Pea aphid (Acyrthosiphon pisum) population growth in alfalfa in south central Wisconsin is regularly suppressed a suite of natural enemies, including a parasitoid wasp (Aphidius ervi) and several generalist predators (e.g., coccinellids, nabids). Disentangling the effects of these multiple natural enemies has been difficult, because manipulative experiments are necessarily limited in scale, and dynamic lags confound the interpretation of monitoring data. Moreover, conventional time series analyses of monitoring data do not provide ecologically meaningful results, and model-based analyses are plagued by non-identifiabilities between combinations of vital rates. Here, we present a state-space method for analyzing monitoring data that extracts the ecologically-meaningful information contained in the data, while shedding light on which aspects of aphid dynamics are not informed by the data. We use our method to analyze monitoring data from several alfalfa fields over the course of a growing season, and to ask if parasitism is responsible for the observed regulation of aphid populations.
Species 1: Homoptera Aphididae Acyrthosiphon pisum (Pea aphid)
Species 2: Hymenoptera Aphidiidae Aphidius ervi
Keywords: Biological control, Time series analysis
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