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n African Entomology - The role of parasitoids in suppressing diamondback moth, (L.) (Lepidoptera : Plutellidae), populations on unsprayed cabbage in the North West Province of South Africa

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Abstract

The role of parasitoids in suppressing diamondback moth, (L.) (Lepidoptera: Plutellidae), populations was studied for two years (February 2000 - January 2002) on unsprayed cabbage plots near Brits, North West Province, South Africa. Cabbage seedlings were transplanted three consecutive times each year. Infestations by , and the incidence of its parasitoids, were monitored at weekly intervals throughout the study period. The flight activity of male moths was also monitored at weekly intervals using synthetic sex-pheromone traps. Trap catches indicated that moths were active throughout the year and their flight activity corresponded with larval infestations on the crop. Trap catches and infestation levels were low in summer, autumn and winter (December-August) and high in spring (September-November). Eight indigenous parasitic Hymenoptera were reared from : the larval parasitoids (Kurdjumov) (Braconidae) and (Ullyett) (Braconidae), the larval-pupal parasitoids (Kurdjumov) (Eulophidae) and (Holmgren) (Ichneumonidae), the pupal parasitoid (Gravenhorst) (Ichneumonidae), and the hyperparasitoids sp. (Eurytomidae), sp. (Ichneumonidae), and sp. (Pteromalidae). Parasitism rates of larvae were high reaching 100 % on several occasions during late spring, summer and autumn (November-May) each year. Parasitism was lower (<50 %) in winter and early spring (June-September). was the most abundant parasitoid of followed by . Both parasitoids were active throughout the year. was absent only in winter. Only one specimen of was recorded, in spring, during this study. A high rate of parasitism of pupae by was observed only in spring (September-October). Hyperparasitism rates were high in spring and summer (September-February) when up to 35 % of collected larvae and cocoons yielded hyperparasitoids. The roles of biotic and abiotic mortality factors on the population dynamics of are discussed.

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/content/ento/13/1/EJC32624
2005-03-01
2016-12-07
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