Entomologia Experimentalis et Applicata (2000) 95, 283-291

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Catherine Bertschy, Ted C.J. Turlings, Anthony Bellotti and Silvia Dorn (2000)
Host stage preference and sex allocation in Aenasius vexans, an encyrtid parasitoid of the cassava mealybug
Entomologia Experimentalis et Applicata 95 (3), 283-291
Abstract: The solitary endoparasitoid Aenasius vexans Kerrich (Hymenoptera: Encyrtidae) is used for augmentative releases against the cassava mealybug, Phenacoccus herreni Cox and Williams (Sternorrhyncha: Pseudococcidae), an important pest on cassava in South America. In light of the need for large numbers of high quality females, experiments were conducted on host stage suitability and sex allocation. In choice and no-choice experiments, individual female wasps were offered second and third instar, as well as adult, hosts. During the first five days after emergence, the wasps showed a steady increase in the number of hosts they successfully parasitised per day, but the respective secondary sex ratio for each instar remained constant. Parasitism was highest for third instar hosts in no-choice tests, while in choice tests parasitism was highest in both third instars and adults. The later the developmental stage of the host at oviposition, the faster the parasitoids developed and emerged, and for each host stage, the development time of males was shorter than for females. The sex ratio of the wasps emerging from hosts that were parasitised as second instars was strongly male-biased, while the apparently preferred later stages yielded significantly more females than males. Female and male A. vexans emerging from hosts parasitised at the third instar were significantly larger than for the other stages. This may explain the preference for the third instar as well as the female-biased sex ratio, as size is usually positively correlated with higher fitness, especially in females. The results suggest that third instar hosts are the most suitable for rearing high numbers of large females.
(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): Ted C.J. Turlings

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
general biology - morphology - evolution

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Phenacoccus herreni Cassava (Manihot esculenta) Colombia
Aenasius vexans (parasitoid) Phenacoccus herreni Cassava (Manihot esculenta) Colombia