Who will stop this parasitic weed's fast spread?

Plants covered by the parasitc dodder weed in Western Kenya. Photos: Jeckonia Otieno

A parasitic weed is slowly but surely choking vegetation in parts of Rift Valley and Western Kenya.

The dodder weed, which is rather new in Kenya, is not only attacking trees but also tea farms. Not only is it posing a threat to this region’s ecosystem, it is also affecting the livelihood of thousands of people.

What has baffled farmers, locals and scientists alike is the ease with which this seemingly rootless plant attaches itself, engulfs and then kills the host plant.

It is also known for host jumping where it moves to other plants not necessarily neighbouring the one to which it is attached. During its initial stages, the plant has roots on the ground but these completely detach once it has attached itself to the host plant. This means it can spread as far as it likes since it is not confined by roots to one spot.

In Siaya, for instance, the plant has set upon hedges with a vengeance.

“Most of the fences it has attacked are left bare and we have also noted it in a forest around Gem Ndere,” says John Wilfred, a member of the Kenya Forest Working Group.

Wilfred says the weed was first noticed in March last year at Gem Madeya and has since then spread across several acres in just a few months. He says this is causing panic among residents who feel helpless to contain its spread, which they speculate is being fueled by birds’ migratory patterns.

But Siaya is not alone as the weed has been spotted in different parts of Kenya where it is wreaking havoc with reckless abandon. In Nandi, tea bushes, fences and trees have been under attack since 2013.

Yet despite the havoc being caused by this weed, neither county or national government agencies are yet to commit to eliminating it. The only action that has so far been taken is exchange of letters addressed to different players and counties about the dangers of the weed. The best these letters have done is ring a bell on how fast the weed is spreading.

Due to dodder weed’s attack on tea plantations, a letter was written to the county executive committee members of Nandi, Uasin Gishu and Kericho counties on February 17, 2014, by the then director of Tea Research Foundation of Kenya - Dr Eliud Kireger.

The letter read: “Reference is made to the above parasitic weed (Cuscuta sp) commonly referred to as Dodder, which has been reported attacking several indigenous trees, shrubs and recently tea bushes in Nandi County and the neighbouring counties. Dodder being a parasitic weed is difficult to eradicate without destroying the plants on which it is anchoring.

Thus this weed should be regarded as a noxious weed hence combined effort is required for its containment.”

The letter went ahead to request for establishment and documentation of how extensive it has spread, including patterns and direction of spread in new areas. The research was expected to include its behaviour on agroforestry, fruit trees and crops among other plants.

Towards the end, the letter states: “Containment of this weed is very critical and a collaborative approach to prevent the problem is necessary.”

Attached to the letter was an article published in the Tea News which is a publication of the Tea Board of Kenya. The tea bulletin documented that the weed attacks different plant species and has an affinity for live fences.

Dr Kireger’s letter followed another letter by Dr John Bore, acting institute director of Tea Research Foundation of Kenya on February 14, 2014. It stated that reports indicated the weed whose existence in Kenya was first reported in 2007 attacks mostly Mauritius thorn, K-apple, bougainvillea, mango, Nandi Flame, loquats, acacia and tea trees.

“There are unconfirmed reports that it was introduced as an ornamental flower plant.

Several surveillance visits to tea fields in a number of counties, Nandi, Kericho, and Vihiga counties and reports reaching Tea Research Institute from Nandi County indicates that this weed is fast spreading hence urgent action should be taken to manage (its spread),” read part of the letter.

Further, the letter noted that dodder weed tends to be more prominent on fences near many day schools in the named areas and could probably be attributed to spreading by school children.

It therefore suggested a sensitisation of all schools within the counties affected to start efforts to mitigate its spread.

Despite the warnings and letters, this writer found that no major work has been done except for a report by Dr Evelyn Cheramgoi, K. Sitienei, D. Talaam, W. Kirui and N. Kigen which was the basis of the two letters that emanated from Bore and Kireger. This comes even as the weed continues to destroy vegetation and affect eco-systems.

According to Kenya Forestry Research Institute Principal Researcher Eston Mutitu, the plant is now common in Bungoma, Busia, Siaya, Kisumu and Migori counties.

Mutitu says having talked to locals in these areas, they confirm that the weed started appearing about five years ago. However, it is relatively new in Siaya where residents do not understand its affinity for hedges.

He says that proper research on the plant is yet to start despite its effects being profound but meetings have been held with officials from the Kenya Agriculture and Livestock Research Organisation to start planning on how to tackle the problem.

“This is not the only weed that is attacking plants. There are other weeds that have similar habits that are attacking plums, pears and peaches in Njambini and Kiambu,” Mutitu said.

A report attached to Bore’s letter states that dodder kills other plants by feeding off them because it has no chlorophyll to produce its own food, hence its yellowish nature.

The reports notes: “This parasitic action drains the host of vital resources needed for healthy growth. Impact varies from moderate to severe reductions of plant growth and, in some cases, complete loss of vigour and death.

The severity of an infestation depends on the growth stage of the host plant at the time of initial dodder attachment. It can cover and kill most large shrubs and small trees. The weakened state of infected plants also predisposes them to diseases and insect and nematode invasions.”

As part of mitigation measures, the report suggests, pruning the area of attachment which Mutitu says could pose a danger because this will lead to destruction of many host plants. Also burning the plant has been suggested as well as pushing for legislation to list dodder as a prohibited noxious weed.

The report’s final point states that Tea Research Foundation is looking into experimental trial set ups.