Have you seen this invasive, colourful vine that wraps itself around plants, from flower hedges to trees and cash crops? Maybe you’ve touched or broken its vine out of curiosity to see how it feels? Did you know that for some species, breaking the vine actually helps it spread by creating new plants?
This parasitic weed is the Cuscuta species, and it can endanger your crops. It is commonly known as Devil’s Hair Weed or dodder. Other names include devil’s ringlet, devil’s guts, gold-thread, hail-weed, hair-weed, hellbine, love vine, strangle-weed, and witch’s hair. In Kenya, the Kikuyu native language refers to it as thina, directly translated to mean poverty because when it strikes your farm, there is hardly any crop left to gain from.
There are over 150 species of dodder.
“Dodder is a true vegetal vampire. With its fine stems it sticks to its victims, then literally sucks the sap until it kills the host.” (Pamplona-Roger, 2000). Because of its feeding habit, this plant poses a huge threat to farming and agriculture in the continent.
If you are looking for ways to remove dodder from your farm, garden, or trees, then read on.
Identification
This parasitic weed has a distinctive appearance and is known for its thin, thread-like stems that range in colour from yellow to orange or sometimes pale green. These stringlike or wiry, leafless vines wrap tightly around host plants, creating a tangled web-like mass. Lacking roots and leaves, Devil’s Hair relies entirely on its host for nutrients and water, embedding specialised structures called haustoria into the host plant’s vascular system.
From a distance, it often appears as a colourful but ominous tangle draped over affected plants. This weed poses a significant threat to agricultural crops and natural ecosystems as it can infect a wide range of crops and reduce both yield and quality.
It affects plants at every growth stage, from seedlings to vegetative growth, flowering, and fruiting. The affected parts include the entire plant, as well as the leaves and fruits or pods.
Devil’s Hair does not produce leaves or roots in the typical sense, relying entirely on its host plants for survival. Unlike the root parasites Striga and Orobanche, Cuscuta species do not require a germination stimulant provided by host roots. Dodder seeds sprout at or near the surface of the soil. While dodder germination can occur without a host, it has to reach a green plant quickly, normally within 5-10 days after germination. Dodder grows toward the smell of nearby plants.
An interesting fact about this plant is that the seedling has only a rudimentary root for anchorage, while the shoot circumnutates, that is swings round anti-clockwise about once per hour until it makes contact with any stem or leaf, around which it will coil before growing on to make further contacts. After a dodder attaches itself to a plant, it wraps itself around it. If the host contains food beneficial to dodder, it produces haustoria (root-like growths) that insert themselves into the vascular system (water and nutrient conducting tissues) of the host.
The haustoria have three functions: attachment, penetration of the host stems, and nutrient acquisition from the host. After successful attachment to a suitable host, the original root of the dodder in the soil dies. Without a host, Cuscuta will die within a few days.
The dodder can grow and attach itself to multiple plants. In tropical areas it can grow more or less continuously, and may reach high into the canopy of shrubs and trees. In temperate regions, it is an annual plant and is restricted to relatively low vegetation that can be reached by new seedlings each spring.
Early identification is key to controlling Devil’s Hair. The yellow to orange threads wrapping around a host plant are an immediate indicator. Farmers should look for signs of wilting, stunted growth, or weakened plants surrounded by the characteristic tangled stems of Cuscuta. Leaves of infested plants will turn yellow and eventually die. Severely infested plants wilt and die. Early detection allows for more effective control methods, especially before the weed has a chance to produce seeds.
How Devil’s Hair Spreads
The spread of this weed is facilitated by its unique lifecycle and small, resilient seeds. A single Cuscuta plant can produce thousands of tiny seeds that disperse through various methods, including wind, water, animals, and contaminated farming equipment. Ninety-five per cent of these seeds can remain viable in the soil for 5-10 years, germinating when they detect nearby host plants. Once the seedling detects a host, it attaches itself, creating a self-sustaining cycle of infestation. Without prompt intervention, Devil’s Hair can quickly overtake a field, spreading to neighbouring plants and even farms.
Dodder seed can also be spread by irrigation water, in the manure of livestock that has fed on infested plants along with the seed of dodder, and also through movement of contaminated seed of crops, for example lucerne or onion. Many dodder species also propagate vegetatively through tiny stem cuttings that can be spread by vectors like birds, animals or humans. Water surface run-off is also a known spreading mode carrying seeds and vines from infected to non-infected areas.
The above methods of spreading make control of the weed difficult for farmers as one cannot control some vectors like birds in open field farming. Another contributing factor is failure to observe field hygiene such as use of infested tools, composting and improper disposal of infected material, mud attached to tyres or shoes, etc.
Impact on Agriculture
Devil’s Hair is particularly dangerous for a wide variety of crops, including legumes, vegetables, and ornamentals. Once it attaches to a crop, it can severely reduce yields, stunt plant growth, and even cause death in some cases. The weed spreads easily, with seeds being dispersed by wind, water, animals, or contaminated farming equipment. Moreover, due to its parasitic nature, it is difficult to control using traditional weeding methods.
Control Methods
1. Cultural Control
Prevention is the best approach when it comes to Cuscuta. Crop rotation with non-host plants like grasses can help break the life cycle of the parasite. Using certified, clean seeds can also prevent the introduction of dodder into fields. Maintaining a healthy, dense crop stand can make it harder for Cuscuta to establish itself. The aim is to control before dodder sets seed by collection and deep burying of infested plants. This may have to be done repeatedly throughout the growing season as dodder seed germinates from the upper 3cm of the soil. Prevent livestock from grazing infested areas after dodder has set seed, and do not allow livestock that have grazed fields where dodder has set seed to move to other areas.
2. Mechanical Control
Early detection and removal of infected plants are crucial. Once Cuscuta has attached itself to a plant, manual removal of both the host and the weed may be necessary. Mowing or cutting Cuscuta infested areas before it has a chance to spread its seeds can help reduce future infestations. Hand-pulling is suitable only for scattered infestations as the infested crop plants have to be removed with the parasite. Scattered infestations can also be controlled by heat, using a hand-held flame gun. More extensive infestations in lucerne are also sometimes treated with overall flaming, as the crop is able to recover. The removed parts should then be burned or buried deep in the soil to avoid future germination.
3. Chemical Control
Chemical herbicides can be used to manage Cuscuta infestations, although timing is critical. Pre-emergence herbicides can be effective in preventing the weed from establishing. Post-emergent control is more difficult, as Cuscuta is often attached to crops, and non-selective herbicides can damage both the parasite and the host plant. Specific contact herbicides can be applied carefully to target the parasite without severely affecting the host plant.
4. Biological Control
Research into biological control agents, such as insects and pathogens that target Cuscuta, is ongoing. In some regions, promising results have been seen with the introduction of certain insect species that feed on the parasitic weed, although this method is not yet widely available.
5. Integrated Control
Integrated methods involve the all-important use of clean seed; good field hygiene to eradicate scattered infestations before they get out of control; good control of other weeds which might act as reservoirs of infestation; timing of tillage and planting to maximise destruction of parasite seedlings before sowing; and optimum planting arrangement and growing conditions for a good crop canopy to suppress development of the weed.
Prevention and Management
Farmers can prevent the spread of Devil’s Hair by regularly inspecting their fields and promptly removing any infestations before they spread. Proper sanitation of farm tools, machinery, and boots is also important to prevent the transfer of seeds between fields. Introducing trap crops (plants that attract Cuscuta but do not support its growth) can also serve as a method to reduce infestations over time.
Farmers should always plant clean certified seed as many nations have laws prohibiting import of dodder seed, requiring crop seeds to be free of dodder seed contamination (Phytosanitory regulations). Removal of highly favoured hosts such as bindweed Convolvulus arvensis from around field edges is also recommended. Other preventative measures farmers can take include:
- Tilling the land repeatedly to kill germinating dodder seedlings.
- Delay sowing of crops by 2-3 weeks after tillage to ensure that there are no suitable hosts for dodder attachment.
- Mow and weed early to destroy potential suitable hosts for dodder.
- Frequent monitoring of your farm for early detection and timely management of the weed.
Devil’s Hair Weed (Cuscuta spp.) is a significant challenge for farmers due to its parasitic nature and ability to spread quickly. Controlling this weed requires a combination of cultural, mechanical, and chemical methods to protect crops from severe yield losses. Farmers must remain vigilant and employ integrated weed management strategies to combat this invasive pest effectively. By addressing Cuscuta infestations early and applying sustainable agricultural practices, farmers can protect their crops and ensure long-term productivity while minimising the impact of this parasitic weed on food security.
