A comparative study on the leaf feeding activities of Raphidopalpa femoralis (Coleoptera; Chrysomelidae) on two cucurbits and their wild relatives

Abstract

New varieties of Cucumis melo and Momordica charantia are highly susceptible to the leaf feeding insect pest Raphidopalpa femoralis. Feeding of R. femoralis on leaves of the M. maderspatana and M. dioica which are wild relatives of C. melo and M. charantia, respectively have been rather poorly documented in Sri Lanka. Thus, present study investigated the comparative analysis of R. femoralis damage on selected crops and their respective wild relatives by leaf feeding bioassays, host preference studies using olfactometre, and leaf card index in the field. Feeding bioassay results of R. femoralis on leaves of crop plant C. melo and its wild type M. maderspatana indicated that the mean damage of the wild plant M. maderspatana was significantly higher than that of the crop plant C. melo (P<0.05). In contrast, mean damage of R. femoralis on leaves of crop plant M. charantia were significantly higher than the wild plant M. dioica leaves (P<0.05). Food choice tests using two crop plants and the respective two wild relatives indicated that the leaves of M. maderspatana had the highest mean damage (0.6483 ±0.057), while C. melo had the lowest damage (0.0056±0.0069). The leaf damage of M. charantia and M. dioica were recorded as 0.4078±0.0433 and 0.1533±0.0080 respectively. Leaf card Index studies conducted under the field conditions revealed that the damage of the crop plant leaves were significantly different (P<0.05) than the damage of its wild plant leaves. Olfactometre studies indicated that R. femoralis had significantly higher positive responses to the leaves and leaf extractions of wild plant M. maderspatana than that of crop plant C. melo (P<0.05). However, leaves and leaf extractions of crop plant M. charantia had significantly higher positive responses than the wild relative, M .dioica (P<0.05). Present research findings give much important preliminary information related to R femoralis damages in selected cucurbits and their wild relatives