title: Antagonistic Interactions between the African Weaver Ant Oecophylla longinoda and the Parasitoid Anagyrus pseudococci Potentially Limits Suppression of the Invasive Mealybug Rastrococcus iceryoides.
abstract: The ant Oecophylla longinoda Latreille forms a trophobiotic relationship with the invasive mealybug Rastrococus iceryoides Green and promotes the latter's infestations to unacceptable levels in the presence of their natural enemies. In this regard, the antagonistic interactions between the ant and the parasitoid Anagyrus pseudococci Girault were assessed under laboratory conditions. The percentage of parasitism of R. iceryoides by A. pseudococci was significantly higher on "ant-excluded" treatments (86.6% ± 1.27%) compared to "ant-tended" treatments (51.4% ± 4.13%). The low female-biased sex-ratio observed in the "ant-tended" treatment can be attributed to ants' interference during the oviposition phase, which disrupted parasitoids' ability to fertilize eggs. The mean foraging time, host handling time and number of successful oviposition in "ant-excluded" treatment were significantly higher compared to "ant-tended" treatments. When ant workers were allowed access to sterilized sand grains, mummified and unmummified R. iceryoides, they selectively removed the mummified mealybugs, indicating that they recognized the mummies as potential foods (1.2 ± 0.46 to 7.8 ± 1.17 mummies at 10 min intervals for 2 h). Percentage emergence from mummified R. iceryoides removed by the ants was significantly lower compared to emergence from mummies not exposed to ants. Although, host seeking parasitoids frequently evaded attacks, some were killed by the foraging ant workers (2.0 ± 0.38 to 6.0 ± 0.88 at 10 min intervals for 2 h). These results suggest for the first time that the presence of O. longinoda has a detrimental effect on the abundance, reproductive success and possibly oviposition strategy of female parasitoids, which might be a delimiting factor in field conditions if both natural enemies are to be recommended for use within the same agro-ecosystem.
authors.affiliation: International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772, Nairobi 00100, Kenya. ctanga@icipe.org.|Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. ctanga@icipe.org.
authors.forename: Chrysantus M
authors.initials: CM
authors.lastname: Tanga
authors.affiliation: International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772, Nairobi 00100, Kenya. sekesi@icipe.org.
authors.forename: Sunday
authors.initials: S
authors.lastname: Ekesi
authors.affiliation: Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. prem.govender@smu.ac.za.|Faculty of Health Sciences, Sefako Makgatho Health Sciences University (SMU), P.O. Box 163, Ga-Rankuwa 0221, South Africa. prem.govender@smu.ac.za.
authors.forename: Prem
authors.initials: P
authors.lastname: Govender
authors.affiliation: International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772, Nairobi 00100, Kenya. pnderitu@icipe.org.
authors.forename: Peterson W
authors.initials: PW
authors.lastname: Nderitu
authors.affiliation: International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772, Nairobi 00100, Kenya. sfaris@icipe.org.
authors.forename: Samira A
authors.initials: SA
authors.lastname: Mohamed
keywords: Anagyrus pseudococci; Oecophylla longinoda; Rastrococcus iceryoides; biotic interference; mummy mutilation; parasitoid mortality