The primary impact of herbicide resistance for most Iowa farmers has been an increase in expenditures for herbicides. I decided to do a quick analysis of this by using ISU Extension’s annual Estimated Costs of Crop Production (A1-20). Estimated herbicide costs/acre from 2000-2017 are shown in Figure 1.
Other than the bump in herbicide costs in 2009, the graphs are what I expected. The decline in herbicide cost for soybean during the early 2000’s is likely due to a decrease in glyphosate price as alternative glyphosate products entered the market.
The spread of glyphosate resistant weeds around 2013 forced a large percentage of growers to abandon the glyphosate only programs that dominated the soybean market since the introduction of Roundup Ready varieties.
The resistance problem isn’t going anywhere, and without adopting alternative weed management strategies we can only expect the increases in herbicide costs to continue.
Costs are based on surveys of prior year’s usage and adjusted for inflation or other expected price changes.
Thus, there would be a year lag in cost increases due to changes in herbicide programs due to a rise in herbicide resistance within fields.