Entomologie, Ornithologie und Herpetologie: Aktuelle Forschung
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Interim Diets for Specialist Predators of Hemlock Woolly Adelgids

Allen Cohen C and Carole Cheah ASJ

We provide a rationale for diets that temporarily support populations of insects but not sustained rearing of target insects. We call such sustaining media, “interim diets”. We present formulation and performance details of such a diet, which sustains specialist adult predators of hemlock woolly adelgids (HWA) for several months. The diet base is ground, freeze-dried, cooked chicken breast, heat-treated chicken egg yolk with several nutritional and functional supplements. This diet has been tested in our laboratories for five years and has been validated in several mass-rearing laboratories where HWA predators are routinely produced. Although the current diet does not support complete development of HWA predators from egg to adult, it is useful as an economical and convenient means of keeping predators alive and healthy during periods when natural prey are not available. Unlike generalist predators, HWA predators would not accept factitious hosts such as scale, aphids, lepidopteran eggs or other foods that might have sustained them during “feeding droughts”. The predators studied here were beetles, Sasajiscymnus tsugae (Coccinellidae) and Laricobius nigrinus (Derodontidae). We experimented with several diet-presentation systems designed to fulfill the feeding requirements of the beetles and to preserve the diets by preventing desiccation and deterioration. We developed several forms of a hen’s egg-based diet and a diet-presentation system that included alginate gels and slurry diets that were made from adhering liquid materials to a solid/capture medium (freeze dried, powdered chicken breast). Some diets and diet-presentation systems induced strong feeding responses and allowed adult predators to stay alive and active for several months and to return to egg production days after being returned to HWA. The paper describes a stable, palatable diet and dietpresentation techniques that allow researchers and mass-rearing facilities to sustain healthy populations of predators during regular periods of prey scarcity.