Herbivory assessments of Indian rose beetle (Adoretus versutus) on selected cultivars of bele (Abelmoschus manihot) in Samoa

Abstract

Bele (Abelmoschus manihot L.) is an indigenous and important leafy vegetable in the south Pacific region. However, herbivory by insects is a major problem in growing A. manihot. We investigated leaf damage by the Indian rose beetle (Adoretus versutus) in three selected cultivars NDASH LSQUOGreenRSQUO, LSQUORed BroadRSQUO and LSQUORed NarrowRSQUO of A. manihot at The University of South Pacific, Samoa. Plants of three ages (two months, four months and eight months old) were selected for this study. The level of herbivory by the beetle was measured by counting and measuring the number and size of holes in the top and bottom three leaves. The mean leaf area and shot-hole damage was higher in green compared to red cultivars. The number of shot holes per leaf was significantly higher in bottom leaves 23.4±2.2 compared to top leaves 4.5±2.7, suggesting that younger leaves were less preferred by the Indian rose beetle than older leaves. A positive relationship exists between herbivory and the age of plants. Since older plants are more attractive to the beetles, it is recommended to harvest the leaves before plants reach 8-months.