A milkweed mystery: An aphid and its natural enemies

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 various Asclepias species and honeyvine milkweed, Cynanchum laeve. Experimentation during 2008 - 2010 demonstrated that A. nerii fitness is influenced by differing physical and chemical characteristics among four of its host plant species in Kentucky. In addition to altering aphid fitness, host plant quality may also influence the fitness of predators and parasitoids utilizing A. nerii as a resource. It was hypothesized that a correlation existed between A. nerii fitness and the fitness of its natural enemies. During 2009 and 2010, laboratory experiments were conducted to compare predator development, adult predator fecundity, and parasitoid efficacy when utilizing A. nerii reared on different host plant species. Field experiments monitored the attraction of predators to natural infestations of A. nerii on different host plant species. Additionally, the richness and abundance of parasitoids utilizing A. nerii as well as the occurrence of parasitism and subsequent successful emergence of parasitoid adults within natural A. nerii infestations were investigated. Field experiments included both first year and older milkweed host plants.