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Invasive alien species in Kenya: status and management

Chagema Kedera and Benson Kuria

Kenya Plant Health Inspectorate Service, P.O. Box 49592, Nairobi, Kenya; e-mail:


Kenya has had several invasions of alien species that have had negative impacts on biodiversity, agriculture and human development. Studies show that Kenya has been invaded by 34 species: 11 arthropods, ten microorganisms, nine plant species and four vertebrates. Management strategies have included quarantine measures for unintentional and intentional introductions, eradication, containment and control, monitoring and research, regional cooperation and public awareness. More cooperation, assistance and capacity building is required to effectively manage the problem of invasive species.


Kenya has experienced a number of biological invasions, some of which have had significant consequences on socio-economic status (Keil, 1988). Notable examples include the larger grain borer (Prostephanus truncatus) (Hodges et al., 1983; Muhihu and Kibata, 1985), the water hyacinth (Eichhornia crassipes) (Hill, Cock and Howard, 1999) and Prosopis spp. Available information on invasive species in the East African region shows that some 34 different species have invaded Kenya (Farrell, Kibata and Sutherland, 1995; Lyons, 2000; Kibata, G.N., pers. comm.). Table 1 lists these 11 arthropods, ten microorganisms, nine plants and four vertebrates, and outlines their impacts. Few of these species are under control, hence the concern. Various management strategies and activities have been used to address the problem of invasive alien species in Kenya.

Quarantine measures to prevent unintentional introductions

To prevent the introduction of invasive alien species into Kenya, importation of any plant material is subject to strict specified conditions. The stipulated procedures ensure that enough information on the plant material is available to evaluate the pest risk of potential invasives. Plant quarantine restrictions are based on pest risk analysis and existing scientific knowledge on the distribution, biology and pests of the plant. Suitable regulations are enforced to facilitate the import and export of plant materials through the issuance of import permits and phytosanitary certificates. Legal authority is provided to allow for treatment or destruction of infested or infected plants or plant products.

Inspections are carried out at the entry points (i.e. international airport, sea ports and borders) to enforce quarantine measures. The border control points are located where there is a risk of entry of alien species (see figure 1). Most are located in the southern and western borders of Kenya because there is considerable trade and movement of plant materials between Kenya and Uganda and Tanzania. There is no significant movement of plant materials in most of Kenya’s northern and northeastern borders (i.e. from Ethiopia and Somalia). Most of this region is arid.

Table 1: Invasive species recorded in Kenya.


Year of arrival

Impact on native plants, animals and ecosystems

Impact on humans (livelihood, transport, health etc.)

1. Arthropods

Larger grain borer
Prostephanus truncatus


Pest of stored maize and cassava

Heavy post-harvest losses in maize; trade restrictions

Serpentine leafminer
Liriomyza trifolii (Burgess)


Pest of many horticultural crops

Crop losses and loss of overseas markets due to quarantine requirements

Western flower thrips
Frankliniella occidentalis


Pest of many flower crops, pulses and horticultural crops

Intensified use of pesticides; loss of crop and capital due to quarantine requirements

Cypress aphid
Cinara cupressivora


Cypress trees decimated

Degraded environment

Russian aphid
Diuraphis noxia


Barley and wheat production reduced

Less food, income available

Cassava mealybug
Phenacoccus manihoti


Reduced cassava production

Less food, income available

Leucaena psyllid
Heteropsylla cubana


Reduced fodder

Loss of capital

Citrus woolly whitefly
Aleurothrixus floccosus


Reduced fruit production

Loss of capital

Purple tea mite
Calacarus carinatus


Reduction in tea leaf production

Loss of capital

Tomato russet mite
Aculops lycopersici


Reduced tomato production

Loss of capital

Louisiana crayfish
Procambarus clarkii


Reduction of flora and fauna, increased turbidity

Harvested by man

2. Micro-organisms

Crown gall
Agrobacterium tumefaciens


Reduced production in roses

Loss of capital

Black Sigatoka
Mycosphaerella fijiensis


Reduced banana production

Less food, income available

Panama disease Fusarium oxysporum f. sp. cubense


Reduced banana production

Less food, income available

Cassava mosaic disease ACMV (UgV)


Reduced cassava production

Less food, income available

Maize streak disease (MSV)


Reduced maize production

Less food, income

Fruit and leaf spot
Phaeoramularia angolensis


Reduced citrus production

Less food, income

Citrus greening disease (bacterial)


Reduced citrus production

Less food, income

Barley yellow dwarf virus (BYDV)


Reduced barley and wheat production

Less food, income available

Napier grass smut
Ustilago kamerunensis


Reduced fodder production

Loss of capital

Coffee berry disease
Colletotrichum coffeanum


Reduced coffee production

Loss of capital

3. Plants

Water hyacinth
Eichhornia crassipes



Very serious

Water fern
Salvinia molesta




Prosopis spp.




Wild garlic
Allium vineale



Serious to horticultural farmers

Prickly pear
Opuntia spp.

1940s - 50s

Out-competes native plants, precludes grazing and browsing near it

Poisonous, spines dangerous

Mexican marigold
Tagetes minuta



Increased weed eradication costs

Lantana camara


Out-competes other vegetation

Poisonous to livestock, habitat for tsetse flies

Morning glory
Ipomoea spp.


Grows over and out-competes other plants

Reduced pasture

Eucalyptus spp.

1939 - 45

Minimal, though some evidence it retards recruitment of native species


4. Vertebrates

Nile perch
Lates niloticus


Greatly reduced abundance of native cichlids

Economic boost to fishers, reduced catch of smaller species

House sparrow
Passer domesticus

Early 1900s

Displacing local sparrows

Noisy, messes buildings with nests

Agapornis sp.

19th century

Competing with local species for nest holes

Pests especially for cereals

Indian house crow
Corvus splendens


Displacing native species, kills fruit bats

Urban pest, damages crops, hazard at airport

Fig. 1: Map of Kenya showing agroclimatic zones and points of entry where phytosanitary inspection is carried out.

Quarantine measures taken during intentional introduction of alien species

Intentional introduction of alien species in Kenya has been done under authority of the Kenya Standing Technical Committee on Imports and Exports, which is a body that approves importation of restricted and new materials into the country. The committee operates under the Plant Protection Act (Cap 324) of the laws of Kenya.

Most of the deliberately introduced alien species are biocontrol agents. An appropriate risk analysis is carried out as part of the authorization process before coming to a decision on whether or not to authorize a proposed introduction. A comprehensive dossier on the intended introduction is submitted for evaluation by the standing technical committee. Authorization of an introduction is accompanied by conditions such as containment requirements, monitoring procedures, preparation of mitigation plans.

Eradication, containment and control

For invasive species that have been unintentionally introduced to Kenya, appropriate steps such as eradication, containment and control have been undertaken to mitigate adverse effects. For instance, for water hyacinth control, options have included mechanical removal of the weed and the use of biocontrol agents. Enforcement of domestic quarantine has been done, such as when the larger grain borer was first detected. Monitoring was also carried out in other susceptible areas to detect invasion and hence put in place appropriate control measures.

Research and monitoring of alien invasive species

Much research has been undertaken in Kenya to develop an adequate knowledge base to address the problem of invasive species (Farrell, Kibata and Sutherland, 1995). This has been especially so for serious invasive species such as the larger grain borer, the water hyacinth and Prosopis spp. Research has been undertaken by national research institutes such as the Kenya Agricultural Research Institute and Kenya Forestry Research Institute. Studies have included the biology and ecology of the invasive species (Nang’ayo et al., 1993), history and ecology of invasion and associated impacts on the ecosystem, species and socio-economic impacts. The Kenya Plant Health Inspectorate Service (KEPHIS), as the national plant protection organization in Kenya, has worked closely with the research institutions to determine the status of invasive species and develop management options.

Monitoring has also been done to detect new invasive species. Monitoring has involved institutions such as Kenya Agricultural Research Institute, the International Centre of Insect Physiology and Ecology and KEPHIS. Monitoring has been carried out for species such as larger grain borer, fruit flies and water hyacinth. Quarantine surveillance has also been done to detect new species.

Regional and international cooperation

There is a need for a regional approach to address the issue of invasive species because some of the species affect different countries. Examples include the water hyacinth, which has affected Kenya, Tanzania and Uganda, and the larger grain borer, which has severely affected Kenya and Tanzania (Hodges et al., 1983). To this end, there has been a move towards regional cooperation between the three East African states and harmonization of phytosanitary measures among the different countries. Strengthening of phytosanitary services, inspection and certification has also been done. This has played a big role in the prevention and control of invasive species.

On the international front, Kenya is a contracting party to the International Plant Protection Convention, whose purpose is to secure a common and effective action to prevent the spread and introduction of pests of plants and to promote appropriate measures for their control.

Capacity building

With assistance from the Food and Agriculture Organization of the United Nations, training of staff has been undertaken to make Officers aware of contemporary phytosanitary issues and ensure that they effectively implement phytosanitary measures. Staff have also been trained on specific phytosanitary issues such as pest risk analysis and identification of pests of quarantine importance.

Additionally, efforts have been made to strengthen phytosanitary activities within KEPHIS. These have included:

Education and public awareness

KEPHIS has striven to raise public awareness on phytosanitary issues and invasive species. This has been important in preventing the introduction and management of invasive species. Public awareness activities have included:


Kenya, like many other countries, is faced with the problem of managing invasive species that have caused socio-economic losses. The country has put in place several measures to mitigate the impacts of the invasive species. However, more cooperation, capacity building and assistance is needed to manage effectively the problem of invasive alien species.


Farrell, G., Kibata, G.N. & Sutherland, J.A., eds. 1995. A review of crop protection research in Kenya. KARI/ODA Crop Protection Project. Nairobi, Kenya, Kenya Agricultural Research Institute. 165 pp.

Hill, G., Cock, M., & Howard, G. 1999. Water hyacinth, its control and utilisation: a global review. CABI Bioscience and IUCN. Publications on Water Resources: No. 15. Stockholm, Sweden, Swedish International Development Cooperation Agency (SIDA). 54 pp.

Hodges, R.J., Dunstan, W.R., Magazini, I.A. & Golob, P. 1983. An outbreak of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) in East Africa. Protection Ecology, 5: 183 - 194.

Keil, H. 1988. Losses caused by the larger grain borer in farm stored maize. In: G.G.M. Schulten & A.J. Toet, eds. Workshop on the containment and control of the larger grain borer, Arusha, Tanzania, 16-21 May 1988, pp 28 - 52. Rome, Italy, FAO. ii + 209 pp.

Lyons, E.E. 2000. Preliminary survey of invasive species in Eastern Africa. In: E.E. Lyons & S.E. Miller, eds. Invasive species in Eastern Africa: Proceedings of a workshop held at ICIPE, July 5 - 6, 1999, pp. 65 - 70. Nairobi, Kenya, International Centre of Insect Physiology and Ecology (ICIPE) Science Press. 108 pp.

Muhihu, S.K. & Kibata, G.N. 1985. Developing a control programme to combat an outbreak of Prostephanus truncatus Horn (Coleoptera: Bostrichidae) in Kenya. Tropical Science, 25: 239 - 248.

Nang’ayo, F.L.O., Hill, M.G., Chandi, E.A., Chiro, C.T., Nzeve, D.N. & Obiero, J. 1993. The natural environment as a reservoir for the larger grain borer Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) in Kenya. African Crop Science Journal, 1: 39 - 47.

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