A 2-year study in a vegetable-growing area (Tori, Hla Avamé) in Benin has shown that the invasive aphid parasitoid Lysiphlebus testaceipes (Cresson) was attacked by three species of native hyperparasitoids. On several occasions, hyperparasitoids emerged from more than 90% of the mummies collected. The dominating hyperparasitoid was Syrphophagus africanus (Gahan). Two species in the genera Pachyneuron (Pteromalidae) and Aphanogmus (Ceraphronidae), respectively, were also recorded as hyperparasitoids. Charipinae hyperparasitoids were lacking. The only aphid host present at Hla Avamé was Aphis gossypii Glover, a dominating species in vegetable agroecosystems in Benin.

Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae, Aphidiinae) is a newly discovered species alien to Benin (West Africa) and the dominating aphid primary parasitoid in vegetable agroecosystems. A study on the preference of this parasitic hymenopteran for three key aphid pests of vegetables (Aphis craccivora Koch, Aphis gossypii Glover and Lipaphis erysimi (Kaltenbach) (Homoptera: Aphididae)) was carried out under choice and no-choice conditions at 26 ± 1 °C in both Petri dishes and cages. The aphidiine rejected L. erysimi and did not oviposit in this aphid species in any of the trials. In all tests, A. gossypii proved to be the aphid host preferred most frequently by L. testaceipes. This study contributes to the fundamental knowledge on the oviposition behaviour of L. testaceipes and provides information for use in the development of sustainable aphid pest management strategies in Benin.

The interactions between the cowpea aphid Aphis craccivora Koch, its parasitoid Lysiphlebus testaceipes Cresson and hyperparasitoid Syrphophagus africanus Gahan were assessed in the laboratory. Host age preference for hyperparasitism was evaluated using parasitized aphids of different ages (i.e. 1, 2, 3, 4, 5 and 6 days old and mixed ages). We studied the influence of the hyperparasitoid on the parasitism efficiency of L. testaceipes, the effect of host age on some biological parameters of S. africanus, and its hyperparasitism based on aggregated or isolated mummies. The presence of S. africanus significantly affected aphid parasitism by L. testaceipes (21.2 ± 3.6 vs 36.6 ± 4.5%). Except for 1-day-old hosts, S. africanus successfully parasitized hosts of all tested ages, with preference for newly formed mummies (39.16 ± 3.31% parasitism in 5-day-old hosts). The development time of immature stages of the S. africanus progeny was significantly affected by host age. The sex ratio of the hyperparasitoid progeny was largely female biased and did not vary with host age. Syrphophagus africanus females from live parasitized aphids produced more offspring (36.55 ± 6.28 vs 25.00 ± 7.16) and lived longer (21.09 ± 1.57 vs 10.88 ± 2.31 days) than those from mummy hosts. Hyperparasitism rates were higher on aggregated mummies than on dispersed ones (36.00 ± 2.86 vs 20.66 ± 4.00%).

Predation on parasitized hosts can significantly affect natural enemy communities, and such intraguild predation may indirectly affect control of herbivore populations. However, the methodological challenges for studying these often complex trophic interactions are formidable. Here, we evaluate a DNA-based approach to track parasitism and predation on parasitized hosts in model herbivore-parasitoid-predator systems. Using singleplex polymerase chain reaction (SP-PCR) to target mtDNA of the parasitoid only, and multiplex PCR (MP-PCR) to additionally target host DNA as an internal amplification control, we found that detection of DNA from the parasitoid, Lysiphlebus testaceipes, in its aphid host, Aphis fabae, was possible as early as 5 min. post parasitism. Up to 24 h post parasitism SP-PCR proved to be more sensitive than MP-PCR in amplifying parasitoid DNA. In the carabid beetles Demetrias atricapillus and Erigone sp. spiders, fed with aphids containing five-day-old parasitoids, parasitoid and aphid DNA were equally detectable in both predator groups. However, when hosts containing two-day-old parasitoids were fed to the predators, detection of parasitoid prey was possible only at 0 h (immediately after consumption) and up to 8 h post consumption in carabids and spiders, respectively. Over longer periods of time, post-feeding prey detection success was significantly higher in spiders than in carabid beetles. MP-PCR, in which parasitoid and aphid DNA were simultaneously amplified, proved to be less sensitive at amplifying prey DNA than SP-PCR. In conclusion, our study demonstrates that PCR-based parasitoid and prey detection offers an exciting approach to further our understanding of host-parasitoid-predator interactions.