Aspects of Insecticidal action of Piper guineense Schum and Thonn fruit powders against Callosobruchus maculatus F. (Coleoptera:Bruchidae)

Abstract

Under laboratory conditions (28 ± 3°C and 70 ± 5% r.h.) in Akure, Nigeria, powders of different particle sizes (212 um, 300 um, 500 um and 1 mm, respectively) made from ripe Piper guineense Schum and Thonn fruits, were evaluated at five rates of application (0, 0.1, 0.2, 0.3, 0.4 and 0.50 g/20 g of seed), for insecticidal action against Callosobruchus maculatus (F.), a major storage pest of cowpea, Vigna unguiculata (L.) Walp. Treatments involved introducing freshly emerged beetles onto protected and unprotected cowpea seeds in airtight glass tubes or plastic plates. Irrespective of particle size of powder, all rates of application significantly reduced (P < 0.05) oviposition and adult emergence of C. maculatus compared with the control. Similarly, all introduced freshly emerged adult beetles were killed within 36 hours. The susceptibility of adult beetles to P. guineense powder increased significantly with the age of the beetle. Powder of particle size of 212 um was always more potent than powder of particle size of 1mm.