Activity of extracts and compounds from New Zealand gymnosperms against larvae of Lucilia cuprina (Diptera: Calliphoridae)

A modified serum‐based bioassay was used to screen plant extracts and assess compound activity against newly hatched larvae of the Australian sheep blowfly Lucilia cuprina . Larval instar mortality and physical appearance were recorded after exposure for 24 h to the treatments. Extracts from New Zealand gymnosperms shown to have activity against L. cuprina larvae were: Podocarpus totara; P. acuteafolius; Dacrycarpus dacrydioides; Halocarpus bidwillii; H. biformis; H. kirkii; Lagarostrobos colensoi; Lepidothamnus intermedius; L. laxifolius; Phyllocladus tricho‐manoides; P. glaucus , and Agathis australis . The phytoecdysones 20‐hydroxyecdysone, 5,20‐dihydroxyecdysone, and ponasterone A inhibited larval moulting. Dyshomoerythrine, dacrysterone, and nagilactone C were insecticidal, with the latter also retarding growth at sublethal rates.