Volume 6 Issue 6     June 30, 2009

Corn Response to Fungicide in Minnesota: Results from 2007 and 2008

In the past few years, the use of foliar fungicide on corn has gained considerable attention. In 2008, research was conducted in southern Minnesota at Lamberton and Waseca to determine how planting date impacted corn response to foliar fungicide. 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 the fungicide application (tasseling) or at the early dent stage, regardless of whether fungicide was applied. In these trials, corn grain yield with fungicide was not statistically different than that without fungicide for any planting date at either location, even at the 10% probability level (Figure 1 and Figure 2). In other words, yield differences from one plot to the next resulting from factors such as soil productivity were greater than yield differences due to the fungicide application. In these same trials, grain moisture at harvest was not significantly greater when fungicide was applied (data not shown).

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 chisel plow 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 lower, especially at Lamberton where it was exceptionally dry (Figure 3). 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 4). However, these differences in harvest moisture were not statistically significant.

In 2007, replicated on-farm trials evaluated the response of corn grain yield to fungicide applied at tasseling using field-scale equipment at 25 locations in southern and central Minnesota (Figure 5). In these trials, corn generally followed soybean, hybrids differed among locations, and the use of fungicide was economical at only 4 of the 25 sites. It is unclear why there was an economically positive response at four sites, but a neutral or negative response at the other 21 sites, as there was no relationship between responsiveness and factors such as yield potential, previous crop, or hybrid susceptibility to foliar diseases or stalk rot.

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. Positive responses of corn grain yield to foliar fungicide have been more consistent under warmer temperatures and higher humidity in the central and southern Corn Belt, particularly when corn follows corn, minimum tillage systems are used, leaf diseases such as gray leaf spot or northern corn leaf blight are present, and when hybrids susceptible to these diseases are grown. This scenario is not representative of the typical production field in the Red River Valley, and growers in northwest Minnesota should use caution when interpreting data from such environments. Additional information on corn production from the University of Minnesota is available at: 

http://www.extension.umn.edu/corn

Dr. Jeff Coulter
U of MN Extension Corn Agronomist