- Dodder has been spotted in counties including Nyamira, Kisii, Homa Bay, Kisumu, Vihiga, Kakamega, Bomet, and Nairobi.
- Weed and environmental scientist Prof. Ratemo Michieka says the weed is difficult to control using chemicals or herbicides.
- KEFRI warns that if left uncontrolled, dodder could cause serious food security threats by 2029.
A little-understood parasitic weed is rapidly spreading across the country, drying up hedges and other vegetation, and posing a potential food security threat to affected citizens.
The weed, identified as dodder and classified under the Cuscuta species, appears as a yellow-orange, leafless, thread-like vine that grows over its host’s leaves, branches, and stems, forming an entangled, smothering web.
This string-like parasite coils around other plants, eventually killing its host.The online encyclopaedia Britannica says Cuscuta includes about 145 species of leafless, twining, parasitic plants in the morning glory family (Convolvulaceae), which “are widely distributed throughout temperate and tropical regions of the world. Many species have been introduced with their host plants into new areas and are considered invasive.”
Dodder has been spotted in counties including Nyamira, Kisii, Homa Bay, Kisumu, Vihiga, Kakamega, Bomet, Kiambu, Taita Taveta and Nairobi.
Interviews reveal that, aside from affecting natural fences, the weed causes significant damage to other hosts, including tea, avocados, maize, sugarcane, and bananas.
Concern has gripped affected residents, who note that the parasite gradually strangles its host, and no effective method of destroying or controlling its spread is known.
Recently, a member of ScholarMedia Digital, a WhatsApp group of over a thousand scholars, educators, and other professionals, ignited a debate about the weed, with several expressing concern over its rapid spread.
“We have a dangerous parasitic weed destroying our fences, ornamental trees, flowers, and even crops,” wrote Kennedy Mogaka, Principal of Marindi Secondary School in Nyamira County.
Mr Mogaka noted that the weed was spreading quickly in Kisii and Nyamira counties and was particularly prevalent around Sironga and Marindi areas.
This writer also independently confirmed that the weed is affecting residents in Ikobe, Bosose, Ramba, and Ogango villages in West Mugirango Constituency, which borders the areas mentioned by Mr Mogaka.
In an interview, Mr Mogaka revealed that part of his school hedge had dried up due to the weed’s invasion, forcing them to cut it down.
“We cut the hedge to stump level, hoping the weed would die. Unfortunately, it reappeared as soon as the hedge regrew,” he said.
In Kisumu, Constance Sesera reported seeing the weed in Kakamega, Kisii, and other lake region counties and wondered about its origin.
“I’ve seen it in many places, and I was surprised to learn it doesn’t have roots. It’s very destructive as it kills its host,” Ms Sesera said.
Weed and environmental scientist Prof. Ratemo Michieka says the weed is difficult to control using chemicals or herbicides.
“I tried spraying during research trials, but the succulent tendrils were impervious to herbicides,” said Prof. Michieka, Chairperson of the National Research Fund (NRF) and Chancellor of Tharaka University, adding that the weeds should be removed manually and burned.
However, manual control is complicated as one may kill valuable host plants, such as tea and hedges, which have economic and aesthetic value.
Worse still, the parasite weakens its hosts, making them more susceptible to diseases, pests, and less resilient to environmental stresses like drought or extreme temperatures.
“You can’t afford to kill tea, coffee, or avocado. Kill the weed manually,” Prof. Michieka advised.
Agronomist Prof. Evans Basweti of Kisii University agrees there is no effective chemical or biological control for the weed.
“Remove dodder stems by hand and prune the affected plant to control it,” he said.
“Destroy the host, destroy the parasite,” added Peter Ndung’u, a retired principal and scientific research enthusiast.
“The Japanese dodder (Cuscuta japonica) is indeed becoming a menace,” wrote Elias Moturi of Kereri Girls’ High School, Kisii.
“You cut it, pull it off the fence, and burn it. That saved our fence and flower beds,” added Alfred Nyagaka, Deputy Principal of Bong’onta Secondary School.
Owing to the weed’s resilience and rapid spread, questions remain about how it reproduces, its host plants, and its survival adaptations.
“The main issue is its reproduction and spread. It must have high survival adaptation,” argued Charles Onditi, a veterinary surgeon and environmental audit specialist.
He suggested that browsers like goats could help control it, provided they are willing to eat it.
Linnus Nyakundi, another group member, said he had been advised to use a warm water and salt solution to kill the weed, but it didn’t work.
“Warm water just dissolves the salt into a brine solution, which kills most plants except halophytes, cotton, and a few others,” said Prof. Augustino Onkware of the University of Eldoret.
“I first saw dodder around Ahero in Kisumu County. I suspect humans transported it to other areas, possibly via sand used in construction,” said Julius Bosire, a member of the Agricultural Society of Kenya (ASK), Kisii branch.
Investigations could not determine whether killing the host would automatically eliminate the parasite or if it would find other means to survive.
“I don’t know if it has any use or economic value, as I haven’t even seen goats eating it,” said Peterson Otieno of Mamboleo village, Kisumu County.
Prof. Maurice Amutabi of the Technical University of Kenya (TUK) noted the weed has medicinal value and typically grows on euphorbia without harming it.
“It has strong medicinal properties for humans and animals. It was used to cure chicken coccidiosis,” said Prof. Amutabi, whose research was published about a decade ago on www.taylorfrancis.com.
He added that a biochemistry student from an American university had made significant findings on dodder, discovering its strong antibiotic properties.
“The plant is undergoing efficacy trials by a team of scientists from TUK, and I’m sure they will share their findings,” said Prof. Amutabi.
In 2020, the Kenya Forestry Research Institute (KEFRI) published guidelines for dodder management, describing it as having slender, twining stems that vary from pale green to yellow or bright orange, easily seen against the host plant’s foliage.
“The genus Cuscuta is found throughout temperate and tropical regions, with the greatest species diversity in subtropical and tropical areas,” the guidelines co-authored by KEFRI researchers say.
Dodders are prolific seed producers, with each plant capable of producing several thousand seeds per season.
“While only about 5% of the seed germinates the year after production, the remaining seeds can remain dormant in the soil for over 20 years, depending on the species and environmental conditions,” the researchers noted.
KEFRI warns that if left uncontrolled, dodder could cause serious food security threats by 2029.
“The rapid spread and wide host range suggest dodder may threaten the sustainability of many crops, shrubs, and trees if unmanaged. Agricultural yield losses could be significant by 2029,” KEFRI said.
An article titled Dodder, a Parasitic Vine Weed, published on www.ecolandscaping.org, defines parasitic plants as those that derive nutrients from other plants and cannot photosynthesise.
The article recommends pulling out vines before they flower and monitoring affected plants to ensure continued dodder removal.
Research shows dodder seeds are often spread as contaminants in sugar beet, clover, alfalfa, and flaxseed, as well as by animals, contaminated soil on tools, and ploughs.
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“If left unchecked, dodder will spread further each year, producing seeds that contaminate the soil seed bank,” KEFRI reported.
According to KEFRI, four herbicides (Gramoxone 200 SL, Agrimine 2-4D, Willosate 360 SL, and Herbikill 20SL) have been identified to manage dodder.
The research agency emphasises the need to sensitise the public against transporting dodder as an ornamental plant and advises immediate destruction and burning of the parasite’s stems.
