Systematic & Applied Acarology ISSN 1362-1971 An international journal of the Systematic and Applied Acarology Society, published since 1996 [Aims] [Editors] [Content] [Subscriptions] [Contact details] [Society Homepage]

Systematic & Applied Acarology (2002) 7, 77-90

Relationships between leaf trichome characteristics and field resistance to cassava green mite, Mononychellus tanajoa (Bondar)

E. N. NUKENINE 1, 4, A. G. O. DIXON 2 , A. T. HASSAN 3 & F.G. ZALOM 4

1 Department of Biological Sciences, Faculty of Science, University of Ngaoundere, PO Box 454, Ngaoundere,

Cameroon; E-mail: en_nukenine@yahoo.co.uk (Author for correspondence)

2 International Institute of Tropical Agriculture, PMB 5320, Ibadan, Nigeria; E-mail: A.dixon@cgiar.org

3 Department of Zoology, University of Ibadan, Ibadan, Nigeria

4 Department of Entomology, University of California, Davis, California 95616, USA; E-mail: fgza-lom@

ucdavis.edu, ennukenine@ucdavis.edu)

Abstract

Experiments were conducted at Ibadan, Nigeria to assess the effect of leaf trichome characteristics (pubescence

intensity index, length, and orientation) on field resistance of cassava to the green spider mite, Mononychellus

tanajoa (Bondar). There were significant (P < 0.01) differences in M. tanajoa density, damage score and leaf

trichome characteristics among the cultivars. During the dry season (February, 1993 and 1994) and the early

part of the rainy season (May, 1993), there were significant (P < 0.01) negative correlations between pubescence

intensity index on the top leaves (leaf 3) and mite damage. Significant negative correlations were also obtained

between trichome length and damage in the dry season (February, 1993) (P < 0.05), and between trichome

orientation and mite damage in the rainy season (May, 1993) (P < 0.01). Correlation between pubescence

intensity index and mite density on the top leaves was significant and positive only in the "middle" of the rainy

season (August, 1993). A significant (P < 0.01) negative correlation was obtained between trichome orientation

and mite density in the dry season (February, 1993). The results suggest that, during the dry season, a high

pubescence intensity significantly reduces leaf damage by M. tanajoa through mechanical disturbance of

movement and feeding. Trichome length is more important than trichome orientation in cassava resistance to

M. tanajoa.

Key words: cassava, leaf trichome, host plant resistance, Mononychellus tanajoa

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