Journal of Insect Science (2008) 8 (4), 25-26

Samuel Kyamanywa, Peter Asiimwe, Michael Otim, Dan Gerling and James P. Legg (2008)
Within plant distribution of Bemisia tabaci and its principal parasitoids on cassava mosaic disease (CMD) resistant and susceptible varieties
Journal of Insect Science 8 (4), 25-26
in P. A. Stansly and C.L. McKenzie, organizers: Fourth International Bemisia Workshop - International Whitefly Genomics Workshop, December 3-8, 2006, Duck Key, Florida, USA
Abstract: Cassava mosaic disease CMD), caused by cassava mosaic geminiviruses and vectored by the whitefly, Bemisia tabaci, has been successfully managed using resistant cassava varieties. The CMD-resistant varieties, however, are heavily infested by B. tabaci causing direct injury resulting in significant reduction in tuberous root yield. Consequently there is a need to develop a CMD control strategy that also addresses the whitefly problem. Exploiting natural enemies is one of the strategies that is being explored. Knowledge of the distribution and incidence of the existing natural enemy fauna is a prerequisite for developing effective biological control. A study was therefore carried out to establish the distribution of B. tabaci parasitoids on cassava plants in order to determine the stage of the plant at which parasitoids start colonizing B .tabaci and to develop a sampling protocol for the parasitoids. The study was conducted using the CMD-resistant cassava variety, Nase 4 and the CMD-susceptible Ebwanateraka. There were significant differences in the distribution of both the whitefly and the parasitoids between different parts of the plant. For both varieties, over 65% of the whitefly nymphs were found on leaves 10 to 17 from the shoot apex of the plant. The density of B. tabaci nymphs decreased with age of the plant with over 60% of the nymphs occurring within 17 weeks after planting of cassava. Parasitism was highest on lower leaves (16 - 24). The level of parasitism varied with the maturity of the plant. Parasitism was least in young plants (11 weeks), highest in 19 week-old plants and thereafter dropped in plants more than 21 weeks old. Peak parasitism at a given growth stage depended on leaf position. For the susceptible variety, peak parasitism for young (11-13 week-old) cassava plants occurred on leaf number 14, while for older plants (17-19 week-old), parasitism peaked on leaves 18 and 21 respectively. The implications of the present findings for designing sampling procedures for both the whitefly and its parasitoids, and for studying the impact of the parasitoids on whitefly populations are discussed in this paper.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Samuel Kyamanywa, Michael Otim, James P. Legg

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
surveys/sampling/distribution
Research topic(s) for beneficials or antagonists:
surveys/distribution/isolation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Bemisia tabaci	Cassava (Manihot esculenta)