Predation and Parasitisation of Prostephanus Truncatus by Teretrius Nigrescens and Anisopteromalus Calandrae Respectively under Controlled Environmental Conditions

Abstract

Laboratory studies   were conducted at Kpeve Agricultural Station in the Volta Region of Ghana and Crop Science Department, University of Ghana, to evaluate and compare the potentials of a predator, Teretrius nigrescens Lewis (formerly Teretriosoma nigrescens) (Coleoptera: Histeridae) and a parasitoid, Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae) as biological control agents against the larger grain borer, Prostephanus truncatus (Hom) (Coleoptera: Bostrichidae). The study was carried out using shelled maize grains infested with P. truncatus. In the experimental set up, the predation and parasitic abilities of T. nigrescens and A. calandrae respectively were evaluated in a controlled temperature and humidity chamber. The relative humidities were produced using saturated salt solutions of sodium chloride at 25°C, 30°C, and 35°C. The number of P. truncatus larvae consumed in 24 hours by T. nigrescens was found to be 5.02 ± 0.1 LGB larvae at 30°C, 75% r.h. Daily consumption rate of LGB larvae by T. nigrescens at other conditions of temperature and relative humidities were lower. Parasitic effect of A. calandrae was also high at 30°C, 70% r.h. (3.76± 0.20 larvae). At 25°C, significantly lower rates of parasitism were observed at70% r.h., 75% r.h. and 80% r.h. These findings suggest that in a situation where there is inadequate number of T. nigrescens for the control of LGB, A. calandrae could be used to augment the number of T. nigrescens for the control of the pest.

Keywords: Prostephanus truncatus, Anisopteropmalus calandrae, Teretrius nigrescens, predation, parasitism.