Effects of local landscape composition on Colorado potato beetle (Leptinotarsa decemlineata) colonization of commercial potato in Wisconsin

In Wisconsin, founding populations of Colorado potato beetle typically infest potato along field edges resulting in season-long pest pressure. Differences in abundance of beetles both within and between fields are thought to be influenced by the proximity and abundance of previous potato. Though important, previous potato does not consistently explain variability in annual infestation patterns in the potato agroecosystem. This raises the question: Is there a landscape composition surrounding potato that relates to the abundance of Colorado potato beetle in commercial fields? In this study we related landscape composition with beetle abundance to identify locations of high and low colonization risk. Specifically, points sampled for Colorado potato beetle abundance in 2008 were hierarchically clustered into thirteen groups based on habitat composition within 1,000m radius. When beetle abundance data were aggregated by cluster three distinct levels of beetle pressure were apparent. Averaged landscape attributes for each cluster generated from 2008 data were used to select 30 points of high and low risk at random from 301 potato fields, in 2012, based on the habitat composition adjacent to the field edge. Selected points were counted over four weeks and the response of Colorado potato beetle was expressed as accumulated insect pressure over time. Colonization of high and low risk clusters showed no significant differences in the first two weeks of the study (t=-0.3522, df=56, p-value=0.73). Preliminary results in 2012 indicate that more data are needed to further inform our understanding of the habitat composition adjacent to potato fields that influences beetle abundance.