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Extension > Minnesota Crop News > Fungicide for corn? The influence of agronomic factors in 2008

Fungicide for corn? The influence of agronomic factors in 2008

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Jeff Coulter,
Extension Corn Agronomist
In the past few years, the use of foliar fungicide on corn has gained considerable attention. In 2008, with generous support from the Minnesota Corn Growers Association and BASF, research was conducted in southern Minnesota at Lamberton and Waseca to determine how planting date impacted corn response to foliar fungicide. In these trials, corn followed soybean at 32,400 plants per acre, and the hybrid was DKC52-59. At both locations, there was little to no foliar disease at the time of fungicide application. The same was true at the early dent stage, regardless of whether fungicide was used. Nonetheless, yield was generally 3 to 4% (5 to 6 bushels per acre) higher when fungicide was applied, regardless of planting date or location (Figures 1 and 2). The exception was the early planting date at Waseca, where foliar fungicide resulted in a 6% yield increase (Figure 1). However, these numerical yield increases were not statistically significant, even at the 10% probability level. In other words, additional replication is needed in order to ensure that these differences are actually due to the treatments imposed, rather than random variability in soil productivity from one plot to the next.

Figure 1. Impact of fungicide on corn yield for three planting dates at Waseca, MN in 2008. Results are from DKC52-59 in a corn-soybean rotation. Differences between treatments were not statistically significant at the 10% probability level for any planting date.
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Figure 2. Impact of fungicide on corn yield for three planting dates at Lamberton, MN in 2008. Results are from DKC52-59 in a corn-soybean rotation. Differences between treatments were not statistically significant at the 10% probability level for any planting date.
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It is unclear why yields were numerically higher in the planting date trials when fungicide was applied in the absence of foliar disease (Figures 1 and 2). It may be that fungicide keeps the leaves green for a few more days in the fall, thereby extending the duration of grain fill. This hypothesis is supported by the harvest moisture data from these trials (Figures 3 and 4), which show that the grain tended to be a little wetter when fungicide was applied. However, differences in harvest moisture between treatments were not statistically significant in any planting date at either location. Thus, caution should be used when interpreting these results.

Figure 3. Impact of fungicide on corn grain moisture at harvest for three planting dates at Waseca, MN in 2008. Results are from DKC52-59 in a corn-soybean rotation. Differences between treatments were not statistically significant at the 10% probability level for any planting date.
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Figure 4. Impact of fungicide on corn grain moisture at harvest for three planting dates at Lamberton, MN in 2008. Results are from DKC52-59 in a corn-soybean rotation. Differences between treatments were not statistically significant at the 10% probability level for any planting date.
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In another study from 2008, corn response to foliar fungicide was evaluated in corn following corn in southwest (Lamberton) and central (Brownton) Minnesota. In both trials, a conventional tillage system was used and corn residue covered 35 to 37% of the soil surface after planting. In these trials, final stands were 30,500 plants per acre, and the hybrids were DKC53-18 at Lamberton and Garst 87G94 at Brownton. Even though these trials followed corn and residue from the previous crop was abundant on the soil surface, there was little to no foliar disease at the time of the fungicide application. In addition, there was little to no foliar disease at the early dent stage, even in plots that did not receive fungicide.

In these corn following corn trials, yields were low, especially at Lamberton where it was exceptionally dry (Figure 5). In addition, yield differences between treatments were not statistically significant at either location. These trials were also harvested relatively early (>22% grain moisture), and grain moisture was 1.2 to 1.8 points wetter at harvest where fungicide was applied (Figure 6). However, these differences in harvest moisture were not statistically significant.

Figure 5. Impact of fungicide on yield in corn following corn at Lamberton and Brownton, MN in 2008. Hybrids were DKC53-18 at Lamberton and Garst 87G94 at Brownton. Differences between treatments were not statistically significant at the 10% probability level at either location.
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Figure 6. Impact of fungicide on grain moisture at harvest in corn following corn at Lamberton and Brownton, MN in 2008. Hybrids were DKC53-18 at Lamberton and Garst 87G94 at Brownton. Differences between treatments were not statistically significant at the 10% probability level at either location.
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Growers considering foliar fungicide for corn in the absence of disease should realize that this is not a "best management practice" from an integrated pest management standpoint. They should also consider the cost of the application, statistical significance of research results, the consistency of grain yield and harvest moisture response to fungicide treatments from one trial to the next, and their ability to tolerate economic risk. In 2009, we will continue to evaluate corn response to foliar fungicide for various planting dates in southern Minnesota. Additional information on corn production from the University of Minnesota is available on our new corn website: www.extension.umn.edu/corn.

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