The soybean aphid, Aphis glycines Matsumara (Sternorrhyncha: Aphididae), is an exotic insect first discovered in Minnesota in 2000 and has been reported in 17 states and provinces. Nothing is known about how this aphid colonizes fields, and whether patterns might suggest early season management similar to other field crop aphids. In 2001, two small commercial fields were sampled using a ten plant sample unit. Colonization of soybean aphid appeared to be random and infestation became uniform by the early vegetative stage (V3). From data in 2001, we estimated the relative net precision for sampling, and a two plant sample unit was determined as efficient as a 5 or 10 plant sample unit. In 2002, our objective was to compare colonization in two different size fields. We selected four fields (two 4 ha and two 20 ha) to characterize colonization. All fields were grid sampled using six sample points per 0.4 ha counting the total number of aphids on each of two plants per sample point. Each field was sampled twice per week during the vegetative stage and then once per week until maturity. To determine if alatae landing rates were uniform, eight green-tile pan traps were placed in each field, changed once per week and aphids were identified to species. Soybean aphid populations were averaged, tested for spatial autocorrelation and the Geographic Information System ArcGIS was used to construct interpolated maps estimating the spatial and temporal distribution and density of soybean aphid for each collection date in each field.
Species 1: Homoptera Aphididae Aphis glycines (soybean aphid)
Keywords: population sampling, GIS
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