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Competency Area 3: Management of Infectious Plant Diseases

PO 26. Know strategies for minimizing contamination of commodities by mycotoxins.

Greatest mycotoxin risk factors in corn production:

  • Moist weather at silk emergence (Gibberella ear rot; deoxynivalenol and zearalenone)
  • Drought, high temperatures during grain maturation (Fusarium and Gibberella stalk rots; Fusarium ear rot; fumonisins)
  • Insect or other mechanical damage to ears or stalks
  • Delayed maturation/delayed harvest
  • Contaminated storage structures
  • Failure to adequately dry grain or poor ventilation of dried grain storage
  • Failure to exclude air from high moisture, anaerobic storage

Field practices that reduce the risk of mycotoxin contamination in corn:

  • Timely planting of locally adapted hybrids of appropriate maturity with partial resistance to Gibberella ear rot
  • Avoiding continuous planting of corn under conservation tillage, especially where Gibberella/Fusarium stalk rot is prevalent
  • Fertilizing based on soil test and avoiding excessive nitrogen
  • Avoiding stress from insects, weeds, and excessively high plant populations
  • Planning ahead for harvest and subsequent grain handling:
    • Clean grain bins before putting in the new crop
    • Harvest fields with delayed maturity or high lodging potential as silage or grain for anaerobic storage; or be prepared to rapidly dry grain down to 13.5% moisture content
    • Aerate grain bins to prevent moisture migration caused by colder temperatures
    • Harvest silage at recommended plant maturity, and pack well to eliminate air pockets

Testing for mycotoxins
On-site test or laboratory test?
On-site test kits are available through commercial firms. Most are antibody-based and indicate contamination by a color change; other tests utilize thin layer chromatography (TLC) or minicolumns. On-site tests are quick and relatively inexpensive (depends on the number of samples run). They generally give accurate and reproducible results when used on dry grain samples; they are not as reliable for high moisture grain or silage. Specific mycotoxins can be quantified relative to standards that are supplied with the kits. On-site tests are often used as diagnostic tests prior to confirming laboratory tests. Commercial and government/university labs offer mycotoxin testing. Lab tests are expensive, comprehensive, and quantitative for many toxins, and are useful for wet and dry samples. Methods include high-pressure liquid chromatography (HPLC) and gas chromatography-mass
spectrometry (GC-MS). 

Sample collection and handling
Samples must be representative of grain in a truck or bin or silo. Obtain many small samples at periodic intervals from a moving stream of grain or by probing all levels and areas of a stationary grain mass to make a composite 10 lb sample, which should be further mixed and subsampled to produce a 2 lb sample for shipping to a lab. Ship dry samples in breathable cloth or stout paper bags. Wet samples should be in sealed containers and be frozen or refrigerated during transit.