oa African Entomology - Infestation patterns and parasitism of the maize stalk borer, Busseala fusea (Fuller) (Lepidoptera: Noctuidae), in the Ivory Coast
The abundance and parasitism rates of preimaginal instars of the maize stalk borel; Busseola fusca (Fuller), were studied for the first time in the Ivory Coast. Maize crops were sampled in different ecological regions over a seven-year period. High population levels were only observed in the Mesophil sector of the Guinean ecological zone, where densities varied from 2-5 borers per stem in June plantings. Fluctuations in population density were attributed to three major factors: (1) timing of infestations, that appeared to be dependent on diapauses termination, which was influenced by rainfall at the end of March and during April; (2) numbers of larvae surviving diapause, that was dependent on severity of the dry season, on the occurrence of bush fires and on egg parasitism; (3) maize planting dates, which resulted in a coincidence between the plant growth stage favourable to the pest and the oviposition periods. Two egg parasitoids, Telenomus busseolae Gahan and T. isis Polaszek (Hymenoptera: Scelionidae) were collected. The first species was predominant (72 % of parasitized eggs). Five parasitoids were reared from larvae and pupae. Of these, Tetrastichus atriclavus Waterston (Hymenoptera: Eulophidae) was dominant (91 % of parasitized insects). The percentage parasitism of larvae and pupae was less than 10 % and appeared to have little influence on the population dynamics of B. fusca in the Ivory Coast.
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