n African Entomology - Oviposition preference and survival of the maize stem borer, (Lepidoptera : Noctuidae), on Napier grasses, spp., and maize




Napier grass, , is used successfully as a trap crop for lepidopterous stem borers in Africa. This paper reports on the evaluation of the suitability of Napier grass varieties as trap crops for (Lepidoptera: Noctuidae). This was done through oviposition preference tests and evaluation of larval survival on different varieties. Napier grass varieties were collected from the wild, from research institutions and farmers growing them as forage crops. In multiple-choice tests with the different Napier grass varieties, differences in oviposition preference were observed. Results from two-choice tests with Napier grass and maize plants indicated moths have no marked difference in oviposition preference. However, compared to maize, larval survival on Napier grasses was low and a rapid decline in larval numbers was observed over the first week after inoculation on the grasses. A scanning electron microscope study of trichomes on Napier grass and maize leaves was conducted and the relationship between trichome number and larval survival determined. Significant negative correlations (P 0.03) were observed between trichome numbers and larval survival.


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