Abstract

Performance of oleander aphid (Aphis nerii Boyer de Fonscolmbe) and large milkweed bug (Oncopeltus fasciatus Dallas) on 21 species of Asclepias was evaluated in a two-year field study. Season-long pest and beneficial insect population growth was monitored. Plant quality ratings also were obtained. Relative numbers of Monarch butterfly (Danaus plexippus (Linnaeus)) larvae were also recorded. All milkweed species supported growth and development of oleander aphid except A. vestita, which failed to establish in this study. The only species that did not become infested with milkweed bugs were A. syriaca and A. sullivantii. The plant species with the lowest number of aphids, the highest plant quality ratings and the highest number of Monarch larvae (which is desirable as a larval food plant for the butterflies) was gooseplant, A. physocarpa. A.tuberosa cultivars also ranked high among all species tested.

Five insecticides were tested for efficacy against the Oleander aphid. All insecticide products evaluated: Endeavor (pymetrozine), Orthene (acephate), Merit (imidacloprid), Tempo (cyfluthrin) and Mpede (insecticidal soap) resulted in short-term reductions in aphids in field plots during 1999. Reinfestation occurred within two to three weeks. Parasitoids and predators were also suppressed to varying degrees by materials applied.