The influence of aphids (Myzus persicae) and pink lady beetle larvae (Coleomegilla maculata) on host plant preference of imported cabbageworm (Pieris rapae)

Authors: Lundgren, Jonathan; LAYMAN, MARISSA - South Dakota State University

Submitted to: Arthropod-Plant Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/3/2015
Publication Date: 9/1/2015
Citation: Lundgren, J.G., Layman, M.L. 2015. The influence of aphids (Myzus persicae) and pink lady beetle larvae (Coleomegilla maculata) on host plant preference of imported cabbageworm (Pieris rapae). Arthropod-Plant Interactions. 9:507-514.

Interpretive Summary: Butterflies have to weigh a number of factors when deciding when and where to lay an egg. This is particularly important from a pest management perspective for caterpillar pests. One factor that needs to be considered is when potential competitors (e.g., aphids) or predators (e.g., lady beetle larvae) are present on a potential host plant. We tested the influence of these other insects on oviposition choices made by the imported cabbageworm on canola. The presence of aphids did not affect oviposition choice by butterflies. Lady beetle larvae alone also didn’t affect oviposition preference. However, when the aphids and lady beetle larvae were both on the plants, significantly fewer eggs were laid. One possible explanation for this pattern is that butterflies can sense alarm pheromones given off by the aphids, and choose to avoid these plants.

Technical Abstract: Oviposition decisions by herbivorous insects hinge on multiple factors; host plant quality, enemy free space, plant density, offspring performance, and competition for resources all which influence decisions by an ovipositing female. Here, we evaluate whether the presence of aphids (a competitor) or a lady beetle larva (a predator) influence host plant selection by an ovipositing butterfly. In preliminary trials, the butterfly Pieris rapae (L.) (Lepidoptera: Pieridae) had similar larval survival on three putative Brassicaceae host plants, but Myzus persicae (Sulzer) (Hemiptera: Aphididae) had greatest population growth on canola (Brassica napus L.). Based on this information, canola was used as a host plant to determine the influence of aphids and predators on the oviposition behavior of the imported cabbageworm butterfly females by using a factorial design. Butterflies highly preferred plants that had no other insects present and this was reflected in the high number of eggs laid. The presence of a competitor herbivore (aphids) had no effect on butterfly oviposition behavior. However, predators significantly influenced the number of eggs and the location of where eggs were laid on the plants, especially on those plants that had both aphids and a lady beetle larva present in combination.