Bidens subalternans

Bidens subalternans DC. is an annual herbaceous plant belonging to the Asteraceae family. Within the agricultural sector, it is primarily recognized as a significant weed species that poses a substantial threat to crop productivity due to its aggressive growth habits and high reproductive efficiency.

Originating from South America, Bidens subalternans has demonstrated a remarkable ability to naturalize across various global regions, particularly in tropical and temperate zones. Its range of cultivation has expanded significantly, as the plant effectively colonizes disturbed environments, roadsides, and cultivated fields, competing directly with major cash crops.

Botanically, the plant is characterized by a branched stem that can grow to over a meter in height. Its leaves are typically pinnately compound, and the inflorescences consist of small yellow flower heads. A key adaptive feature is the presence of hooked awns on the seeds, which facilitate dispersal by sticking to animal coats, human clothing, and agricultural machinery, making it difficult to contain.

The plant thrives in a variety of soil types, preferring moisture-retentive, nutrient-rich soils but showing high tolerance to environmental stress. Effective agronomic control involves a combination of mechanical techniques, such as early-season cultivation and tillage, as well as the strategic use of herbicides. Crop rotation remains one of the most vital strategies to break the germination cycle of this species.

While the plant has no beneficial uses in commercial agriculture, it causes extensive economic damage. The primary agricultural impacts include:

• Direct resource competition for nutrients, sunlight, and soil moisture.
• Increased production costs associated with weed control and crop cleaning.
• The risk of hosting secondary pests and pathogens that affect staple crops.
• Reduction in harvest quality and yield potential due to heavy weed pressure.