SOME ASPECTS OF GERMAN COCKROACH POPULATION ECOLOGY IN URBAN APARTMENTS

JOHN MICHAEL OWENS, Purdue University

Abstract

A broad base of population ecology research is prerequisite to the development of successful pest management programs for urban cockroach problems. The objective of this research was to make a significant, initial contribution to this process while answering certain specific questions on German cockroach (Blattela germanica (L.), BG) population ecology. Specific objectives led to studies of population sampling techniques, rates of BG movement within and between urban apartments, and effects of sanitation on BG populations infesting urban apartments. Eight BG sampling techniques (ST) were studied, both in laboratory mock-kitchen chambers and in urban apartments, to determine which were most effective and efficient for use in insecticide efficacy or population ecology research. Biases with regard to sampling nymph/adult and adult sex ratios were quantified. Mark-recapture (MR) procedures were utilized to measure adult BG movement rates within and between urban apartments. Three regions were identified within each of 2 adjacent, neighboring apartments located at either end of 4-apartment structures. Movement rates between these areas were studied over a 9-day period, which included 2 marking and 3 capture periods. Eight pairs of apartments were studied. In 4 pairs, the end apartment was treated with a pyrethrin aerosol and the effect of this treatment on BG movement rates was measured. Sanitation, when applied to BG-infested apartments, can affect the availability of 3 key factors which regulate population numbers--food, water and harborage. Professional janitorial services were hired to conduct thorough, general cleaning in 3 BG-infested urban apartments. Cleaning was conducted 2 times per week for 4 weeks. Adult BG populations were monitored during the week prior to janitorial work, the 4 weeks of janitorial work, and 1-2 weeks following. ST studies demonstrated that any of 3-4 BG traps and visual counting (flashlight assisted) can be used effectively in insecticide efficacy research and that their performance did not vary significantly with population density. Convenience and economic factors dictate that Mr. Sticky Traps (10-15/apartment) or visual counting be preferred for efficacy testing. In population ecology studies, the Reierson trap is preferred where MR procedures are not used. It is essentially unbiased for sampling across BG age classes, only slightly biased for sampling females among adults, and removes the smallest percentage of the total populatin of any trapping technique. Where MR procedures are required; baby food jar traps are the only non-destructive traps currently available. This ST is unbiased in sampling adult sexes and significantly biased for sampling adults compared to nymphs. Adult BG movement within and between urban apartments occurs at greater rates than literature sources have indicated. Intra-apartment movement rates were greatest between the kitchen and adjacent areas (20% over 5-7 days) and only slight (1-5%) between the upstairs and downstairs of 2-story apartments. Interapartment movement can be significant (10-30% over 5-7 days), but certain construction features appear to facilitate this movement. Pyrethrin aerosol applications increased adult BG movement out of treated apartments in 3 or 4 cases, and decreases intraapartment movement. Overall, adult male BG were more mobile than females. Sanitation procedures applied in this study had little effect on BG population numbers. Populations appeared to react to the sanitation program by altering their spatial distributions in the apartments, but population size did not decrease significantly. To be effective, pest management programs must be developed which integrate other factors besides sanitation procedures.

Degree

Ph.D.

Subject Area

Entomology

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