Commelina benghalensis

Commelina benghalensis, popularly known as trapoeraba, beijinho, flor-de-são-joão or commelina, is a herbaceous plant of the Commelinaceae family.

Originating from Asia, specifically from a broad region that includes India, China and Southeast Asia, this species has spread throughout Latin America, Africa and Australia, becoming one of the most aggressive invasive exotic plants in tropical and subtropical regions.

Its presence is particularly problematic in crops such as soybeans, corn, sugar cane and vegetables, where it competes intensely for resources and can cause significant productivity losses.

Biology of Commelina benghalensis

Although the epithet benghalensis suggests an association with the Bengal region (India and Bangladesh), botanical studies indicate that the native distribution of the species is wider, covering a large part of Southeast Asia, including India, China and Southeast Asian countries (Faden, 1983).

The plant was introduced to other regions through human activities such as trade and agriculture, and is now considered an invasive weed in several countries.

C. benghalensis It is an annual or perennial herbaceous plant, with succulent and fragile stems that can grow up to 50 cm in height. The leaves are alternate, with ovate blades and parallel veins.

The flowers are arranged in spike-shaped inflorescences, with blue or white petals, and the fruits are loculicidal capsules (which open longitudinally along the locules) containing rounded seeds, light brown to black in color, with chemical dormancy that allows asynchronous germination.

Reproduction occurs both sexually, through hermaphrodite flowers with protandry (ripening of the stamens before the stigma), facilitating cross-pollination by insects such as bees, and vegetatively, through stem fragments that root at the nodes.

In addition, the plant produces cleistogamous flowers (which self-fertilize without opening), increasing its reproductive flexibility (Maheshwari & Maheshwari, 1955). The seeds present chemical dormancy, ensuring germination over time.

Adapted to a wide range of climates and soils, C. benghalensis uses C3 photosynthesis and exhibits allelopathy, releasing substances such as phenolic acids and flavonoids that inhibit the growth of other plants (Ghosh et al., 2019).

Studies have demonstrated its phytotoxic potential in species such as Lonchocarpus sericeus. The plant is also tolerant of drought conditions once established, but requires moist soils for initial germination.

The life cycle can be annual or perennial, depending on environmental conditions such as climate and agricultural management.

In humid tropical regions, the plant tends to be perennial due to the absence of a prolonged dry season, while in climates with marked dry periods, it behaves as an annual.

Germination occurs throughout the year in moist conditions, allowing the plant to compete effectively with commercial crops for resources such as light, water and nutrients.

Agricultural impact

C. benghalensis is a major weed in several crops, including soybeans, coffee, rice and corn. Its presence can significantly reduce crop productivity.

In soybeans, although there is no specific quantitative data on yield losses, studies indicate that lack of adequate control can lead to substantial reductions in productivity (Riar et al., 2016).

In coffee, research has shown that coexistence with C. benghalensis can cause losses of up to 50% in productivity due to competition for resources (Dias et al., 2005).

The plant is also difficult to control due to its ability to regenerate from stem fragments and its resistance to herbicides.

Integrated management strategies

The control of C. benghalensis requires an integrated approach, combining chemical, mechanical, cultural and biological methods.

The plant has developed resistance to several herbicides, including glyphosate, 2,4-D, and paraquat (IntechOpen, 2013). Effective herbicides include s-metolachlor, clomazone, and flumioxazin, often used in mixtures or sequentially (Monquero et al., 2005). In crops such as coffee, mixtures of carfentrazone-ethyl and glyphosate have been shown to be effective (Weed Control Journal, 2001).

Research indicates the potential for biological control with the fungus Phoma commelinicola, which has shown efficacy against Commelina diffusa and can be adapted to C. benghalensis (MDPI, 2015). Other agents, such as pathogenic fungi (Colletotrichum gloeosporioides) and specific insects are under study, but there are still no commercialized products (IntechOpen, 2013).

Cultural practices such as crop rotation, use of cover crops, and proper management of crop residues can reduce infestation. However, mechanical control is challenging due to the plant's ability to regenerate from stem fragments. Manual removal should ensure complete removal of the plant from the soil to prevent regrowth.

Click here to see which herbicides are registered for the control of Commelina benghalensis