Submitted to: Annals of the Entomological Society of America
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/1/2001
Publication Date: 1/1/2002
Citation: NANSEN, C., MEIKLE, W.G., KORIE, S. SPATIAL ANALYSIS OF PROSTEPHANUS TRUNCATUS (HORN) (BOSTRICHIDAE: COLEOPTERA) FLIGHT ACTIVITY NEAR MAIZE STORES AND IN DIFFERENT FOREST TYPES IN SOUTHERN BENIN, WEST AFRICA. ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA. 2002. Interpretive Summary: 1. Problem: Prostephanus truncatus, an important, introduced pest of stored maize and cassava in Africa, are often caught with pheromone traps in forests. If the forest is carefully mapped with respect to tree species and ecozones, what can intensive trapping at 16 sites over 76 weeks reveal about where the beetles live in the forest, and where they start flying earliest? If the ecology of the beetle in the forest is known, we might be able to develop better control strategies. 2. Approach: Set up an intensive trapping network, change the traps each week, count the beetles in each trap each time they are changed, and conduct two types of statistics: looking for correlations between trap catches and tree species or ecozone, and evaluate how nonrandom the data is. If the data is very nonrandom, this means there is a valid pattern in it. 3. Results: The beetles were found to be flying earliest and in great numbers in a part of the forest dominated by teak, which is an imported, plantation tree and is not known to be a host of the beetle. This is an interesting result, since it may mean the beetles are feeding on seeds or roots, or parts of the trees where no-one has looked before. The spatial pattern was found to be highly nonrandom, and beetles were trapped in greatest numbers in the forest, and only after that were large numbers caught in agricultural areas.
Technical Abstract: Weekly Prostephanus truncatus (Horn) flight activity (measured as captures of beetles in pheromone baited traps) was monitored during 76 consecutive weeks at 16 sites inside the Lama forest in southern Benin and at four sites in maize farmland just outside the forest. Prostephanus truncatus flight activity was consistently higher and the flight activity pattern significantly different near maize stores compared to inside the forest. Although P. truncatus is known to infest girdled branches of Lannea nigritana (Sc. Elliot) Keay, the P. truncatus flight activity was very low at forest sites where this tree species dominated. The main peak in P. truncatus flight activity occurred earlier in the eastern part of the forest compared to other forest parts . Ordination analysis showed that comparatively higher flight activity in the eastern part of the forest was positively associated with the occurrence of teak plantations (Tectona grandis Linn. F.) at trap sites. The spatial distribution pattern of weekly P. truncatus flight activity was found to be significantly aggregated during a 21 week period, which coincided with the early build-up in P. truncatus flight activity in the eastern part of the forest. The present analysis indicated that P. truncatus individuals disperse from the eastern part of the forest to other forest parts and to nearby agricultural areas, rather than, as has been suggested, from maize stores to the forest environment.