Devil’s thorn (Tribulus terrestris) is an annual plant in the caltrop family ( Zygophyllaceae ) widely distributed around the world, that is adapted to grow in dry climate locations in which few other plants can survive. Tribulus terrestris is a tap rooted herbaceous perennial plant that grows as a summer annual in colder climates. It is an erect herb forming a bush up. The leaves are soft, irregularly undulate, and toothed. The fragrant flowers are trumpet-shaped, white to creamy or violet. They rarely open completely.
Other common names includes; goat’s-head , Bullhead , Caltrop ,small caltrops , cat’s-head ,Devil’s eyelashes,devil’s-weed ,puncture vine , puncturevine ,and tackweed. Other common names in locally used in Kenya and East Africa includes; moonflower, amaduudu (Luganda), gathumba (Kikuyu), muana (Kiswahili), ngwata (Kamba).
The native range of Devils thorn is unclear but it is probably from the tropical regions of Central and South America.It is naturalized in all the world’s tropical and warm temperate of the world. It is one of the world’s most widespread weeds and has been recorded from over 100 countries. It is invasive in East Africa such as Kenya Uganda and in Tanzania.
Ecological and Environmental Requirements
It is native to warm temperate and tropical regions of the World in southern Europe, southern Asia, throughout Africa, and Australia. It can thrive even in desert climates and poor soil. A network of fine rootlets arise from the taproot to take advantage of soil moisture, by which the plant can survive in very arid conditions. Mainly found in roadsides, agricultural lands, disturbed areas and riverbanks.
Adaptations of Devil’s Thorn to Its Survival
- Having many ways of dispersal. Most of the weed is spread through the contamination of agricultural seeds.Both the seeds and capsules float on water, which provides an effective means of dispersal. Seeds are also dispersed via machinery, vehicles and mud. Pieces of root of the plant’s perennial species are also dispersed when dragged by cultivation equipment.
- It is adapted to a wide range of soils ranging from fertile to poor soils as well as acidic conditions. Hence colonisation of wide range of agricultural ecosystems.
- Dormancy of seeds. The seeds can lay dormant underground for years and germinate when the soil is disturbed.
- Production of many seeds. The weed has a bulbous capsule containing numerous seeds. Each plant bears 10 flowers which contain 100 seeds per capsule, resulting in 1000 seeds per plant.
- Produces poisonous thorns. This makes it difficult to control.
Effects of Devil’s Thorn as a Weed on Crops
- Competes with crops for nutrients, water and light hence weakening the crops and lowering their yields.
- Contaminates crop yields with their seeds hence lowering the produce quality.
- Increases cost of production of crops since it is capital intensive as well as Labour intensive to control the weed.
- It blocks irrigation channels
Management of Devils Thorn
Various methods are available which includes;
Two weevils, Microlarinus lareynii and M. lypriformis , native to India, France, and Italy, were introduced into the United States as biocontrol agents in 1961.
Mechanical methods/physical methods
This involves cultivation or mechanically uprooting of the weed.
Being a broad-leaved weed chemical control is generally recommended. There are few pre-emergent herbicides that are effective but most preferably it is targeted after the weed have emerged from the soil (postemergent), products containing 2,4-dichlorophenoxyacetic acid (2,4-D)and glyphosate as well as paraquat. Like most postemergents, they are more effectively maintained when caught small and young. Therefore the following herbicides can effectively be used in control of devil’s thorn as post emergence which includes;
- Agromine 100ml/20l. A broad spectrum selective systemic herbicide for the control of post-emergence broadleaf weeds in maize, rice and wheat fields and non-cropped areas It contains (Phenoxyacetic group) in form of dimethylamine salt (usually referred to by its abbreviation, 2, 4-D).
- Clampdown 200ml/20l. It contains its active ingredient with non-selective systemic herbicide glyphosate, a broad-spectrum systemic herbicide used to kill weeds both annual broadleaf weeds and grasses by inhibiting plant enzyme involved in the synthesis of the aromatic amino acids. It is effective as a post-emergence broadleaf and grass weeds in agriculture and non-cropped areas.
- Hurricane 150ml/20l. It is also a non-selective herbicide which is contact. It contains active ingredient inform of Paraquat.