[A model of cockroach control in a large area. II. Occurrence and distribution of Blattella germanica and Blatta orientalis in the district of Potsdam (GDR)--an infestation analysis].

Blattella germanica and Blatta orientalis occur in the district of Potsdam (German Democratic Republic). B. germanica is the real cause of plague. Up to now 2,734 building properties have been infested with cockroaches. B. germanica was found in 2,644 properties; B. orientalis was found in 20 properties and both were found in 70 properties. Infestation with cockroaches increases with urbanisation. Infestation is especially frequent in works canteens and similar rooms. Outdoor distribution of cockroaches takes place passively in food transports. Inside buildings cockroaches spread through cracks in walls, through pipings, lift shafts etc. 70 to 80% of the properties infested by cockroaches are works canteens, shops, restaurants, hotels and bakeries. B. germanica was found in 82% of the larger hospitals and outpatients' clinics, in about 72% of the works canteens, in about 26% of the restaurants and hotels, in about 20% of the bakeries and the enterprises manufacturing beverages, in 17% of the shops, in 8.8% of the nurseries and crèches and in a smaller percentage in flats and newlybuilt residential areas.