Reducing Mycotoxins in Corn Silage with Application of Fungicides

Fungi that infect crop plants and produce mycotoxins can reduce grain quality and profits, but they can also affect the performance of livestock who consume infected feed. There are a number of mycotoxins that can be found in Ontario crops, and the one we discuss most often goes by a few names: deoxynivalenol, vomitoxin or DON. We typically have greater levels of DON when there are cool, wet conditions during pollination and grain fill.

In corn, DON is produced by Gibberella zeae (the name of a specific life cycle of Fusarium) and presence of DON can cause cattle to refuse feed. At DON levels above 0.5 ppm in feed there can be cause for concern of animal health and productivity, and at levels above 2.5 ppm feed containing DON can cause harm to cattle. Livestock may refuse to eat contaminated feed, and research conducted by Pennsylvania State University has shown that at levels as low as 0.56 ppm animal performance can be reduced.

Field Trials with Proline®

A 3 year study was conducted from 2013 to 2015 on farms in Eastern Ontario to assess the use of the fungicide Proline® on corn silage to reduce mycotoxin levels. Proline® was applied at the tasselling stage in plots with 2 replications. Silage weight and moisture were measured, and samples were tested for the presence of the following mycotoxins: aflatoxin (types B1, B2, G1 and G2), fumonisin (B1 and B2), ochratoxin A, zearalanone, T-2, HT-2, 3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol, and DON.

Figure 1: Photo courtesy of John Nanne, Pakenham

Figure 1: Photo courtesy of John Nanne, Pakenham

In each year of the three years, the main mycotoxin present was DON. Other mycotoxins found at minimum levels were 3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol, T-2, HT-2 and zearalenone. Overall, when Proline® was applied there was an average 66% reduction in DON levels and a modest 4% average increase in silage yield (Table 1). Based on corn silage valued at $35/tonne and the cost of Proline® fungicide of $32/ac + $10/ac for application, a 1.2 tonnes/ac silage increase is required to break even. This does not include the value of improved animal performance from reducing the level of mycotoxins.

Note that the fungicide CarambaTM is also registered for use on field corn for suppression of Gibberella zeae.

Table 1. Summary of mycotoxin levels and corn silage yield in untreated and Proline®-treated plots

  Average
DON (ppm)
Reduction of DON Average Yield
(mt/ac)*
Yield Increase with Fungicide
Harvest Year
Untreated
Proline
Untreated
Proline
2013
0.5
0.1
-73%
16.6
17.0
2%
2014
0.5
0.2
-61%
20.5
20.8
1%
2015
1.4
0.5
-65%
18.9
19.8
5%
Average
0.7
0.3
-66%
18.0
18.7
4%

* Silage yield is in metric tonnes per acre adjusted to 65% moisture.

Weather Conditions and Mycotoxins

The weather, particularly the amount of rainfall during pollination and grain fill, impacts the growth of fungus and the mycotoxins they produce. Above normal rainfall in August 2015 may be the reason for the highest DON level over the 3 years, which was recorded in the untreated check. In general, rainfall was normal in 2013 and 2014, resulting in lower DON levels. Figures 1 and 2 show the Percent of Normal Rainfall for the months of July and August in 2015, respectively. The red circle indicates the area where the on-farm trial sites were located.

Figure 1: Rainfall Percent of Normal for July 2015

Figure 1: Rainfall Percent of Normal for July 2015

Figure 2: Rainfall Percent of Normal for August 2015

Figure 2: Rainfall Percent of Normal for August 2015


For more information:
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