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