The Response of Predatory Insects to Landscape Structure

Colunga-Garcia, M. and S.H. Gage

Presented at the All Scientist Meeting (1996-07-16 to 1996-07-17 )

Management of agroecosystems to enhance natural regulation of insect pests requires an understanding of predator ecology and how predatory insects use the landscape and respond to its structural characteristics. A group of predatory insects, ladybird beetles, were selected to study patterns of habitat utilization in response to vegetation type, management practices, and habitat succession in a complex agricultural landscape.The field work was conducted at the Long Term Ecological Research (LTER) site at the Kellogg Biological Station (KBS), in southwest Michigan. First, a life systems study of Coleomegilla maculata lengi was conducted by sampling wooded habitats to determine beetle aggregation sites in the landscape, and by using stable isotopes to determine paths of energy flow in the beetle-crop system. Secondly, abundance patterns of fourteen species of coccinellids were monitored weekly during the growing season using yellow-sticky traps. The sampled landscape consisted of an array of field crops under different management practices, interspersed with perennial biomass plantations and vegetation in a state of secondary succession. Seven years of weekly abundance records were analyzed using Shannon Wiener and richness indices, Kendall’s coefficient of concordance, and principal component analysis. The results of the analysis were used to produce a spatially explicit population model for comparative analysis of landscape-predator interactions.The main findings of the study were:Within the framework of the KBS LTER theme that ecological knowledge can replace chemical subsidies, this work contributes to the role that management practices can have on beneficial insects and identifies landscape characteristics conducive to maintaining higher numbers of beneficial insect predators within agroecosystems.

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