Tomato plant infected with Tomato Yellow Leaf Curl. Note upward and inward rolling of the leaf margins.
(c) Ian D. Bedford. Reproduced from the Crop Protection Compendium, 2005 Edition. CAB International Publishing, Wallingford.
Whiteflies cause direct damage to plants by sucking plant sap and removing plant nutrients, thereby weakening the plants. Damage may be more severe when plants are under water stress. In addition, they often produce large quantity of honeydew that leads to the growth of sooty mould on the lower leaves, blocking or reducing the photosynthetic capacity of the plants. The honeydew also contaminates the marketable part of the plant, reducing its market value or making it outright unsaleable. Infested plants may wilt; turn yellow in colour, become stunted or die when whitefly infestations are severe or of long duration.
Whiteflies are also serious indirect pests as vectors of virus diseases. Bemisia tabaci transmits serious virus diseases on cassava, cotton, tobacco, tomato, beans, chillies, and sweet potatoes. Whitefly transmitted viruses are among the most serious virus diseases on plants; Virus infection often results in total crop losses. This whitefly is the vector of a range of leaf curl disease-inducing virus, in Eastern and Southern Africa, including Tomato Yellow Leaf Curl Virus, the African Cassava Mosaic Virus, Cowpea Mild Mottle Virus, Watermelon Chlorotic Stunt Virus among others.
The African Cassava Mosaic Virus is one of the most important factors limiting cassava production in Africa. In sweet potatoes B. tabaci transmits the Sweet potato Chlorotic Stunt virus, which together with the aphid-transmitted Sweet potato Feathery Mottle Virus causes the Sweet potato virus Disease, the most important disease constraint to sweet potato production in Sub-Saharan Africa (Legg et al., 2003).
Major species of whiteflies in Africa:
- The greenhouse whitefly (Trialeurodes vaporariorum)
- The tobacco whitefly or sweet potato whitefly (Bemisia tabaci)
- The spiralling whitefly (Aleurodicus dispersus)
- The citrus woolly whitefly (Aleurothrixus floccosus)
- The cabbage whitefly (Aleyrodes proletella)
For more information on whiteflies on different crops click on the crop name:
The tobacco whitefly (Bemisia tabaci) and the greenhouse whitefly (Trialeurodes vaporariorum) attack a very wide range of wild and cultivated plants. Bemisia tabaci is the dominating whitefly in the region. Its host range includes cotton, tobacco, vegetables (tomatoes, eggplant, okra, bell peppers, cucurbits, etc.), legumes (beans, soybeans, cowpeas and groundnut), tuber and root crops (sweet potato, cassava, potato) among others. The host range of Trialeurodes vaporariourm is similar to the one for Bemisia tabaci, but the former usually occurs at higher altitudes and cooler climates than B.tabaci. Trialeurodes vaporariorum attacks many plants grown under protected conditions (greenhouses) in temperate countries, the most severely affected crops are aubergine, cucumber, beans, sweet peppers, tomatoes and a large number of ornamentals. The status of this whitefly in field grown crops in the region is not clear.
The cabbage whitefly (Aleyrodes proletella) is a pest of Brassicas but rarely reaches levels that require intervention.
The citrus woolly whitefly (Aleurothrixus floccosus) is found mainly on citrus plants, but also attacks coffee (arabica), guava, eggplant, aubergine, mango, and several wild plants.
The spiralling whitefly (Aleurodicus dispersus) feed on many plants. In West Africa, it has been observed causing damage on many food crops, including cassava, soybean, pigeon pea, citrus, papaya and others. This whitefly has also been recently found in East Africa.
Feeding of whiteflies causes yellowing of infested leaves. Whiteflies excrete honeydew, a clear, sugary liquid. This honeydew covers the lower leaves and supports the growth of black sooty mould, which may coat the entire plant. Where plant viruses are transmitted plants show the typical symptoms of the virus diseases. Presence of whiteflies can also be recognised by a cloud of tiny whiteflies flying up when the plants are shaken. The whiteflies resettle soon on the plants.
Affected plant stages
Seedling, vegetative growing and flowering stage
Affected plant parts
Leaves: honeydew or sooty mould.