Research Article: Meta-analysis of yield response of foliar fungicide-treated hybrid corn in the United States and Ontario, Canada

Date Published: June 5, 2019

Publisher: Public Library of Science

Author(s): Kiersten A. Wise, Damon Smith, Anna Freije, Daren S. Mueller, Yuba Kandel, Tom Allen, Carl A. Bradley, Emmanuel Byamukama, Martin Chilvers, Travis Faske, Andrew Friskop, Clayton Hollier, Tamra A. Jackson-Ziems, Heather Kelly, Bob Kemerait, Paul Price, Alison Robertson, Albert Tenuta, David A. Lightfoot.


Foliar fungicide applications to corn (Zea mays L.) occur at one or more application timings ranging from early vegetative growth stages to mid-reproductive stages. Previous studies indicated that fungicide applications are profitable under high disease pressure when applied during the tasseling to silking growth stages. Few comprehensive studies in corn have examined the impact of fungicide applications at an early vegetative growth stage (V6) compared to late application timings (VT) for yield response and return on fungicide investment (ROI) across multiple locations.

Compare yield response of fungicide application timing across multiple fungicide classes and calculate the probability of positive ROI.

Data were collected specifically for this analysis using a uniform protocol conducted in 13 states in the United States and one province in Canada from 2014–2015. Data were subjected to a primary mixed-model analysis of variance. Subsequent univariate meta-analyses, with and without moderator variables, were performed using standard meta-analytic procedures. Follow-up power and prediction analyses were performed to aid interpretation and development of management recommendations.

Fungicide application resulted in a range of yield responses from -2,683.0 to 3,230.9 kg/ha relative to the non-treated control, with 68.2% of these responses being positive. Evidence suggests that all three moderator variables tested (application timing, fungicide class, and disease base level), had some effect (α = 0.05) on the absolute difference in yield between fungicide treated and non-treated plots (D¯). Application timing influenced D¯, with V6 + VT and the VT application timings resulting in greater yield responses than the V6 application timing alone. Fungicide formulations that combined demethylation inhibitor and quinone outside inhibitor fungicides significantly increased yield response.

Foliar fungicide applications can increase corn grain yield. To ensure the likelihood of a positive ROI, farmers should focus on applications at VT and use fungicides that include a mix of demethylation inhibitor and quinone outside inhibitor active ingredients.

Partial Text

Foliar fungicide applications to hybrid corn (Zea mays L.) have increased since the mid-2000s, due to reports that fungicides provide physiological benefits to crop plants that enhance yield even in the absence of disease [1–4]. Foliar fungicide applications in corn have been promoted at one or more timings ranging from early vegetative to late reproductive growth stages. The primary purpose of early vegetative stage (three-leaf collar to eight leaf collar growth stages; V3-V8; [5]) applications is to gain yield advantages from physiological benefits [6], while fungicide applications at the tasseling-silking corn growth stage (VT-R1) target both foliar disease management and yield gain from physiological response to fungicide [7]. Previous studies have indicated applications occurring at VT-R1 are most likely to be profitable when conditions favor disease development, such as planting hybrids susceptible to foliar diseases like gray leaf spot (caused by Cercospora zeae-maydis), northern corn leaf blight (caused by Exserohilum turcicum) and southern rust (caused by Puccinia polysora), planting into fields with high levels of corn residue, irrigated fields, and/or fields under continuous corn production [3, 7].

Yield response to fungicide application across all trials ranged from -2,683.0 to 3,230.9 kg/ha relative to the non-treated control (Fig 1). Of the 436 treatment-studies, 68.2% had a positive yield response, meaning regardless of application timing, fungicide active ingredient, or disease-base, greater yields occurred in fungicide treated plots than non-treated control plots. The overall yield response to fungicide application was 332.9 ± 29.1 kg/ha (95% CI = 275.8–389.8 kg/ha) and was significantly different from zero (P < 0.001). The decision of whether or not to apply a foliar fungicide to hybrid corn has become an annual occurrence in the US and Canada [21]. Farmers and certified crop advisors are most interested in increasing yield and profit in corn production [22], and with tightening profit margins, there is increased farmer interest in establishing the potential for profitability when using fungicides. Our results are consistent with other corn fungicide studies [6, 7], indicating that fungicide application often results in a positive yield response compared with not treating. However, questions remain regarding if yield increases are likely to be profitable, and how application timing influences return on investment. Our analysis demonstrates that certain fungicide classes (QoI, and DMI + QoI) can increase yield and profitability if applied at the VT (tasseling) corn growth stage. The effect size (D¯) for V6 (six leaf collar growth stage) applications was positive (127.4 kg/ha) and significantly different from zero, indicating modest yield gains, but the yield response at V6 was less than that for VT (376.8 kg/ha) and V6 + VT applications (493.9 kg/ha). These findings are consistent with previous research indicating that applications occurring at V6 are not likely to result in significant yield increases compared to VT applications [9–15]. In this study, mean yield response observed from VT applications was 2.9 times greater than V6 applications, resulting in a higher probability of return on investment from a fungicide application.   Source:


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