all the major islands except Kaho‘olawe. Examples of its dispersal include: In Hawai‘i, C. filiformis is indigenous. On Kure Atoll, • Seeds are carried by ocean currents among and be- (Northwestern Hawaiian Islands), a small patch was tween continents and islands, or locally by streams or found in recent years on the northeastern coast as a rivers, or seasonally flowing water. parasite of Scaevola sericea (beach naupaka). • Seeds are consumed and dispersed by some birds. It inhabits coastal vegetation, usually on sandy dunes, • Seeds are dispersed by strong winds (hurricanes/ty- margins of evergreen gully and riverine forests, decidu- phoons). 3 UH–CTAHR Cassytha filiformis PD-42 — July 2008 Cuscuta campestris on the legume white clover (Trifolium repens); both species are introduced to Hawai‘i. • Seeds are consumed and dispersed in Australia by macropods (e.g., the Rufus Hare wallaby, Lago- rchestes hirsutus). • Seeds can contaminate the seed lots of other plant species and be planted