Diversity, relative abundance and temporal spread of insects associated with Roselle (Hibiscus sabdariffa L.) at Makurdi, Nigeria

Abstract

Roselle, Hibiscus sabdariffa L., is cultivated extensively for food and income generation in Africa, but research on biotic constraints to its production has been scanty. A 48-plot (5m×5m wide each) field experiment laid in randomized complete block design was used to document the relative abundance (% RA), diversity, richness, and temporal spread of insect species infesting the crop at Makurdi, Nigeria. The insects were collected from all parts of early- and late-sown green-calyx (H. sabdariffa var. sabdariffa) and red-calyx (H. sabdariffa var. altissima) Roselle shoots. About 101 species (81 herbivores, 18 predators, 1 parasitoid, and 1 pollinator) in 45 families and 8 orders were collected. Shannon’s diversity index (2.1-2.4) and Margalef’s richness index (8.3-10.0) indicate a rich diversity of species on the crop. However, evenness of species, measured by Buzas and Gibson’s index, was low (0.1-0.41). The orders Coleoptera and Hemiptera accounted for 72.0% of the collection. Nineteen species were moderately (≥1 RA<5%) to highly abundant (RA≥10%) on the crop and among them Monolepta thompsoni Allard and Nisotra sjostedti Jac. were ubiquitous causing extensive leaf perforation all through the entire crop growth period. At the reproductive stage of growth, Dysdercus volkeri Fab., Oxycarenus hyalinipennis Costa and Earias sp. were the dominant insects causing fruit and seed damage. The frequency of occurrence and densities of M. thompsoni Allard, N. sjostedti Jac., D. volkeri Fab., O. hyalinipennis Costa and Earias sp. as well as their extensive damage, indicate that they are the key field pests of Roselle at Makurdi.