Effect of Maize Hybrid and Foliar Fungicides on Yield Under Low Foliar Disease Severity Conditions

Abstract

Foliar fungicide use in the U.S. Corn Belt increased in the last decade; however, questions persist pertaining to its value and sustainability. Multistate field trials were established from 2010 to 2012 in Illinois, Iowa, Ohio, and Wisconsin to examine how hybrid and foliar fungicide influenced disease intensity and yield. The experimental design was in a split-split plot with main plots consisting of hybrids varying in resistance to gray leaf spot (caused by Cercospora zeae-maydis) and northern corn leaf blight (caused by Setosphaera turcica), subplots corresponding to four application timings of the fungicide pyraclostrobin, and sub-subplots represented by inoculations with either C. zeae-maydis, S. turcica, or both at two vegetative growth stages. Fungicide application (VT/R1) significantly reduced total disease severity relative to the control in five of eight site-years (P<0.05). Disease was reduced by approximately 30% at Wisconsin in 2011, 20% at Illinois in 2010, 29% at Iowa in 2010, and 32 and 30% at Ohio in 2010 and 2012, respectively. These disease severities ranged from 0.2 to 0.3% in Wisconsin in 2011 to 16.7 to 22.1% in Illinois in 2010. The untreated control had significantly lower yield (P<0.05) than the fungicide-treated in three site-years. Fungicide application increased the yield by approximately 6% at Ohio in 2010, 5% at Wisconsin in 2010 and 6% in 2011. Yield differences ranged from 8,403 to 8,890 kg/ha in Wisconsin 2011 to 11,362 to 11,919 kg/ha in Wisconsin 2010. Results suggest susceptibility to disease and prevailing environment are important drivers of observed differences. Yield increases as a result of the physiological benefits of plant health benefits under low disease were not consistent.

Effects of Pyraclostrobin Foliar Fungicide, Corn Hybrid, and Harvest Timing on Stalk Health of Corn

“…It is difficult to determine if this statistically significant reduction in stalk rot severity by a value of 0.5 on the 0 to 5 stalk rot severity rating scale would result in a difference in stalk lodging if strong winds were present; however, the risk of lodging would be greater as the stalk rot severity values increase. Although not always consistent, reductions in stalk rot with the use of foliar fungicides also have been observed by other researchers (Adee and Duncan, 2017;Hines, 2007;Mallowa et al, 2015). For Harvest Timing 1, the lowest stalk rot severity ratings occurred in the two hybrids with moderate resistance to gray leaf spot (HRN and HRB), which were lower than the stalk rot ratings of the two hybrids with susceptibility to gray leaf spot (HSN and HSB) ( Table 3).…”

Effect of the addition of a fungicide to glyphosate applied postemergence on crop injury, disease control, and corn yield

“…Dingley (synonym: Kabatiella zeae Narita & Hirats.)] and Physoderma brown spot (Physoderma maydis Miyabe), but a single rating was made for combined foliar diseases as reported by Mallowa et al (2015). Corn grain yield and moisture content were measured at harvest using a Wintersteiger small plot combine equipped with a Grain Gage weighing system.…”

Cercospora zeinafrom Maize in South Africa Exhibits High Genetic Diversity and Lack of Regional Population Differentiation

“…Management of GLS in commercial maize in USA and South Africa is conducted by foliar fungicide treatments (Mallowa et al 2015;Ward et al 1999), resulting in high selection pressure for fungicide resistance in the pathogens. Our study has indicated high levels of genetic diversity in C. zeina from South African maize growing regions, which suggests mechanisms for mutation or recombination within the population, with implications for the development of fungicide resistance.…”

“…strobilurins) are popular foliar fungicides due to perceived additional plant health benefits (Mallowa et al 2015), however development of resistance by Cercospora species has been documented. Isolates of C. sojina from soybean have exhibited reduced sensitivity to QoI fungicides in several USA states (Standish et al 2015;Zeng et al 2015;Zhang et al 2012), and QoI resistance in C. beticola from sugarbeet has been reported from USA and Italy Bolton et al 2013).…”

“…Chemical control is an important component of disease management. Maize foliar fungicide applications have increased in the USA over the past decade (Mallowa et al 2015), and anecdotal evidence suggests that applications have increased in other maize production areas around the globe, including South Africa. Widespread adoption of conservation tillage has allowed many fungal foliar pathogens to over-winter on maize debris, thus increasing the inoculum pressure in subsequent growing seasons (Ward et al 1999).…”