Hydroprene effects on the dynamics of laboratory populations of the German cockroach (Dictyoptera: Blattellidae).
The influence of sterilization by hydroprene on population dynamics in the German cockroach, Blattella germanica (L.), was studied in the laboratory where more detailed and accurate assessments could be achieved than would be possible under typical field situations. The gradual accumulation of sterile adultoids (i.e., adults with twisted wings, indicating exposure to hydroprene) during treatment, or their decreasing abundance after treatment, produced distinctive patterns in the dynamics of treated populations. The percentage of gravid females (a reproductive index) was first to respond to treatments, because increases (or decreases) in the percentage of gravid females preceded reductions (or recoveries) in sample density and nymph-to-adult ratios by 4-6 wk. Trends in the percentage of adultoids were negatively correlated with the percentage of gravid females and indirectly measure the activity of hydroprene. Initial reductions in the percentage of gravid females, sample density, and nymph-to-adult ratios began at or about the time when approximately 80% of adults had twisted wings (i.e., were adultoids). As the percentage of adultoids attained (or declined below) the 80% level, we can accurately predict the subsequent decline (or recovery) in nymph-to-adult ratios and, thus, sample density. These data support a proposal to adopt the 80% level of adultoids as an action threshold for regulating juvenoid treatments to maximize population suppression. The role of this action threshold in the long-term management of chronic B. germanica infestations or insecticide resistant populations is discussed.
Reid
B L
BL
Department of Entomology, Purdue University, West Lafayette, IN 47907.
Bennett
G W
GW
D000818:Animals; D003058:Cockroaches / Q000187:drug effects*; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology*; D005260:Female; D007814:Larva / Q000187:drug effects; D008297:Male; D008452:Maximum Allowable Concentration; D011157:Population Dynamics; D012098:Reproduction / Q000187:drug effects; D013997:Time Factors
D005231:Fatty Acids, Unsaturated; C006481:ethyl-3,7,11-trimethyl-2,4-dodecadienoate