Environmental Entomology (2003) 32, 51-60

Rose Ndemah, Fritz Schulthess, Samuel Korie, Christian Borgemeister, Hans-Michael Poehling and Kitty Cardwell (2003)
Factors affecting infestations of the stalk borer Busseola fusca (Lepitoptera: Noctuidae) on maize in the forest zone of Cameroon with special reference to scelionid egg parasitoids
Environmental Entomology 32 (1), 51-60
Abstract: The effect of vegetation, intercropping, and Telenomus spp. egg parasitism during the vegetative stage of maize on Busseola fusca (Fuller) (Lepitoptera: Noctuidae) infestations and maize yields at harvest were studied during two consecutive cropping seasons, in the humid forest zone of Cameroon. Six locations grouped into three blocks, representing gradients in human population densities of 15–88 inhabitants/km² were chosen. The fields were located at 20–90 min walking distance from the next road. Differences between blocks in the measured variables were mostly not significant indicating that the population density gradient was not strong enough to affect length of fallow period and thereby vegetation, the population dynamics of pests and natural enemies, and maize yields in forest fields. Numbers of egg batches per plant but also egg parasitism by and sex ratio of Telenomus spp. were significantly higher during the second than the first season (66.9 versus 19.9% and 0.67 versus 0.21, respectively). As a result, the number of borers per plant was only 0.22 versus 0.73 during the first season. Similarly, total mortality of immature B. fusca was 60.5% during the first and 93.2% during the second season. The seasonal differences in unexplained mortality was probably because rainfall caused drowning of migrating first instars. High mean parasitoid mortality at the beginning of the first season was probably caused by high superparasitism promoted by low host density conditions. Across seasons, abundance of grasses in the surroundings of a field was negatively related to egg batch density. Likewise, numbers of B. fusca decreased with increasing density of the nonhost cassava in the field, indicating increasing mortality of migrating larvae. Egg numbers per plant was negatively and egg parasitism or parasitoid sex ratio was positively related to yield.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Rose Ndemah, Fritz Schulthess, Christian Borgemeister, Hans-Michael Poehling, Kitty F. Cardwell

Research topic(s) for pests/diseases/weeds:
environment - cropping system/rotation
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
environment/habitat manipulation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Busseola fusca	Maize/corn (Zea mays)	Cameroon