Diversity and abundance of diurnal insects associated with dry season Amaranthus hybridus L. in the University of Ilorin, Nigeria

Abstract

Amaranthus hybridus L. is an important leafy vegetable in sub Saharan Africa whose production is mainly limited by field insect pests. Integrated Pest Management (IPM) offers a sustainable approach for the management of these pests because it ensures effective insect pest control while also promoting the conservation of beneficial insect species in agro-ecosystems. Consequently, this study investigated the diversity and abundance of diurnal insects of dry season A. hybridus at the University of Ilorin to provide information for successful IPM programs in A. hybridus systems. Insect sampling from irrigated A. hybridus beds was done for 8 consecutive weeks from the second week after sowing. At each week, sampling was done in the morning (7:00 – 10:00A.M.), early afternoon (12:00 – 3:00P.M.) and late afternoon (4:00 – 7:00P.M.) with sweep net, aspirator and by handpicking. Seventy-eight insect specimens consisting of 24 species, 16 families, and 5 orders were collected. Herbivores in the family Acrididae, Alydidae, Chrysomelidae, and Pyrgomorphidae made up 78.3% of morning collections. Insect predators like Oecophylla sp. and Dorylus sp. in the family Formicidaewere most abundant in the early afternoon. Parasitoids in family Sphecidae and leaf feeders like Acridabicolor (Acrididae) made up 53.48% and 32.56% respectively of the total late afternoon collections. According to Shannon’s and Simpson’s diversity t- tests, insect taxa in the late afternoon were significantly (P < 0.05) less diverse than in the morning or early afternoon. In contrast, species richness in the morning and early afternoon did not differ significantly at P = 0.05.

Keywords: Amaranthus hybridus, IPM, predators, parasitoids, biodiversity