Next Gen Ag LLC historically has great success with natural soybean aphid populations in the area.  Our untreated checks have ranged from 1,200/plant to 250/plant averages over the years which, even on the low end, is 2.5X economical threshold.  Next Gen Ag has done variety, plant date, seed treatment, and foliar soybean aphid studies.  Typically we count a 5 plant sample per plot at each data collection period.