oa Journal of the Entomological Society of Southern Africa - The effect of single and mixed populations of Busseola fusca (Lepidoptera: Noctuidae) and Chilo partellus (Lepidoptera: Pyralidae) on damage to grain sorghum
Field damage to grain sorghum by Chilo partellus (Swinhoe) and Busseola fusca (Fuller) in both separate and mixed populations, was compared using different levels of artificial infestation on caged plants. At high infestation levels, plant damage and yield loss caused by the two borer species was very similar. However, C. partellus was more injurious to tillers, as indicated by higher numbers of damaged internodes and reduced yield. Damage and yield loss increased when B. fusca and C. partellus formed mixed populations. Compensation for borer damage was reflected by increases in branch yield relative to total yield. Damage did not increase above a critical infestation level of 20 eggs and this was ascribed to a density dependent mechanism which prevents overcrowding of larvae in individual stems. Regression equations descriptionbing the relationships between infestation levels and both whorl damage and yield loss were determined for each pest species in both separate and mixed populations.
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