Fungicide use in corn production in the United States was a rare practice for much of its history as a commercial grain. Only recently has fungicide increased rapidly, specifically between 2000 and 2010. While the use of fungicide on the crop grew exponentially, plant pathologists did not record an increase in fungal foliar disease pressure in corn.
A recently published study in the American Phytopathological Society’s (APS) Pathology Journal, “Perceptions of Midwestern Crop Advisors and Growers on Foliar Fungicide Adoption and Use in Maize” (Sept. 18), explains the various ideologies behind the exponential increase of foliar fungicide on corn crops during that 10-year period. The study uses survey responses from certified crop advisors (CCAs) and corn growers across Iowa Wisconsin, Ohio and Illinois.
According to the study, by the year 2007, nearly 10 percent of the country’s corn was being treated with fungicide. In 2010, a report by the Agricultural Resource Management Survey (ARMS), conducted by the U.S. Department of Agriculture (USDA), found that 22.5 percent of planted corn in Illinois had been sprayed with a fungicide.
For background information on the economical and agricultural technology landscape of the time periods being investigated, the report states that fungicides were commercially available to corn farmers since the 1980s. The Farm Crisis was occurring at this point in American history, and low commodity prices and low farm income continued until around 2000. In 2008, corn prices topped out at approximately $6 per bushel. Foliar fungicide use remained a rare practice through 1998, at which point it was mainly used in the production of high value hybrid corn seed. According to the report, “at that time, extension and crop advisors predicted no appreciable change in fungicide use over the next five years, because crop rotation and hybrid resistance would continue providing economically acceptable levels of disease control.”
However, this prediction did not come true. At the turn of the millennium, the mass adoption of shorter crop rotations and reduced tillage increased residue-born disease presence. Gray leaf spot (incited by Cercospora zeae-maydis) in corn was propelled — as predicted by researchers, according to the study — from the “sideline to international status.” An uncertainty in being capable of predicting foliar disease outbreaks was also on the rise, as corn prices began to trend upward. Around this time also came the registration of quinone outside inhibitor (QoI) fungicides for corn. The mass marketing of these products to farmers was integral at this time, due to the mechanism of which QoI’s worked. These types of fungicides were able to last longer in direct sunlight, and had activity against a broad spectrum of fungi. Perhaps more intriguing than the aforementioned benefits were claims that this class of fungicides could boast plant health benefits, such as green leaf longevity and improved stalk strength.
The study sought to understand CCAs and corn growers’ perceptions on fungicide use during this time period, as well as measure the average perceived benefit and/or consequences of this increase in fungicide use. Increased fungicide use with no increase in disease pressure went against researchers’ observed behavior of corn farmers, whose decision making has been very much dependent on profitability. These behaviors also go against the practices of integrated pest management (IPM), which urges responsible pesticide use through information-based decision making and multiple other management tools for pest control. The report states that multiple university trials across the U.S. Corn Belt had shown inconsistent profitability under low foliar disease severity.
The survey was sent to 188 CCAs and 188 corn growers in each states, totaling 1,504 individuals, with a response rate of 47.4 percent. From 2005 through 2009, 73 percent of all CCAs recommended the use of a foliar fungicide on corn. Just 35 percent of corn growers applied a foliar fungicide. Of this total, 84 percent were applying a fungicide for the first time, while 68 percent of CCAs who recommended spraying had done so for the first time. When it came to ranking threats to corn production however, weeds were the number one concern (90 percent by CCAs and corn growers), followed by insects and then diseases. The perception on behalf of corn growers when it came to disease impacts on yield loss varied among the states evaluated, however the study did not examine the disease pressures and other circumstances in each state.
When asked to rank corn production factors from most to least important, approximately 23 percent of respondents ranked the use of foliar fungicide as being “very-extremely important." The top four factors were maximizing profit, yield, commodity prices and plant population, followed by “other factors” (which includes trait resistance and Roundup Ready seed). Those who held disease as more important to impacting yield loss were more likely to perceive foliar fungicides as more important.
The breakdown of CCA recommendation of foliar fungicide use varied by the use of the end product: 98 percent recommended applications to grain, 35.7 percent to seed crops and 24.3 to silage. Of corn growers who applied fungicide, 94 percent applied fungicide to grain, 24.8 percent applied to seed crops and 27.7 percent applied to silage.
Yield Benefits or Loss
The impacts on crop yield, conditional on having sprayed a foliar fungicide were as follows: 94.4 percent of CCAs and 65.1 percent of corn growers saw a 5 to 9 bushel per acre increase (a 4.08 percent increase per year average); 47.4 percent of CCAs and 25.6 percent of corn growers saw a negative yield response of 1 to 4 bushels per acre.
The study also examined how much CCAs and corn growers were willing to spend on foliar fungicide, as a way to examine the economic decision making during this period. Approximately 20 percent of CCAs believed that their corn growers were willing to spend $25 or more per acre, while corn growers reported a willingness to spend only between $16 and $38 per acre. The use of fungicide in previous crop production years had an influence on the amount that corn growers and CCAs were willing to spend. For those who had sprayed fungicides in the last 5 years, the odds of being willing to spend $25 or more per acre on fungicides compared with less were 5.2 times the odds for those who did not spray fungicides being willing to spend $25 or more per acre compared with less.
Land Steward vs. Businessperson
Upon reviewing the data collected in the study, researchers concluded that corn growers struggle with “balancing the conflicting roles of environmental stewardship and successful businessperson. In reality, short-term profit-making trumps the environmental stewardship role.” Researchers further concluded that the use of fungicide in the absence of disease pressure, while disagreeing with IPM protocols, was seen as a form of insurance to protect yields with commodity prices spiking in the period examined. Since fungicides at this time covered a broad spectrum of fungi while also boosting plant health, the cost might have been worth the investment. The survey indicated that, on average, farmers observed yield responses above the break-even point. Though CCAs are influencers, and were more likely to recommend fungicide if they perceived disease to be important, corn growers were more skeptical, and viewed disease resistance as a seed trait/treatment to be more beneficial. Given the current state of commodity prices, it can be inferred that prices per bushel will influence growers’ attitudes toward using a fungicide.