Production and processing of specialty crops in Wisconsin are very important to both state and national agricultural industries. And key among these processing crops in Wisconsin include sweet corn, succulent snap beans, field peas and potatoes. In addition, the vast majority of these commercial, contract acres receive an at-plant in-furrow, or seed treatment of a Group 4A insecticide (neonicotinoid). Increasingly, producers rely heavily on this single class of insecticides for control of early season pests including Colorado potato beetle, seed maggots, potato leafhopper, and bean leaf beetles (NASS 2006). Reported at-plant applications of these neonicotinoid seed treatments have occurred on nearly 90% of all acres reported and reflect statewide use rates in many other grain crops. In the 2014 and 2015 growing season, the in-plant concentrations of thiamethoxam (Cruiser® 5FS) were monitored using an ultra-performance liquid chromatographic mass spectrometry procedure in both leaf and floral tissues at varying stages after emergence from the soil.