The invasive plant giving farmers sleepless nights

Kenyatta University biotechnologist, Willy Kibet examines a plant infested with the Japanese dodder. The Kenya Plant Health Inspectorate (Kephis) terms Japanese dodder as the most destructive weed, with researchers saying it is heightening apprehension among farmers as it attacks and kills both trees and crops. PHOTO | PIUS MAUNDU | NMG

What you need to know:

  • The parasitic plant Japanese dodder is spreading across the country faster as it attacks trees and crops suffocating them to death.
  • The weed has become the latest threat and source of headache to farmers across the country, thanks to its invasive nature.
  • The Kenya Plant Health Inspectorate (Kephis) terms Japanese dodder as the most destructive weed, with researchers saying it is heightening apprehension among farmers as it attacks and kills trees and crops.
  • Online reports show that the dodder is native of Asia, where some of its species are used to make herbal medicine, but no one knows how it entered the country.

Sometime in June last year, Dorothy Katilo, a farmer in Makueni, walked home in high spirits after she landed from a neighbour a handful of vines from a plant known as Japanese dodder (Cuscuta japonica).

She was happy because the plant at the neighbour’s home had formed an enviable canopy atop trees under which visitors sheltered.

“I was impressed by the spectacular canopies atop her yellow oleander trees that I picked the vine and planted in my compound,” she recounted.

When Seeds of Gold met Dorothy at her Kyumu village last week, she was an unhappy farmer as she was cutting down her orange trees after the parasitic plant colonised them.

“The weed spread from near the tree where I planted it into my orchard where they suffocated my orange and pixie trees. Some have withered and died. Each orange tree offers me three sacks of fruits annually,” said Katilo, noting planting the vine is one of the worst things she has ever done.

After cutting the affected plant, she supervised the burning of the twigs as she tried to control the invasive plant that has baffled scientists and farmers.

The weed has become the latest threat and source of headache to farmers across the country, thanks to its invasive nature.

It joins fall armyworms, lethal necrosis disease and tuta absoluta, the first two which ravage maize and the last, tomato crops.

Dodder’s many other names include love vine, knot weed, strangleweed, stranglevine, angel’s hair, goldthread, devil’s ringlet, hell-bind, hairweed, devil’s hair, hailweed and witches’ shoelaces.

The weed builds a canopy on the host tree or plant and casts thousands of tendrils to form a dense spectacle before it strangles it to death.

MOST DESTRUCTIVE WEED

The Kenya Plant Health Inspectorate (Kephis) terms Japanese dodder as the most destructive weed, with researchers saying it is heightening apprehension among farmers as it attacks and kills trees and crops.

Asenath Koech, a plant pest specialist at Kephis, told Seeds of Gold that the agency is concerned at the speed at which the parasitic plant is spreading across the country.

Its rapid spread is partly facilitated by its floral appeal, the ignorance of farmers and lack of tried and tested scientific control mechanisms.

Dorothy Katilo, a farmer in Makueni uses a machete to cut the weed which has infested her farm. The weed has become the latest threat and source of headache to farmers across the country, thanks to its invasive nature. PHOTO | PIUS MAUNDU | NMG

It has drawn the interest of scientists, who have established that besides trees and hedges, dodder attacks mangoes, tobacco, citrus plants, tea and coffee bushes.

“It also attacks tomatoes and beans as well and there are reports that it has destroyed acres of these crops in days in a neighbouring country,” said Dr Steven Runo, a molecular biologist and a specialist in parasitic plants.

Dr Runo, a senior lecturer at Kenyatta University, has since January been leading a team of scientists in studying the weed.

“Once dodder attacks a plant, it rapidly spreads out while infusing itself into the host through multiple special nodes, which it uses to suck water and nutrients weakening the victim and eventually killing it,” he explained.

Japanese dodder, according to him, normally penetrates the host by puncturing the vascular tissue at several points through which it sucks water and nutrients leaving the host withering.

Dr Runo is convinced that the weed kills its host by injecting a poisonous substance.

“Some farmers in western Kenya are calling this weed ‘the HIV of plants’ and we concur because it is highly invasive. It gradually kills its host and has no known cure at least in the meantime,” he told Seeds of Gold.

Though its tendrils are green and form a beautiful canopy, the plant that spreads in record time cannot make its own food through photosynthesis, according to Dr Runo.

“That is why it parasitises domesticated and wild plants, use their nutrients to thrive, weakening the host plant, and, eventually, killing them.”

CLIMATE-CHANGE RELATED INVASION

Online reports show that the dodder is native of Asia, where some of its species are used to make herbal medicine, but no one knows how it entered the country.

Scientists believe the dreaded weed entered the country from the neighbouring nations. Dr Runo’s team is studying the genetic footprint of the parasitic plant to understand how it entered the country.

The flowering plant produces seeds, which come packaged in light capsules that are easily spread by wind.

Kipkorir Lagat, a farmer in Nandi points at the invasive weed which has now colonised his farm. The dodder parasite is spread by human or animal activity. It germinates anywhere and its seeds are believed to live in the soil for up to 10 years. PHOTO | STANLEY KIMUGE | NMG

Dodder, according to him, compares with the dreaded striga, which is commonly known as witchweed because it suffocates maize and sorghum by strangling their roots, grows through both the seeds and from vines.

Koech said at least 12 counties, mostly in Eastern, Western and the Rift Valley, are affected by the weed and calls agriculture extension officers to help sensitise farmers on ways of managing and controlling it.

Maseno University’s Department of Agriculture Head, Prof Matthew Dida, said that there are different kinds of Japanese dodder species, which affect the indigenous vegetables and trees.

“The parasitic plant can evolve to affect other species that they traditionally didn’t. The most affected tree species currently is the yellow oleander,” said Prof Dida.

The dodder parasite is spread by human or animal activity. It germinates anywhere and its seeds are believed to live in the soil for up to 10 years.

“This is a climate-change related invasion because dodder is now finding home places where it never did before,” said Mary Mbenge, the chief officer at the Department of Environment and Climate Change at Makueni County.

She noted that the weed has invaded Mbooni, Kaiti, Kibwezi, Kilome and Makueni. She has started a campaign to mechanically remove and burn the weed from trees in the county. She blames ignorance among the masses for the rapid spread of the weed in the county and elsewhere.

“Some people spread the weed when they propagate it at their homes thinking that it is a flower. This should stop,” she told Seeds of Gold as she led a team of government officials in removing the weed from the hedges of Makueni County Referral Hospital, one of the many places the weed has colonised in the county.

BURNT TO AVOID SPREADING

Jared Mutai, the deputy director of agriculture in-charge of horticultural crops in Nandi, noted that some farmers in the county have complained that the weed had dried their tea.

According to him, permanent crops like coffee, avocado and tea are under threat from the weed. “There are no much control measures except to manually prune the weed, which sometimes may be difficult,” said Mutai.

Trans Nzoia Agriculture executive Mary Nzomo said the weed had been reported in the region and that a team from Centre for Agriculture and Bioscience International (CABI) did a survey to ascertain its impact on food security.

Dorothy Katilo's mangoes which have also fallen victim to the invasive parasitic Cuscuta japonica. The weed normally penetrates the host by puncturing the vascular tissue at several points through which it sucks water and nutrients leaving the host withering. PHOTO | PIUS MAUNDU | NMG

“The survey was just concluded and its report will reveal the host range of crops it is colonising after which we will determine whether it is threat to food security. Currently, it is commonly seen on the hedges,” explained Nzomo.

Mechanical removal of dodder vines or pruning the affected sections of affected plants is one of the methods of managing it, which Kephis recommends.

“The vines should be removed before the flowering stage and burnt to avoid spreading to other plants,” said Koech.

Farmers should also avoid plants that are liked by the weed like oleander and instead grow those that the weed does not like much.

Koech discourages the picking of vines in areas where the parasitic weed exists to stem further spreading.

-Additional reporting by Stanley Kimuge and Elizabeth Ojina.

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Cows and goats feed on the weed

Kipkorir Lagat, a farmer in Nandi, recounted that when the weed was reported in the area, some thought it was edible like wild vegetables.

“But we realised it had no leaves. Cows and goats feed on it and we want research to be conducted so that we know if is beneficial or not,” says Lagat.

“We are losing so many trees due to this weed. If we won’t stop it then the rivers will dry up,” he adds.

Vegetative spread of dodder can occur through the extensive growth of stems, which can reach up to five meters in just two months, but regeneration can also occur from stem fragments.