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Project News 06.2004

A new whitefly species emerges as
a pest of cereals in Central America

Projects :: Whiteflies as pests in tropical highlands
:: Whiteflies as virus vectors in mixed cropping systems
:: Whiteflies as vectors and pests in cassava

Whiteflies as vectors of viruses in vegetable and legume mixed cropping systems in East Africa

Geographical focus :: Sudan, Kenya, Uganda, Tanzania Start date :: January 1, 1997
Completion date :: December 31, 2000
 
Project Name :: Sustainable Integrated Management of Whiteflies as Pests and Vectors of Plant Viruses in the Tropics
Project Leader :: Dr. Pamela Anderson
Subproject Name :: Whiteflies as vectors of viruses in vegetable and legume mixed cropping systems in East Africa

Subproject Description ::





The highlands of eastern and central Africa constitute approximately 23% of the total land mass of the region. The area is densely populated and is currently home to more than 100 million people (approximately 51% of the total population) and is also the major source of water for northern, eastern and central Africa. The highlands provide 50% of the food value for the region, making a major contribution to the countries' GDPs. They support diverse land uses and economic opportunities; in addition to food for domestic consumption, coffee, tea, pyrethrum and horticultural crops are largely grown in the highland areas and are a major source of foreign exchange for the countries in the region.

The problem of whitefly-transmitted viruses on vegetables which is seen in Central America, Mexico and the Caribbean is beginning to emerge in Eastern African.

Bemisia tabaci is known to infest the more common vegetable crops in the subregion: tomatoes (Lycopersicon esculentum), eggplant (Solanum melongena), okra (Abelmoschus esculentus) and chillies (Capsicum annum). The legume crops which are commonly grown in association with vegetables in the subregion include bean (Phaseolus vulgaris), cowpea (Vigna unguiculata) and groundnut (Arachis hypogaea). Until recently, whiteflies were known to be minor or occasional pests on legumes. However, the trend in Sudan indicates that whiteflies are becoming an important pest on beans.

Tomato is one of the most widely cultivated vegetable crops in the region. Production is predominantly by small-scale farmers for fresh consumption, and yields are generally low. Small farmers get yields of 20t/ha while commercial farmers get yields over 100t/ha. These low yields are due to production constraints, particularly arthropod pest and diseases (GTZ, 1995).

In October, 1995, 25 participants from Kenya, Mozambique, Tanzania, Uganda, Zambia and Zimbabwe met in a tomato planning workshop for South-eastern Africa. The workshop reviewed the past 15 years of research on tomato plant protection for each of the countries represented. Workshop participants defined criteria of an important disease or pest as: 1) high yield losses, 2) widespread distribution, 3) high incidence, and 4) frequent occurrence. Based on these criteria, Bemisia tabaci was identified as the third most important arthropod pest, after red spider mites and African bollworms (Table 4; Varela & Pekke, 1995).

The participants of the tomato planning workshop for East and Southern Africa, were unable to prioritize whitefly-transmitted viruses due to lack of information from most countries. However, they felt that there is a need to assess the importance of WTVs in the region (GTZ, 1995). The preliminary results of a survey of major vegetables in southern Africa indicate that Tomato yellow leaf curl virus (ToYLCV) is a very important tomato disease in Southern Africa (Nono-Womdim, pers. comm.). However, there is a lack of quantitative information on the distribution and extent of yield loss due to ToYLCV, and other WTVs, in the region across the target crops in vegetable and legume based cropping systems. There is a critical need for baseline information as a prerequisite for prioritizing and planning the strategies for sustainable pest management interventions.

Workshop participants could not prioritize the importance of viral diseases due to lack of information from most countries, with the exception of Tanzania where Bemisia tabaci, as a vector of Tomato yellow leaf curl virus (TYLCV) was considered the limiting factor for tomato production (GTZ, 1995). Subsequent survey work carried out by the AVRDC regional office in South-eastern Africa has ascertained that TYLCV is also a serious problem in Malawi and Zambia. And prior work conducted by INRA (France) also found TYLCV to be a threat to tomato production in the Sudan. All commercial varieties of tomatoes grown in South-eastern Africa are susceptible to TYLCV (R. Nono-Womdim, pers. comm.). Control of whiteflies is based on the use of chemicals.

Project Purpose :: To gather, generate and analyze, through scientific and grower networks, baseline data relevant to the diagnosis and characterization of whitefly and WTV problems in the tropics, in order to propose a sound research agenda for improved understanding of pest and disease dynamics, IPM development and IPM implementation.

Project Outputs ::

  • International network for whiteflies and WTVs in the tropics established
  • Socio-economic and environmental impact assessed
  • Epidemiological characterization initiated
  • Agronomic characterization initiated
  • Preliminary studies for Phase 2 conducted

Project Impact :: The immediate beneficiaries of Phase 1 of the Project will be a) IARC scientists, b) NARS scientists, c) small holder farmers, and d) donor agencies. Additional, indirect, beneficiaries will be the general community of whitefly and WTV scientists and government policy makers.

Project Leader :: Dr. Lisbeth Riis / International Center for Insect Physiology and Ecology - ICIPE
Donor Partner :: Danish International Development Agency - DANIDA
Partner institutions
and collaborating professionals ::

Kenya

International Center for Insect Physiology and Ecology - ICIPE
Mr. Bernhard Löhr
Dr. Mohamed Ali Bob
Ms. Rebecca Raini
Mr. Thomas Njuguna
Dr. Srinivasan Sithanantham

Kenya Agricultural Research Institute - KARI
Dr. Benjamin Odhiambo
Mr. Gilbert Kibata
Dr. Jason Ong'aro

Tanzania

Asian Vegetable Research and Development Center - AVRDC
Dr. M. L. Chadha
Dr. Remi Nono-Womdim

Sudan

University of Gezira. Plant Pathology Centre, Faculty of Agricultural Science
Dr. Gasim Dafalla

Agricultural Research Corporation - ARC
Mr. Musa Ahmed

Malawi

Bvumbwe Agricultural Research Station - BARS
Dr. Harriet Thindwa
Mr. Patrick Khonje

Dissemination Outputs ::  
Keywords :: Sudan; Kenya; Uganda; Tanzania; whiteflies (Bemisia tabaci); Tomato (Lycopersicon esculentum); Eggplant (Solanum melongena); Okra (Abelmoschus esculentus); Pepper (Capsicum annum); Bean (Phaseolus vulgaris); Cowpea (Vigna unguiculata); Tomato yellow leaf curl virus
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