The potential of alfalfa fields as early-season nurseries for natural enemies of Plathypena scabra (F.) (Lepidoptera: Noctuidae)

Field studies were conducted to determine the potential of alfalfa fields as early-season nurseries for biotic agents of green cloverworm (GCW), Plathypena scabra (F.), mortality in soybean. Low levels of Nomuraea rileyi (Farlow) Samson infection in alfalfa GCW populations were detected in June and early July. Inocula from N. rileyi-killed larvae in alfalfa fields may disperse to surrounding areas and contribute to the nearly simultaneous development of N. rileyi epizootics in alfalfa and soybean GCW populations during late July and August. Parasitoid activity and number of predatory arthropods were greater in GCW populations in alfalfa fields than in soybean fields, especially during the early season. Very likely, these biotic mortality agents emigrated from harvested alfalfa fields to nearby habitats, including soybean, where host populations were more abundant or the habitat was more suitable.