Overview

Devil’s thorn, scientifically known as Tribulus terrestris, belongs to the caltrop family and is an annual plant found worldwide. It has adapted to thrive in dry climate regions where only a few other plants can survive. This article explores the characteristics, distribution, ecological requirements, adaptations, and effects of Devil’s thorn as a weed on crops. Additionally, it discusses various methods of managing Devil’s thorn.

Characteristics of Devil’s Thorn

Devil’s thorn is an erect herbaceous perennial plant that grows as a summer annual in colder climates. It forms a bush-like structure and has soft, irregularly undulate, and toothed leaves. The fragrant flowers are trumpet-shaped and come in white, creamy, or violet colors. However, these flowers rarely open completely.

Different Names for Devil’s Thorn

This plant goes by various common names, such as goat’s-head, bullhead, caltrop, small caltrops, cat’s-head, devil’s eyelashes, devil’s-weed, puncture vine, puncturevine, and tackweed. In Kenya and East Africa, it is also known as moonflower, amaduudu (Luganda), gathumba (Kikuyu), muana (Kiswahili), and ngwata (Kamba).

Distribution of Devil’s Thorn

The exact native range of Devil’s thorn remains uncertain, but it is believed to originate from the tropical regions of Central and South America. It has become naturalized in tropical and warm temperate regions worldwide and is considered one of the most widespread weeds, present in over 100 countries. In East Africa, including Kenya, Uganda, and Tanzania, it has become invasive.

Ecological and Environmental Requirements

Devil’s thorn is naturally found in warm temperate and tropical regions across the world, including southern Europe, southern Asia, Africa, and Australia. It can even survive in desert climates and poor soil conditions. The plant possesses a taproot with a network of fine rootlets that helps it access soil moisture, allowing survival in extremely arid conditions. It is commonly found in roadside areas, agricultural lands, disturbed areas, and riverbanks.

Adaptations for Survival

Devil’s thorn has various adaptations that aid its survival and spread:

1. Dispersal Methods: The weed spreads through agricultural seed contamination, floating seeds and capsules carried by water, machinery, vehicles, and mud. Pieces of the perennial species’ root are also dispersed when cultivation equipment drags them.

2. Soil Adaptability: It can colonize a wide range of soils, including fertile and poor soils, and tolerate acidic conditions. This enables it to thrive in diverse agricultural ecosystems.

3. Dormancy: Devil’s thorn seeds can remain dormant underground for extended periods and germinate when the soil is disturbed.

4. Abundant Seed Production: Each plant bears 10 flowers, with each flower containing a capsule that holds around 100 seeds. This results in approximately 1000 seeds per plant.

5. Thorny Defense: Devil’s thorn produces thorns, which make it challenging to control and remove.

Impact on Crops

Devil’s thorn, as a weed, negatively affects crops in several ways:

1. Competition: It competes with crops for nutrients, water, and light, thereby weakening the crops and reducing their yields.

2. Seed Contamination: The weed contaminates crop yields with its seeds, leading to a decline in produce quality.

3. Increased Production Costs: Controlling Devil’s thorn requires significant capital and labor investments, resulting in increased production costs for farmers.

4. Irrigation Blockage: The weed can block irrigation channels, disrupting the water supply to crops.

Management of Devil’s Thorn

Several methods can be employed to manage Devil’s thorn:

1. Biological Methods: Introducing weevils, such as Microlarinus lareynii and M. lypriformis, as biocontrol agents has been effective in controlling Devil’s thorn in some regions.

2. Mechanical Methods: Cultivation or mechanical uprooting of the weed can help manage its spread.

3. Chemical Control: Since Devil’s thorn is a broad-leaved weed, chemical control is commonly recommended. Postemergent herbicides containing 2,4-dichlorophenoxyacetic acid (2,4-D), glyphosate, or paraquat can be used effectively, especially when the weed is young and small.

  • Agromine: A selective systemic herbicide containing 2,4-D, which effectively controls post-emergence broadleaf weeds in maize, rice, wheat fields, and non-cropped areas.
  • Clampdown: A non-selective systemic herbicide containing glyphosate, used to kill both annual broadleaf weeds and grasses in agriculture and non-cropped areas.
  • Hurricane: A contact herbicide containing paraquat, effective against a wide range of weeds.

Conclusion

Devil’s thorn is a resilient plant that can survive in dry climates where other plants struggle. Its adaptability, extensive seed production, and thorny defense make it a challenging weed to control. However, through biological, mechanical, and chemical methods, farmers can effectively manage Devil’s thorn and protect their crops from its detrimental effects.

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