Emilia sonchifolia
(red tasselflower)

Emilia sonchifolia is an annual herb believed to be native to China and South-East Asia. Since spreading from its natural range, E. sonchifolia now has a pan-tropical distribution and is naturalized elsewhere in Asia, as well as in Australia, the Pacific Islands, Africa and the Americas. This species has been reported as a weed for a number of crops and has been shown to reduce yields and act as a reservoir for crop pathogens. Currently it is listed as invasive in India, Mexico, Brazil, Paraguay, Costa Rica, the Galapagos, Puerto Rico, the Virgin Islands, Dominican Republic, Trinidad and Tobago, Madeira, Réunion, Hawaii and on many other islands in the Pacific Ocean. Mechanical control has been shown to be effective, and chemical control has been effective in some annual and perennial crops.

The exact native range of E. sonchifolia is still uncertain (USDA-ARS, 2018). It is considered native to Asia (China, Southeast Asia) but it now has a pan-tropical distribution and can be found naturalized in Africa, North, Central and South America, the West Indies, Oceania and several islands across the Pacific and the Indian Ocean (Pruski and Robinson, 2018; GRIIS, 2018; PIER, 2018; PROTA, 2018; USDA-ARS 2018).

Growing at elevations ranging from sea level up to 3000 m, E. sonchifolia thrives under a wide range of environmental conditions across tropical and subtropical regions. It is a common weed in open grasslands, waste areas, roadsides, arable crops, pastures, forest edges, coastal thickets, weedy slopes, riverbanks and paddy ridges. It also grows in partially shaded areas beneath coffee, oil palm and tea plantations (Pruski and Robinson, 2018; Flora of China, 2018).

Within and outside its natural distribution range, E. sonchifolia is a very common weed of field crops, and can be found in virtually any annual or perennial plantation crop.

Genetics

The chromosome number reported for E. sonchifolia is 2n=10 and 2n=20 (Xie et al., 2003; Flora of China, 2018).

Reproductive biology

The flowers of E. sonchifolia are hermaphrodites and are pollinated by insects (i.e. bees and flies) and by wind. This species is self-fertile (Pruski and Robinson, 2018; PFAF, 2018).

Physiology and phenology

In China, E. sonchifolia flowers from July to October (Flora of China, 2018). In Central America and Mexico, this species has been recorded flowering throughout the year (Pruski and Robinson, 2018; Vibrans, 2019). In the USA it produces flowers all year, but mostly from October to March (Flora of North America, 2018).

Longevity

Emilia sonchifolia is a fast-growing annual plant (Flora of China, 2018).

Activity patterns

As long as soil moisture is adequate, E. sonchifolia will germinate throughout the growing season in Nigeria (Holm et al., 1997) with plants completing their life cycle in about 90 days. Two types of seed may be distinguished by the colour of the achene. The female outer circle of florets of a flower head produce reddish-brown achenes while those from inner hermaphrodite florets are off-white (Marks and Akosim, 1984). A larger proportion of both types germinate at 27°C than at 30°C but only those which develop from outer florets germinate under deep shade. While low levels of germination (4%) will occur when seeds are buried as deep as 4 cm in the soil, plants will only emerge from seed near to the surface. Only 3% of seedlings germinating at a depth of 1 cm emerged in trials in Sri Lanka compared with 29% of those placed at 0.5 cm (Pemadasa and Kangatharalingam, 1977), suggesting that occasional deep tillage may be a useful control measure.

Environmental requirements

Emilia sonchifolia prefers to grow in moist tropical areas with temperatures ranging from 20°C to 30°C (but can tolerate 10-40°C) and mean annual rainfall of 1000-2000 mm. It prefers well-drained soils in a sunny position with a pH of 4.5-6.5. Plants are drought tolerant once established (Pruski and Robinson, 2018; Flora of China, 2018; PIER, 2018; Fern, 2019). It is particularly tolerant of acid conditions, and is an early colonizer of newly cleared peat soils in Malaysia (Wee, 1970).

Movement and Dispersal

Emilia sonchifolia spreads by seed. The fruit carries a pappus of capillary-like bristles that facilitates wind-dispersal. Seeds can be secondarily dispersed by water, as a contaminant in crop and pasture seeds, on soil and adhered to vehicles and agricultural machinery (Pruski and Robinson, 2018; Flora of China, 2018; Flora of North America, 2018; Fern, 2019).

General

• Ornamental

Human food and beverage

• Vegetable

Medicinal, pharmaceutical

• Source of medicine/pharmaceutical

Emilia sonchifolia is most likely to be confused with Emilia coccinea, with which it can hybridize (Olorode and Olorunfemi, 1973). E. coccinea is also found in Brazil, the Caribbean, Colombia, Costa Rica, El Salvador, Honduras, Mexico, USA, Venezuela, Sri Lanka and much of West Africa (Adams, 1963; Holm et al., 1979; Fournet and Hammerton, 1991). In East and Central Africa both species occur in highland areas of Malawi (Banda and Morris, 1985), while E. coccinea is widespread throughout more humid areas of Kenya, Tanzania and Uganda (Blundell, 1992), and is also present in Angola, Mozambique, Zimbabwe and Zambia (Bolnick, 1995).

E. coccinea may be distinguished by having about 8 involucral bracts, somewhat less than the 15 found in E. sonchifolia. E. coccinea is recognized by yellow flowered forms in West Africa and scarlet flowered forms in East/Central Africa, while those of E. sonchifolia are mauve or rarely white (Adams, 1963). However, flower colour in E. sonchifolia varies greatly around the world and particular care needs to be taken when considering this character.

Emilia sonchifolia looks similar to E fosbergii and E. coccinea. These species can be distinguished based on the following vegetative and floral traits (Pruski and Robinson, 2018):

Emilia sonchifolia: Basal and lower leaves lyrate-pinnatifid; involucres narrow-cylindrical, corollas included to only slightly exserted; corollas usually pink or lavender, lobes 0.5-0.8 mm; disc floret styles indistinctly appendiculate, appendages to 0.1 mm, no longer than broad, convex.

Emilia coccinea: Basal and lower leaves shortly petiolate; involucres broad-cylindrical to hemispherical, corollas moderately to well-exserted; corollas lobes 1.1-2.2 mm; disc floret styles obviously appendiculate, appendages 0.2-0.3 mm, caudate. Leaf margins nearly subentire; involucres campanulate, about as long as broad, corollas well-exserted; corollas bright orange to red, lobes 1.6-2.2 mm.

Emilia fosbergii: Basal and lower leaves shortly petiolate; involucres broad-cylindrical to hemispherical, corollas moderately to well-exserted. Leaf margins usually coarsely dentate; involucres broad-cylindrical, (1-) 2× as long as broad, corollas moderately exserted; corollas usually pale red or pinkish-red, lobes 1.1-1.6 mm

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.

Emilia sonchifolia is easily controlled mechanically, while selective chemical control can be achieved in some annual and perennial crops. A co-formulated mixture of pretilachlor and dimethametryn, a mixture of piperophos with propanil or oxadiazon alone, all applied at 5 days after sowing provided 8-12 weeks control in upland rice in Nigeria (Enyinnia, 1992). Pre-emergence applications of cyanazine, metribuzin or imazaquin, or post-emergence application of a mixture of bentazone, fomesafen and sethoxydim allow selective control in soyabean (Barros, 1989; Barros et al., 1992). Sethoxydim applied alone has not provided control in trials with either cotton or soyabean in Brazil (Beltrao et al., 1983; Barros et al., 1992). A number of options are available for residual control in plum orchards including glyphosate mixtures with diuron, simazine or terbacil, MSMA mixed with diuron, or paraquat mixed with simazine (Almeida et al., 1987). For Eucalyptus grandis, oxyfluorfen provides control of E. sonchifolia for up to 180 days following application (Silva et al., 1995). Atrazine provides excellent control in sugarcane in Hawaii (Olney, 1971).

27/02/18 Updated by:

Dr. Julissa Rojas-Sandoval, Department of Botany-Smithsonian NMNH (Rojas-SandovalJ@si.edu)