Studies On The Suitability Of Parkia Biglobosa (Jacq.) [African Locust Bean] For The Development Of Sitophilus Zeamais Motschulsky (Coleoptera: Curculionidae).

ABSTRACT

Maize is an important staple food crop in Ghana and is cultivated throughout the country. The Guinea savanna zone in the Northern region, which is fast becoming a major production zone, is also the natural ecological zone o f Parkia plants. Some insect pests, such as Sitophilus zeamais are a serious threat to maize production in Ghana. These insects appear to have adapted to and survive on some wild host plants. They may therefore emigrate from these alternative hosts to preferred hosts when the crops are planted in the field. The objective o f this study was to investigate the suitability of Parkia biglobosa for the development o f S. zeamais and also to determine whether S. zeamais adults would exhibit any preference for Parkia substrates when given a choice. A comparative study o f the development o f S. zeamais on Parkia seeds, pulps, pods and maize showed that the weevil does not reproduce at all on Parkia substrates under both field and laboratory conditions. Mean developmental period on maize under controlled conditions was significantly (P < 0.05) shorter (41.2 days) than under ambient environmental conditions (47.0 days). The mean weight of adults (3.4mg) under controlled conditions was, however, not significantly different (P > 0.05) from what was obtained under ambient environmental conditions (2.8mg). The mean number o f eggs laid on maize under controlled conditions was significantly (P < 0.05) higher (114.5) than under ambient environmental conditions (94.75) and no eggs were laid on Parkia seeds, pulp and pods. In free-choice tests, significantly (P < 0.05) more weevils were recorded on maize than on Parkia substrates under both sets o f conditions. Comparative study on survival of S. zeamais on Parkia seeds, pulp, pods and maize variety Volta local showed that survival o f the weevils stabilized with time on maize but high mortality was recorded on Parkia seeds, pulp and pods under both sets o f conditions. More weevils survived on Parkia seeds, pulp and pods in an environmental chamber in the laboratory than under the field conditions. From this, no conclusion can be drawn that Parkia pods, pulp and seeds may act as alternate hosts for S. zeamais and investigation needed to be undertaken to determine the actual factors responsible for the unsuitability or unacceptability of Parkia biglobosa as a host for S. zeamais. It is suggested that a better understanding o f the biology and behaviour o f S. zeamais in relation to Parkia pods, pulp and seeds will assist in the development o f improved management practices for the control of this pest and so reduce heavy losses caused by this pest both in the field and storage.