This archive report was first published on 19 June 2020.
Kenya's forests and agricultural sector are facing a silent threat in the form of two invasive weeds: Cascuta campestris, also known as Dodder plant, and Ipomoea alba, commonly referred to as moonflower or moon vine.
According to Dr. Eston Mutitu, a research scientist at the Kenya Forest Research Institute (Kefri), these weeds are noxious climbers with no serious insect or disease problems, and they kill trees by suffocating them.
Ipomoea alba, also known as Windia in Kikamba, has been present in Kenya since the colonial days and is widespread in the eastern part of the country. It produces sweet-scented white flowers that open in the evening and close when touched by the morning sun.
On the other hand, Dodder, which is native to the Americas, is a recent invader but has spread rapidly across the country, with sightings reported in nearly all regions, including Busia, Kisumu, Bungoma, Kakamega, Uasin Gishu, Elgeyo-Marakwet, Kajiado, Machakos, Makueni, Nairobi, and Kilifi.
Initially, Dodder was limited to public forests but has increasingly been attacking private plantations. In 2018, My Cypress, Grevillea, and Blue gum trees in Webuye were attacked.
Both weeds start their destructive lives as seedlings in the soil before attaching to a host plant, usually a tree. For Cascuta, once it is united with its host, the first portion of its stem withers, and the weed is no longer connected with the ground. It obtains all its food and water from its host.
Dr. Mutitu warns that it is becoming a nightmare, as these weeds kill by suffocation and starvation. Once they attach themselves to a tree, they grow rapidly, completely covering its branches and leaves, preventing photosynthesis from happening.
Public awareness is critical to fight these weeds, as some people spread them willingly by planting them in their homes, especially on their hedges. The moon vine is attractive due to its sweet scent, while Cascuta has bright yellow and orange colors.
Scientists at Kefri are analyzing Cascuta to understand the biology of host plants, with a view of coming up with a mitigation strategy. Among the possibilities under consideration is chemical and biological control.
However, the challenge scientists face is that hundreds of plants, including crops, are hosts. In the meantime, farmers can control these weeds by manually plucking them from the affected plant, regularly inspecting their hedges and the ground under their trees, and uprooting the affected tree or cutting off branches and burning them together with the weed.
Chemical control is also an option, but farmers should seek advice from experts on how to apply the chemicals.
