On the parasitization of the ladybird Coccinella septempunctata L (Col, Coccinellidae)

The present study deals with entomoparasites of Coccinella septempunctata L. in cereals, mainly in winter wheat. Sections of monthly sampled adult ladybirds during one year in different habitates at Staaken (Berlin) gave two peaks of parasitization with Perilitus coccinellae (Schrank) (Hym., Braconidae): (1) 33% in March (hibernation site); and (2) 12.5% in June (winter wheat). Populations of the ladybird investigated during the seasons in 1993 and 1994 in winter wheat at three locations (Berlin-Staaken, Flaming, Magdeburger Borde) showed a similar sharp increase in degree of parasitization with Perilitus coccinellae in the second half of June. Maximum of parasitization reached from 12.3% (Flaming, 1993) to 25% (Borde, 1993) and was a result of the act of the first newly emerged adult wasps. Main parasite of the coccinellid pupae was Phalacrotophora fasciata (Fallen) (Dip., Phoridae) with parasitization rates between 4.9% (Borde) and 20.2% (Flaming). Oomyzus scaposus (Thompson) (Hym., Eulophidae, Tetrastichinae) was found only at two locations with low rates: 0.9% (Flaming) and 1.4% (Berlin). Experiments in climatic chambers with alternating temperatures gave new results for the effect of Perilitus on the fertility of matured female ladybirds. At relatively high temperatures (25 degrees C middle of day) daily numbers of coccinellid eggs increased for a period of a week immediately after parasitization. Though mortality was high (70.6%) at this condition, half of the surviving females began egg deposition 12 days after emergence of the Perilitus larva.