Crassocephalum crepidioides
(redflower ragleaf)

C. crepidiodes is an invasive herb included in the Global Compendium of Weeds and classified as one of the most aggressive weeds occurring in tropical and subtropical regions (Randall, 2012). It is a pioneer species with the capability to produce large amounts of hairy wind-dispersed seeds. However, Chen et al. (2009) suggest that seed dispersal ability is limited. Chen et al. (2009) report that the species has only a moderate invasive capacity and that its wide distribution in China possibly correlates with its cultivation.

C. crepidioides is native to tropical Africa. It has become widely distributed eastwards out of Africa and Madagascar into the East Indies, India, South-East Asia and the Philippines, and it is still actively spreading, with a first record as a weed in Peninsular Malaysia published in 2009 (Kiew, 2009). It was first recorded in the Ryukyu Archipelago (Japan) in 1955 (Belcher, 1955).

Because this weed is often confused with Erechtites valerianaefolia, the full extent of its spread into the Orient may not be appreciated.

C. crepidioides is found mainly in the humid tropics at altitudes from 15-200 m up to 2500 m above sea level. It invades bare areas but disappears under shaded conditions. Soerjani et al. (1987) list it from arable land, by rivers and roadsides, on tea and chinchoma plantations, particularly in wet localities, and in upland ricefields. It occurs in newly opened or existing shifting cultivation fields, open areas of upland fields, waste places, orchards, coffee plantations, and newly sown pastures (Tjitrosoedirdjo, 1991).

C. crepidioides may be found infesting young tea plantations (Sastroutomo and Pandegirot, 1988), in rice, taro, coffee, citrus, sweet potatoes, vegetable crops, orchards and pastures.

The chromosome number in C. crepidiodes is 2n = 40 (Henderson, 1973; Vanijajiva and Kadereit, 2009). Hybrids with C. rubens have been recorded in north Thailand (Vanijajiva and Kadereit, 2009).

C. crepidioides is an annual weed that flowers all year round with a high seed production capacity. It is able to produce 29 flowers with approximately 4379 seeds per plant, reaching a plant density of 70.5 individuals per square metre in tea plantations. The seeds have a pappus of 10-11 mm and are therefore easily blown by wind soon after they have become detached from the mature inflorescence. The many seeds that are produced are thus spread rapidly.

Sauerborn and Koch (1988) found that C. crepidioides germinated at temperatures between 10 and 40°C: the lower limit of germination temperature explains the incidence at high altitudes. Nakamura and Hossain (2009) report a germination range of 10-30°C, with an optimum of 15-20°C. Seeds germinate over a wide pH range (2-12), with the highest germination rate at between pH 4 and 10. Germination rate was drastically reduced after one year, and emergence is high on the soil surface while no seedlings emerged from a depth of over 1 cm (Nakamura and Hossainm 2009). Chen et al. (2009) report that seeds have no apparent dormancy and retain high viability after room storage for 10 months.

Apety (1994) noted the action of a beetle Neolamprina (=Lamprina) sp. in Papua New Guinea. This weed is also attacked by Pseudomonas solanacearum in Australia (Pegg and Moffett, 1971).

Yogesh Kumar et al. (2011) report vein yellowing disease on C. crepidiodes growing as a weed in subtemperate northern India. The disease was associated with Ageratum enation virus (AEV), along with a nanovirus like satellite DNA 1.

Animal feed, fodder, forage

• Fodder/animal feed

Human food and beverage

• Flour/starch
• Leaves (for beverage)
• Vegetable

Medicinal, pharmaceutical

• Traditional/folklore

In parts of Asia where both species have been introduced, there has been frequent confusion between C. crepidioides and Erechtites valerianaefolia, of American origin. Tjitrosoedirdjo (1987) provides useful guidance to their separation. The leaves of C. crepidioides are lobed at the base but the upper half of the leaf is undivided whereas those of E. valerianaefolia are deeply and regularly pinnatifid for most of their length. In C. crepidioides the involucral bracts are green and brown (versus green only), the flowers yellow to reddish brown (versus yellow to reddish violet), achenes 2 mm long (versus 3 mm) and pappus white (versus reddish violet in the upper half). C. crepidioides rarely exceeds 1 m high (versus up to 2 m).

There can also be confusion with other Crassocephalum species.

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Manual Control

C. crepidioides may be found infesting young tea plantations (Sastroutomo and Pandegirot, 1988), where it is usually associated with relatively wide open spaces between young trees, growing together with other annual weeds such as Ageratum conyzoides and Galinsoga parviflora that can be controlled manually through light soil cultivation. However, manual weeding is labour intensive: 8-12 weedings are needed each year, with 15-20 people working per hectare for each session (Sanusi, 1977).

Chemical Control

C. crepidioides is susceptible to glyphosate and to glufosinate, but is not successfully controlled by paraquat beyond the seedling stage. Conversely, 2,4-D may be more effective on more mature plants (Laxmei de Silva and Ranamukaarachchi, 1994). Pre-emergence, oxyfluorfen is more effective than either linuron or diuron (Sanusi and Sabur, 1987; Laxmei de Silva and Ranamukaarachchi, 1994). Performance of paraquat may be improved by mixture with diuron (Isdiyanto and Pasaribu, 1988), but in some localities (for example, the highlands of Malaysia), where paraquat has been used repeatedly, highly paraquat-resistant biotypes have now developed (Itoh et al., 1992; Itoh, 1994).  Ismail et al. (2001a) report paraquat resistance in C. crepidioides growing in tomato and cabbage fields in the Cameron Highlands of Malaysia. Resistance may be associated with differential translocation of paraquat in resistant and susceptible biotypes, and with superoxide disumtase activity (Ismail et al., 2001a,b).

26/07/13 Updated by:

Julissa Rojas-Sandoval, Department of Botany-Smithsonian NMNH, Washington DC, USA

Pedro Acevedo-Rodríguez, Department of Botany-Smithsonian NMNH, Washington DC, USA