Hyptis brevipes
(lesser roundweed)

H. brevipes is an annual plant of cultivated land and wastelands, including forest edges, wet ground and rice crops, and is favoured by continuous wet conditions, without a prolonged dry season. It is native to Mexico, the Caribbean and much of South America and has been widely introduced across South East Asia, where it has naturalized. H. brevipes may be accidentally introduced into a new area as a contaminant of seed, in particular with rice. It has been listed as a ‘principal’ weed of Malaysia and a common weed of Borneo, Philippines and Taiwan (Holm et al., 1979). In addition, PIER (2017) report that H. brevipes is invasive in Singapore, Thailand and Vietnam. Lorenzi (1982) describes it as a damaging weed of humid conditions along the coast, where it can develop into large infestations. H. brevipes is typically a weed of agricultural land, causing yield losses and a negative economic impact.

Up to 20 species in the genus Hyptis are also known to be invasive. The related H. suaveolens and H. capitata are both classified as noxious weeds in Northern Territory, Australia (Parsons and Cuthbertson, 1992) and H. brevipes is listed as an ‘invasive plant target list species’ in the same state (Glanznig and Kessal, 2004).

H. brevipes is considered native throughout Mexico, the Caribbean and much of South America, but has been widely introduced across South East Asia. It is reported as naturalized and invasive in Indonesia, Malaysia, Philippines, Singapore, Taiwan, Thailand and Vietnam (PIER, 2017; WSSA, 2017). Kostermans et al. (1987) describes H. brevipes as originating in Mexico but now being pantropical and having naturalized in Indonesia. Its occurrence in Africa, however, has not been confirmed. The plant known as ‘Hyptis brevipes’ in early Floras of Tropical Africa is now equated with H. lanceolata (Morton, 1963). The distribution of H. brevipes appears to be almost strictly tropical, though there is some occurrence in sub-tropical southern South America.

The risk of H. brevipes being introduced into new territories depends on a range of factors including trade in crop seeds and the thoroughness of plant quarantine regulations. Its introduction to continental USA from Mexico is particularly possible though the climate would only be suitable in the South East. The risk of introduction to Africa is quite high due to trade, experimental imports of rice seed and the climate in the tropical countries, which could be ideal for rapid establishment. Likewise, in many islands of the Pacific.

H. brevipes has been recorded from a wide range of both cultivated and natural habitats in tropical regions. It is mainly present in open ground but has some occurrence in forest margins, though it always requires high moisture levels and typically a wet tropical climate. In Indonesia, H. brevipes has been recorded up to 1200 m (Kostermans et al., 1987). In the Pantanal of Brazil, H. brevipes may dominate areas subject to periodic flooding (Almeida et al., 2014).

H. brevipes is primarily a weed of rice, especially in South East Asia, including Malaysia (Yong and Goh, 1977). In Indonesia it is noted to be a weed in rain-fed and upland rice fields, grasslands, rubber, cacao, young oil palm and sugar cane plantations and orchards (Knowledge Management Center on Topical Biology, 2017). It is also listed among weeds in mung bean in Indonesia (Bangun et al., 1986) and in Phaseolus beans in Brazil (Laca-Buendia et al., 1989).

Genetics

No chromosome counts have been found for H. brevipes however, Morton (1993) records a chromosome count of 2n = 64 for the closely-related H. lanceolata in West Africa.

Reproductive Biology

The flowers of H. brevipes have characteristics suiting them to pollination by insects. In Indonesia Jasmi (2017) records that H. brevipes flowers throughout the year and is visited by Apis cerana bees. Other Hymenoptera are recorded visiting the flowers in Singapore (Soh and Ngiam, 2013).

No information has been located on germination requirements or longevity but the related H. suaveolens is known to require light for germination (Wulff and Medina, 1971).

Physiology and Phenology

H. brevipes is an annual, short day plant. Panda (2005) found that at least 19 short days were required for induction of flowering. However, a more detailed study by Zaidan et al. (1991) found an interaction with temperature such that at higher temperatures, over 20°C, only 10 short day cycles were needed. Long days were inhibitory to flowering.

Population Size and Structure

In the Brazilian Pantanal, soil sampling indicated over 6000 seeds per m² (Bao et al., 2014)

Environmental Requirements

H. brevipes clearly requires fairly continuous moisture and warm temperatures. It can tolerate partial shade but not full shade.

Environmental

• Soil improvement

General

• Sociocultural value

Materials

• Pesticide

Medicinal, pharmaceutical

• Source of medicine/pharmaceutical
• Traditional/folklore

In Brazil, the closest related species, H. lanceolata, is distinguished by shorter calyx lobes (up to 1.5 mm long) and trichomes absent or appressed (Harley, 2012). H. capitata has larger heads, about 2 cm across on longer peduncles, at least 1.5 cm. It also has a ring of hairs inside the calyx, absent in H. brevipes. The related H. suaveolens and H. pectinata both have fewer (up to 5) larger flowers in each head, while H. brevipes has many, smaller flowers in dense heads up to 1.5 cm across.

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.

Prevention

SPS Measures

H. brevipes is included in the Northern Australia Quarantine Strategy (NAQS) invasive plant target list (Glanznig and Kessal, 2004) and is listed as a Prohibited Weed Species for Australia (Biosecurity Australia, 2002).

Control

Physical/Mechanical Control

As an annual weed, H. brevipes may be controlled by hand-pulling, hoeing and other routine weeding operations.

Chemical Control

Kostermans et al. (1987) indicate that MCPA and 2,4-D amine or ester are suitable for control of H. brevipes in rice. There is little other information on chemical control of H. brevipes but in Australia, recommendations for control of the related H. suaveolens include atrazine in sorghum and 2,4-D, dicamba, clopyralid and picloram in other situations where suitable (Parsons and Cuthbertson, 1992).

There is a serious lack of information on many aspects of the biology of H. brevipes especially regarding its germination requirements. There is also very little information on the use of herbicides and other control methods.

22/02/17 Original text by:

Chris Parker, Consultant, UK

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