Distribution and sampling of Prostephanus truncatus (Coleoptera: Bostrichidae) and Sitophilus zeamais (Coleoptera: Curculionidae) in maize stores in Benin

The distribution among and within grain stores of 2 grain store pests, Prostephanus Truncatus (Horn) and Sitophilus zeamais Motschulsky were examined over time using different maize cultivars. Incidence in stores was variable between seasons for both species. The b coefficient of Taylor's power law did not differ among maize cultivars. Within-store distribution among cobs could be approximated by the negative binomial and an overall k parameter was estimated for both species. These data were used to develop sampling plans to estimate sample size needed to determine insect density for both pest species over different densities given a desired precision. Sequential sampling stop lines were calculated to determine pest status given action and no-action threshold densities. The possibility of applying the sampling plans as an integrated pest management tool is discussed

Establishment, spread, and impact of Teretriosoma nigrescens (Coleoptera: Histeridae), an exotic predator of the larger grain borer (Coleoptera: Bostrichidae) in southwestern Benin

Studies were carried out between 1992 and 1997 in southwestern Benin to investigate the establishment, spread, and impact of Teretriosoma nigrescens Lewis, a natural enemy of the larger grain borer, Prostephanus truncatus (Horn). Trap data, using the 2-component synthetic aggregation pheromone of P. truncatus , from 5 different surveys, carried out twice yearly over a 3-yr period, showed a rapid establishment and spread of the predator throughout the region. Increasing numbers of T. nigrescens in the pheromone traps were associated with decreasing numbers of P. truncatus . Pheromone trap data, collected weekly at a small number of sites over the entire study period, revealed a yearly bimodal peak in flight activity of P. truncatus in 1992, 1993, and 1994. The 1st peak in flight activity of P. truncatus was sharply reduced in 1995, 1996, and 1997, accompanied by increasing numbers of T. nigrescens in the pheromone traps. Data from on-farm storage experiments and from surveys in farm-stored maize, Zea mays L., showed a considerable reduction of P. truncatus infestation, and decreasing losses of maize, coinciding with the increasing presence of T. nigrescens