D3290: Milkweed aphid host selection and potential consequences for monarch conservation

Oleander aphids (Aphis nerii) are a nonnative insect commonly found in gardens, mainly on milkweed plants (Asclepias spp.). They reproduce quickly and live at such a high density that they can negatively impact the host plant. Because milkweed hosts a broad community of native invertebrates, Aphis nerii also impacts other invertebrates when they occur on the same plant. Part of this milkweed community are monarchs (Danaus plexippus), whose larvae rely solely on milkweed plants. Monarchs are experiencing a population decline that has caused alarm for monarch enthusiasts and conservationists, and research is currently aiming to mitigate abiotic and biotic factors to increase success of summer generations. Previous research has found indirect impacts from A. nerii on monarch larvae, such as increased growth and disease transmission. An area of focus for current research is which species of milkweed plant results in the most successful monarch larvae, but A. nerii host species preference and success, which could change their interactions with monarchs, has not yet been explored. Using lab-reared adult aphids, we tested initial plant choice and population establishment on the three milkweed species most commonly planted for conservation efforts in Pennsylvania (Asclepias syriaca, A. tuberosa, and A. incarnata). Our findings suggest that A. nerii do have preferences for certain host plant species, but that their individual success rate does not differ between milkweed species. These results can be applied to monarch management strategies to decrease negative impacts from A. nerii presence.