Aspects of dispersal and population structure of Blattella germanica (L.) in field habitats and attitudes concerning aesthetic injury levels

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Virginia Polytechnic Institute and State University

Movement behavior of Blattella germanica (L.) was investigated using two mark-recapture techniques 1) marking field collected populations of adult German cockroaches with a unique number, and 2) releasing strains of genetically marked German cockroaches to observe nymphal movement.

Movement by adult cockroaches was studied by marking 3299 field collected German cockroaches in eight apartments. allowed for population. Adults were marked with Liquid Paper'. This recognition of specific individuals in the After marking, cockroaches were released at their original site of capture. Biological data was recorded on both nymphs and adults. Results indicate that movement of adult German cockroaches between apartments is minimal. Movement within apartments is greater, but not substantial. Movement appears to be linked to carrying capacity of the habitat (=apartment). When a vital resource -- food, water, or harborage -- becomes limited, adult movement can be detected when populations are large. Trapped populations in focus and non-focus apartments are spatially distributed in different ways. German cockroaches in non-focus apartments are trapped predominately in traditional sites of infestation kitchen and bathroom areas, with 90% of the collections occurring in these sites. In focus apartments trap collections indicate that one-third of the population is found in areas traditionally identified as non-preferred sites of infestation.

Movement of German cockroach nymphs was investigated using releases of genetically marked strains of cockroaches. Collections of marked individuals were limited, suggesting that the strains used, especially eye color mutants, were not competitive in field environments. Results of this study were inconclusive.

The feasibility of applying the aesthetic injury level concept to control programs within the urban environment rather than to pests occurring on the exterior was investigated. A random survey was conducted in non-elderly public housing projects in Roanoke, VA, Norfolk, VA, and Baltimore, MD. One hundred surveys were taken in each of the cities. The results of the survey indicate that the aesthetic injury level concept can not be successfully applied to control programs for insect pests occurring inside the home. are dependent upon the Tolerances extent of are variable, and the infestation experienced by each resident. It is speculated that as infestation levels decline, tolerance of the pest would also decline.