Thurn, Anne Christine2024-01-042024-01-042010https://hdl.handle.net/10365/33555Plants can directly and indirectly influence the natural enemies of their herbivores. Such trophic level effects apply to plants in natural and agronomic settings as well as to plants bred for pest resistance and biological control of herbivores. The effects of host plant resistance on herbivore natural enemies are highly variable, depending on the system. Currently, there is great interest in breeding soybean for resistance to the soybean aphid (Aphis glycines Matsumura). However, little is known about the effects of soybean aphid resistance traits on soybean aphid natural enemies. This study looks at the indirect effects of plant resistance to soybean aphid on the lady beetle Harmonia axyridis Pallas (Coleoptera: Coccinellidae ), an important natural enemy of the soybean aphid, using seven soybean varieties that exhibited variable resistance 1o the soybean aphid. Aphids were collected from greenhouse-reared soybean plants and fed to beetles in the laboratory. Harmonia. axyridis larval development time, adult mass, and fecundity over a month were measured. Results indicated moderate and inconsistent indirect effects with highly resistant plant varieties while some moderately-resistant plant varieties reduced adult weight and egg production. My conclusion is that soybean aphid resistance is potentially compatible with H. axyridis biological control, but care must be taken when selecting varieties if there is more than one source of resistance or if plant resistance differentially affects soybean aphids and their natural enemies.NDSU policy 190.6.2https://www.ndsu.edu/fileadmin/policy/190.pdfSoybean -- Diseases and pests.Mite-eating ladybirds.Aphids -- Biological control.Thesis