The oleander aphid sandwich: tri-trophic interactions in milkweed systems

The oleander aphid, Aphis nerii Boyer de Fonscolombe, is a cosmopolitan herbivore that feeds on members of the milkweed (Asclepiadaceae) family. In central Kentucky, A. nerii colonizes several common Asclepias species and honeyvine milkweed, Cynanchum laeve. In 2008, experimentation demonstrated that A. nerii fitness differs among these plant species. Beginning in 2008 and continuing in 2009, host plant characteristics, including cardenolide concentrations, were examined on milkweed plants of varying age. Field experiments monitoring natural colonization by A. nerii, as well as predator and parasitoid richness and abundance were completed. Characteristics affecting A. nerii fitness were identified. In addition to altering aphid fitness, host quality might also influence predation on the aphid. It was hypothesized that a correlation existed between predator development and A. nerii fitness. In 2009, laboratory experiments were conducted to compare predator development and survival on A. nerii reared on different host plant species. A randomized complete block design was used for all experiments.