Lantana: The silent cattle killer weed

The invasive lantana weed that has encroached in parts of the forest. PHOTO: JECKONIA OTIENO

It is grown as a hedge plant on live fences or interfaced within range lands to be browsed by ruminants. But many farmers don’t know that lantana camara is a poisonous weed that can kill both man and cattle.

Lantana Camara, or lantana as it is commonly referred to, is a highly invasive shrub thought to have been brought into Africa from Europe.

The plant has permeated the continent with disastrous effects as a poisonous weed, although many still treat it as cattle feed when it is actually a poisonous weed.

There are more than 50 varieties of this weed that has beautifully coloured flowers. This has endeared them as ornamental plants in many home gardens.

Unfortunately, many farmers, gardeners and home owners are oblivious of the negative effects this plant can have on their children, cattle and the environment at large. When consumed, unripe lantana seeds have been reported to cause death due to nervous or circulatory malfunctions.

Aggressive invader

Lantana propagates itself both by cuttings and seeds. The seeds can still further propagate asexually and can withstand digestive enzymes of most animals.

They are spread by birds, rodents, animals and human beings.

Lantana grows on a wide range of soils, making it easy to spread. It was introduced in Kenya in the 1950s.

Its presence in every corner of the country attests to its aggressive invasion. The weed is the most widespread terrestrial invasive plant in tropics and sub-tropics. It is listed among the world’s top 10 worst weeds.

The gardening industry is worsening its spread through propagation of lantana varieties as ornamental plants in residential areas, an activity that will worsen the problem in near future.

Lantana shrubs are slowly taking over large grazing areas as many people consider it a friendly plant. Studies show that lantana leaves have a chemical which kills any other plant in its vicinity.

A closer look at lantana shrubs will reveal a bare ground underneath the bushes. This is a way of reducing competition for nutrients as the plant perpetuates its colony. Lantana can quickly outgrow other plants in search of sunlight, but even when overgrown by other plants, it will still grow in shade conditions unlike many other plants. Vegetation clearance through burning has been shown to discourage re-growth of other plant species but encourages re-growth of lantana.

Lantana caused diseases

Lantana has chemicals that destroy the liver. Once it destroys this key body organ, the animal will begin to show signs of sensitivity to sunlight. This condition is known as photosensitivity and is common in body parts with little hair cover.

Such parts include areas around the eyes, nose, mouth, ears and udder. When lesions occur on the udder, it leads to reduced milk production.

In areas surrounding the mouth, lantana lesions may cause difficulty in grazing and eventual loss of appetite, thus reduced productivity. The skin in affected areas will swell, form crusts and are itchy – the animal will rub itself against rough surfaces, resulting in open wounds and subsequent secondary infections.

Other health consequences in cattle as a result of liver damage include ill health and slow growth.

If the disease is diagnosed early, the animal should be removed from the incriminate feed. Anti-inflammatory drugs can be used at this stage. When the condition progresses and secondary bacterial infections set in, anti-microbials are recommended.

Unfortunately, most farmers and clinicians may not be aware of the causative weed. The farmer may either continue exposing the cattle to lantana or treating the condition inappropriately. Lantana also destroys kidneys and cattle continually exposed to its poison can die.

Losses caused by lantana

Apart from causing losses to farmers due to veterinary costs and reduced livestock productivity, lantana camara also reduces the size of grazing lands as it kills pastures. Loss of production due to lantana remains largely undocumented and thus unknown.

How to control killer weed

Public awareness on negative effects of lantana on cattle keeping and the environment should be the first step in its control and eventual eradication.

This awareness should include gardeners and home owners who are using variants of the plant to decorate their homesteads of its poisonous unripe berries and its invasive traits.

Lantana is yet to be listed as a noxious weed in East Africa. But even in countries like South Africa where it is listed as a noxious weed and efforts put in place to eradicate it, much is yet to be achieved.

Elimination of lantana requires early detection and rapid removal. Use of herbicides in control of lantana is the most effective method.

The writer is a veterinary surgeon working with the Kenya Tsetse and Trypanosomiasis Eradication Council - Kenttec