Datura ferox
(fierce thornapple)

A number of sources (e.g. Parsons and Cuthbertson, 2001; USDA-ARS, 2014) indicate that, unlike other Datura species, D. ferox is native to China. However, according to Flora Zambesiaca (2014) it is ‘native to southern North America (but for a long time said to be native to China based on an error from Linnaeus)’. It is not listed in Flora of China (2014). It is unlikely that D. ferox is native to Bolivia and other parts of South America, as indicated in some floras; the species of Datura occuring in South America might have been introduced in pre-Columbian times (Geeta and Gharaibeh, 2007). In Australia, D. ferox is much less frequent than D. stramonium (Parsons and Cuthbertson, 2001).

D. ferox has been widely spread by humans and is now present in Japan, India, Israel, south and east Africa, Europe, California, South America, Easter Island, Australia, New Zealand and New Caledonia.

D. ferox occurs in warm-temperate and subtropical regions, mostly in open situations on fertile soils. It grows on disturbed sites such as roadsides, waste places, embankments, river flats and stock yards. It is a weed of summer crops in many parts of the world, particularly cotton, soybeans, peanuts, maize, sorghum, sunflower and vegetables.

D. ferox is a weed in summer crops, including maize, soybean, peanuts, grain sorghum, potato, sunflower and Cucurbitaceae (Parsons and Cuthbertson, 2001; Torres et al., 2013a,b).

Genetics

Chromosome number: 2n = 24 (Bergner and Blakeslee, 1932). Natural hybrids between D.ferox and D. stramonium have been reported from Australia (APNI, 2013). D. ferox is self-compatible and self-pollinating, although cross-pollination yields a higher number of seeds (Torres et al., 2013 a,b). The cytogenetics of the genus Datura is the subject of a volume edited by Avery et al. (1969).

Reproductive Biology

As an annual, reproduction of D.ferox is by seed only. No other plant parts have been observed to grow into new plants, but plants may remain alive if roots become partly destroyed (Parsons and Cuthbertson, 2001). Number of seeds per fruit ranged from 96 to 227 in plants from Argentina (Torres et al., 2013b).

Average number of emerged seedlings in a maize field in Central Spain was 288 and 188 plants m^-2, respectively (Dorado et al., 2009).

Physiology and Phenology

D. ferox contains toxic alkaloids, including atropine, scopolamine and hyoscyamine (Vitale et al., 1995; Piva et al., 1997). The content of these compounds varies with availability of nitrogen, light intensity and temperature (Parsons and Cuthbertson, 2001). In South American D.ferox plants, scopolamine may constitute 98-100% of total alkaloids (Piva et al., 1997). Seeds also contain carbohydrate-binding proteins such as ß-Galactosidase (Plá et al., 2003).

Seeds may germinate throughout the year if soil moisture is high enough (Parsons and Cuthbertson, 2001). 10 mm of rain or irrigation water is sufficient to cause germination once seed dominancy is broken. Seeds require an after-ripening period of several months because a chemical inhibitor in the seedcoat must be leached out or broken down before germination takes place. Therefore, germination in the field is spread over several months, making control strategies difficult (Parsons and Cuthbertson, 2001). Germination rates vary with environmental conditions but may be low. Thus, germination rates of seeds collected from corn fields in Central Spain ranged from 2 ± 1.7 % to 11 ± 3.6 % (Dorado et al., 2009a).

According to Soriano et al. (1964) seeds need light and alternated temperatures to germinate. Martínez-Ghersa et al. (2006) emphasized that seedling emergence therefore takes place after soil cultivation in summer crops, or any other soil disturbances (Scopel et al., 1991).

Seedlings grow quickly if temperature and soil moisture are high enough. Growth rates of 2 cm per day have been recorded. Flowers may be produced at the age of 2-5 weeks. Flowering and fruiting continue throughout the summer.

The large and scented flowers open at night and are pollinated by hawkmoths, sphingids, coleopterans and Apis mellifera in soybean crop fields in Argentina (Torres et al., 2013a). D. ferox may have two flowering peaks in a year (Torres et al., 2013b).

Environmental Requirements

Seeds need light and alternating temperatures in order to germinate (Soriano et al., 1964). In summer crops, seedling emergence is thus promoted by cultivation (Ballaré et al., 1988).

Growth depends on density. In a common garden study, D. ferox plants were grown at 32, 100 and 240 plants m^-2 (Ballaré et al., 1988). Seedlings responded rapidly to increased plant density by producing longer internodes and allocating more dry matter to the stem relative to leaves. The number of leaves did not change significantly (Ballaré et al., 1988).

Medicinal, pharmaceutical

• Source of medicine/pharmaceutical

D. quercifolia can be distinguished from D. ferox by more purplish coloration in foliage; corolla and anthers, slightly downy versus glabrous; and spines somewhat less stout (Houmani et al., 1999).

A number of related species have a similar appearance and similar properties to D. ferox, and are also weeds in various places: common thornapple (Datura stramonium L.), downy thornapple (Datura inoxia Mill. = D. innoxia Mill.), hoary thornapple (Datura metel L.) and hairy thornapple (Datura wrightii Rogel).

Both common thornapple (D.stramonium) and D.ferox produce erect fruit capsules on straight stalks. Seeds of both species are black to greyish. In contrast, fruit capsules of other thornapples (Datura leichhardtii, D. metel, D. inoxia, D. wrightii) appear on curved stalks and their seeds are brown to yellow. Flowers of D.ferox are shorter (4-6 cm long) compared to flowers of D. stramonium (up to 10 cm long). A distinguishing feature of D.ferox is the long spines on the fruit capsules.

Datura species are annual, whereas members of the closely related genus Brugmansia are perennials.

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.

Physical/Mechanical Control

With single plants it is best to hand pull or hoe them before fruit form (Parsons and Cuthbertson, 2001). Larger infestations are best controlled by cultivation, preferably at the seedling stage (Parsons and Cuthbertson, 2001). Repeated cultivation is necessary as seedlings emerge over a long period from the soil seed bank.

Chemical Control

Thornapples are susceptible to 2,4-D in the seedling stage and young growth stages but become resistant as they mature (Parsons and Cuthbertson, 2001). Other non-selective herbicides include atrazine, diquat, paraquat and glyphosate. The following herbicides are available for use in specific crops: acifluorfen in soybeans and peanuts; bentazone in soybeans, other beans and peanuts; 2,4-DB in certain varieties of peanuts; dicamba in grain sorghum and maize; metolachlor in maize, and picloram + 2,4-D in summer cereals (Parsons and Cuthbertson, 2001).

16/12/13 Original text by:

Ewald Weber, Consultant, Switzerland