A number of farmers in Kajiado County have been complaining that a strange weed has invaded their farms. The weed is called Bush Morning-glory or Ipomoea carnea (sub-species Fistulosa). Today, I will try to shed some light on it.
It is a shrub which is usually one to three metres tall, with an erect or ascending habit when growing in open positions. In shady places, it is more likely to adopt a climbing habit, with twining stems up to five metres long. It invades fallow land and shallow wetlands. It is extremely hardy and is resilient to several forms of chemical and biological control.
It originated from South America and Central America in the area covering Argentina, Paraguay, Brazil, Bolivia, Peru, Ecuador, Colombia, Venezuela, the Guyanas, Panama and northern Mexico. It has spread to Asia, Africa and North America. In Africa, it has already been reported in South Africa, Zimbabwe and Zambia.
It is poisonous and affects central nervous systems. The symptoms include difficulty to stand up, lack of coordination in muscular movements, intense tremors, and loss of equilibrium in goats. Cattle are affected only if they consume the plant in large quantity.
It is classified as an invasive species. It inhabits banks of seasonal rivers and drainage channels. The weed is spread by stem fragments and seeds, which may be easily carried by flood water to new areas as well as moving livestock. The seeds are hairy, making it easy to be dispersed by water and air. Over-grazing encourages the growth of the weed. Shallow seasonal flooding encourages its proliferation. It spreads easily (because it is hardy), reproduces rapidly and grows very fast.
There is no chemical or biological method that can effectively control it. Cutting the weed and burning it or compositing it is the most effective way of dealing with it. Repeated cutting is required because the stump often sprouts.
The stump suffocates if submerged in water. The weed should not be allowed to spread and should be immediately cut as soon as it is appears. It should not be allowed to produce seeds nor should the cut parts be left on the ground to regenerate.
The weed can be used to develop industrial products and has medicinal uses.
- The writer is an associate professor, Department of Horticulture and Director, Directorate of Performance Contracting and Appraisal at JKUAT.