Impact of Automated Guidance for Mechanical Control of Herbicide Resistant Weeds in Corn

The use of herbicide weed control has been an integral part of farm management for several decades due to being an efficient and cost-effective alternative to mechanical weed control management. However, repeated use of broad spectrum herbicides has resulted in herbicide resistance in several weed species (Norsworthy et al., 2012). Although the indiscriminate use of herbicides has been linked to the quick and widespread adoption of herbicide resistant crop species (Fernandez-Cornejo et al., 2014), research indicates that herbicide resistance predated the introduction of bio-tech crops by several decades (WSSA, 2016). By the time that USDA began tracking the adoption of biotech soybean production in 2000, over half of US acreage were planted to herbicide-tolerant varieties and reached over 90% within 7 years (USDA NASS) (Figure 1). By 2013, 90% of corn and soybean acreage were planted to bio-tech cultivars including herbicide-tolerate only and stacked genes (Figure 1). Currently, 470 unique cases of herbicide resistance have been documented (Heap, 2016). Multiple herbicide-resistant weed species causes additional concern due to reduced herbicide options and increased weed control costs. Multiple herbicide resistance has been confirmed in economically important weeds including Palmer amaranth (Amaranthus palmeri) (Nandula et al. 2012), waterhemp (Amaranthus tuberculatus Sauer) (Bell et al., 2013), horseweed (Conyza canadensis L. Cronq.) (Davis et al. 2009), rigid ryegrass (Lolium rigidum Gaudim) (Owen et al. 2014), and kochia (Kochia scoparia (L.) Schrad.) (Foes et al. 1999) (see Heap, 2016, for more details on herbicide resistance weeds).