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Whitefly and whitefly-borne viruses in the tropics : Building a ... - cgiar

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CMD or whiteflies. Among farmers who<br />

attempted to manage <strong>the</strong> <strong>whitefly</strong>/<br />

disease problem, <strong>the</strong> ma<strong>in</strong> practices<br />

used were selection of plant<strong>in</strong>g<br />

materials, application of wood ash,<br />

rogu<strong>in</strong>g <strong>and</strong> proper weed<strong>in</strong>g. Agronomic<br />

features were more important than<br />

pest/disease resistance as criteria for<br />

<strong>the</strong> selection of plant<strong>in</strong>g material. S<strong>in</strong>ce<br />

<strong>the</strong> most frequently cited sources of<br />

plant<strong>in</strong>g material were neighbours’ <strong>and</strong><br />

farmers’ own fields (Figure 4), adoption<br />

of appropriate strategies for select<strong>in</strong>g<br />

plant<strong>in</strong>g material would be expected to<br />

reduce <strong>the</strong> <strong>in</strong>cidence of CMD<br />

appreciably. About 53% of farmers<br />

rogued CMD affected plants, usually<br />

with<strong>in</strong> 3 months of plant<strong>in</strong>g. Most<br />

farmers (61%), however, rated rogu<strong>in</strong>g<br />

as partially effective, with only 4%<br />

consider<strong>in</strong>g it to be highly effective. In<br />

<strong>the</strong> choice of varieties, 25% of farmers<br />

cited “Agric” as <strong>the</strong> s<strong>in</strong>gle most<br />

commonly planted variety <strong>and</strong> <strong>in</strong>dicated<br />

that <strong>the</strong> choice was based on<br />

recommendations that it was resistant<br />

to CMD. O<strong>the</strong>r CMD-resistant varieties<br />

commonly recorded were TMS 30572,<br />

TMS 30001 <strong>and</strong> TMS 30555. No farmer<br />

used pesticides aga<strong>in</strong>st CMD <strong>and</strong> fewer<br />

than 2% of farmers used pesticides<br />

aga<strong>in</strong>st whiteflies.<br />

Neighbour<br />

Own farm<br />

Market<br />

Research<br />

Extension<br />

0 5 10 15 20 25 30 35 40<br />

Figure 4.<br />

Relative frequency (%) of plant<strong>in</strong>g<br />

material source<br />

Farmers’ sources of cassava plant<strong>in</strong>g<br />

material <strong>in</strong> Nigeria.<br />

38<br />

Conclusions<br />

In Nigeria, whilst <strong>in</strong>cidence of CMD is<br />

high, <strong>the</strong> economic impact of <strong>the</strong><br />

disease is believed to be only moderate,<br />

Whiteflies <strong>and</strong> <strong>Whitefly</strong>-<strong>borne</strong> Viruses <strong>in</strong> <strong>the</strong> Tropics<br />

based on <strong>the</strong> relatively mild symptoms<br />

that were observed <strong>in</strong> <strong>the</strong> survey. There<br />

is an obvious need, however, to obta<strong>in</strong><br />

yield loss data for <strong>the</strong> commonly grown<br />

varieties <strong>in</strong> order to make an accurate<br />

assessment of economic impact. In view<br />

of <strong>the</strong> overwhelm<strong>in</strong>g importance of<br />

cutt<strong>in</strong>g <strong>in</strong>fection, as compared with<br />

vector-<strong>borne</strong> <strong>in</strong>fection, <strong>in</strong> <strong>the</strong> spread of<br />

CMD, research <strong>and</strong> extension efforts on<br />

assur<strong>in</strong>g <strong>the</strong> health of plant<strong>in</strong>g material<br />

should be prioritized. The farmers’<br />

generally high level of awareness of<br />

CMD <strong>and</strong> <strong>the</strong>ir will<strong>in</strong>gness to rogue<br />

diseased plants to prevent or slow its<br />

spread could provide a good basis for<br />

establish<strong>in</strong>g participatory experiments<br />

to help farmers multiply clean plant<strong>in</strong>g<br />

material of <strong>the</strong>ir preferred varieties.<br />

Action learn<strong>in</strong>g activities, <strong>in</strong>volv<strong>in</strong>g<br />

farmers <strong>and</strong> extension agents, could<br />

help improve <strong>the</strong>ir access to <strong>in</strong>formation<br />

<strong>and</strong> <strong>the</strong>ir underst<strong>and</strong><strong>in</strong>g of <strong>the</strong> causes<br />

<strong>and</strong> nature of <strong>the</strong> disease problem. This<br />

will provide opportunities to promote<br />

cultural control options such as<br />

appropriate methods of select<strong>in</strong>g<br />

plant<strong>in</strong>g material, sanitation <strong>and</strong><br />

rogu<strong>in</strong>g. Additionally, tra<strong>in</strong><strong>in</strong>g of<br />

national program partners would<br />

streng<strong>the</strong>n national capacity to<br />

<strong>in</strong>vestigate <strong>and</strong> promote <strong>the</strong> susta<strong>in</strong>able<br />

management of whiteflies <strong>and</strong> CMD.<br />

Acknowledgements<br />

The assistance of Dr. M. A. Bob of <strong>the</strong><br />

International Center of Insect Physiology<br />

<strong>and</strong> Ecology <strong>in</strong> <strong>the</strong> identification of<br />

<strong>whitefly</strong> species <strong>and</strong> natural enemies is<br />

recognized.<br />

References<br />

Burban, C.; Fishpool, L. D. C.; Fauquet,<br />

C.; Fargette, D.; Thouvenel, J. -C.<br />

1992. Host associated biotypes<br />

with<strong>in</strong> West African populations of<br />

<strong>the</strong> <strong>whitefly</strong> Bemisia tabaci (Genn.)<br />

(Hom., Aleyrodidae). J. Appl.<br />

Entomol. 113:416-423.

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