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The oriental cockroach, Blatta orientalis L., was found to be an important seasonal household pest. Of 151 residents interviewed in two Roanoke apartment complexes in Virginia, 90% had seen oriental cockroaches, 60% considered one oriental cockroach indoors to be a problem, and 77% had taken steps to control these cockroaches. Monitoring oriental cockroach populations indicated when and where treatment would be necessary to reduce cockroach infestations. The adult cockroach population peaked in late June and July, and declined through August and September while the number of nymphs increased. Eighty percent of all cockroaches trapped at Roanoke apartment buildings were caught at porches, the primary cockroach harborage sites. In a mark-recapture study at four apartment buildings, 50% of the resighted oriental cockroaches remained at one porch, 36% moved along one side of a building, 13% moved between the front and back of a building, and 2% moved between two buildings. Only 1-5% of the oriental cockroaches marked outdoors were ever captured indoors.
One exterior perimeter and crawlspace application of encapsulated chlorpyrifos or diazinon in early June was the most effective insecticide treatment, reducing oriental cockroach populations by at least 85% for two months. Oriental cockroaches populations were reduced 78% and 50% two months after application of Dursban 4E (chlorpyrifos) and Combat bait trays (hydramethylnon), respectively. Structurally modifying buildings, to limit cockroach access to harborage in porch and wall voids, did not significantly (P < 0.05) reduce oriental cockroach populations, even one year after treatment. Structural modification was labor intensive, requiring at least eight times more man-hours per building compared to insecticide applications.
The evaniid wasp Prosevania punctata (Brullé) had been seen in apartments by 60% of the Roanoke residents interviewed. This wasp parasitizes and destroys the oothecae of oriental cockroaches. P. punctata exhibited a maximum parasitization rate of 51% for oothecae of oriental cockroaches in laboratory conditions. Three peaks of evaniid wasp field populations closely followed the rise, peak, and decline of adult oriental cockroach populations. A resident education program significantly (P < 0.05) reduced the percentage of residents in Roanoke apartment complexes who thought evaniid wasps were a problem or killed them. However, evaniid wasps parasitized only 15% of the field collected oriental cockroach oothecae, significantly fewer (P < 0.05) than the 36% parasitized by the eulophid wasp Tetrastich us hagenowii. In addition, 60% of the residents still killed evaniid wasps, despite the education program. |
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