Untersuchungen zum saisonalen Auftreten von chalcidoiden Parasitoiden in einer Apfelbaumkrone 1999-2004

Seasonal occcurrence of chalcid parasitoids in an apple tree canopy 1999-2004. Tree canopy research is detecting a high biodiversity of arthropods even in urban areas. Continuous observation and monitoring provides basic information that is needed for enviromnent saving concepts and detailed research programmes. Parasitic hymenoptera are playing an important role as natural enemies and control agents of economical relevant pests. The reduction of pesticides for enhancing and saving beneficial arthropods is gaining growing interest. An overview on biodiversity of parasitic wasps in Germany shows that there is little known in some groups although they are the largest group of insects, together with the Coleoptera. The Chalcidoidea are of importance because of beneficial insects like the white fly parasitoid Encarsia formosa or Trichogramma species as natural enemies of lepidopterous pests. In Germany, about 1.800 chalcid wasps are know out of 18 families, in which the pteromalids are the largest group. Samples were taken from an apple tree canopy almost every day from 1999-2004. The tree had a canopy size from about 48 m3, leaf surface of about 80 m² and a height of 4,5 m. It is placed in an urban garden area and was never treated with pesticides within the last 45 years. From more than 38.000 caught specimens 2.400 parasitic wasps and as a part of those 800 Chalcidoidea could be identified. The percentage rate of Chalcidoidea from total wasps was 30-50 %. In 2003 to 2004 the sampling rate was smaller because of the growing age, loss of leaf mass and growing areas of non-living wood in the tree canopy. The results show a seasonal occurence of chalcidoidea wasps correlated with weather conditions and the avaibalility of host species.