Roselle (Hibisicus sabdariffa L.) is a multipurpose malvaceous vegetable crop whose leaves, calyces, seeds, and seed oil are regularly used as food, food condiment and colorant; as phytomedicine for treatment of diverse ailments; or as raw materials in pharmaceutical, cosmetic and paint industries (Alarcon-Aguilar et al., 2007; Alarcon-Alonso et al., 2012; Ansari et al., 2013; El-Sheri and Sarwal, 2007, Halimatul et al., 2007; Olaniran et al., 2013). Its cut flowers and decorative red stalks and fruits are thriving export commodities (Alegbejo et al., 2003; Grubben et al., 2004). A variety of it, H. sabdariffa altissima, is an important fibre crop serving as substitute to jute in paper industry (McClintock and Tahir, 2004). Roselle is widely adapted to a variety of tropical and sub-tropical climatic conditions (El Naim et al., 2012). Sudan is the major producer and exporter.
In Nigeria, the cultivation of roselle straddles the diverse agro-ecological zones and it is largely peasantry, polycultural and purposively for food and income generation. In spite of the crop’s economic prospect, research on the biotic and environmental constraints to its production is limited. Roselle serves different purposes (shelter, oviposition or feeding site) for different insect species on it; species richness and diversity and the pest status of the insects infesting the crop vary from one location to another. Documentations of insects associated with the crop in Nigeria are decades old (Daramola, 1984; Dike, 1992) and they emanated from a limited production area.
For the purpose of pest management, detection of a new insect species, determination of the rate of species extinction and anthropogenic alteration of natural habitat, it is important to know the insect species, their relative abundance, diversity and richness on cultivated roselle in a particular agroecelogy (Humphries et al., 1995; Mirab-balou et al., 2017; Sisk et al., 1994). The findings in this regard of a pioneering study carried out at Makurdi, Benue State, in the Nigerian southern Guinea savanna are reported in this paper.
MATERIALS AND METHODS
A 48-plot field experiment laid in randomized complete block design with split-splitplot arrangement of treatments at the Agronomy Research Farm of Federal University of Agriculture, Makurdi (Latitude 07o 45′ – 07o 50′ N, Longitude 08o 45′ -08o 50′ E) was used for enumeration and collection of insects on green-calyx (H. sabdariffa var. altissima) and red-calyx (H. sabdariffa var. sabdariffa) roselle planted early and late in 2016 cropping season. Each plot was 5 m long and 5 m wide; adjacent plots and replications were separated 1 m and 2 m furrow, respectively. Plant stands were made comparable by thinning and replacing missing stands. Weeds were controlled manually and 100 Kg of NPK (15-15-15) fertilizer was applied.
Visual enumerations of insects were made between 0700 and 1000 h on plants enclosed by 1 m x 1 m quadrat in rows 2 and 4 of each plot from 3 weeks after planting (WAP) to harvest; the parts of the plant infested was noted before the insects were collected. The insects were killed in acetate jar and taken to the laboratory for sorting. At 50 % flowering and 50 % podding, five flowers and five pods were picked at random in rows 2 and 4 of each plot and opened to document number and species of insects found. Immature stages collected were reared to adult on appropriate food resource. Adult insects were identified at the Insect Museum of Ahmadu Bello University, Zaria.