Grain Quality Task Force # 25
The 1995 pre-harvest survey of ear rots and mycotoxins in Indiana corn was completed. As in past years, two samples of five ears were collected by the Indiana Statistics Service from each of their field plots located around the state and sent to Purdue University for evaluation of ear rots and mycotoxins. Due to the late planting of the crop this year, we collected samples at or near the time of harvest. We examined 314 samples from 167 corn fields for a total of 1570 ears. Each ear was individually examined for ear rots. The incidence and severity of the following ear rots were determined: Fusarium ear rot (Fusarium moniliforme), Gibberella ear rot (Gibberella zeae), Aspergillus ear rot (Aspergillus flavus), Diplodia ear rot (Diplodia zeae), and minor ear rots (Trichoderma sp., Alternaria sp., Penicillium sp., etc.).
Data from the survey support field observations made during the season of widespread occurrence of Fusarium ear rot. Over 90 percent of the survey samples were positive for Fusarium ear rot. This level is statistically comparable to the 1989 and 1993 surveys which recorded 89.9 percent and 88.6 percent, respectively. This year's disease severity levels were low. We attribute the lower severity to the continued dry weather throughout this harvest season. In the surveys from previous years, samples having disease severity of 10 percent or greater were tested for mycotoxins. This year, samples with severity ratings of 3 to 10 percent were also included. Fumonisins were found in all 18 samples tested, ranging in concentrations from 0.25 ppm to 14 ppm.
This is the first year since the ear rot survey began in 1989 that we have not detected Gibberella ear rot by visual inspection. However, our mycotoxin data indicate that the Gibberella ear rot mold was present in some of the ear samples. Two of the ear samples visually scored as Fusarium ear rot and tested for mycotoxin had fumonisin, the mycotoxin associated with Fusarium ear rot, and vomitoxin (2 ppm and 3 ppm), indicating that both molds were causing the ear rot. The less amount of Gibberella ear rot is likely due to the hot, dry weather this summer.
We observed Aspergillus ear rot earlier this fall in southwest Indiana. The disease incidence was low in the fields and confined to fields with sandy soils. No samples with Aspergillus ear rot were found in this year's ear rot survey.
The data from this year's survey are a good indicator of the post-harvest grain quality. Our data suggest that Indiana grain quality is good. The survey suggests that the levels of fumonisin in corn should not be unusually high. However, the widespread occurrence of Fusarium ear rot suggest that isolated fields will have significant amounts of disease and the mycotoxin. Earlier this fall, horse owners and handlers were advised of the potential for fumonisin in this year's corn.
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