Written by Bob Fanning, former SDSU Extension Plant Pathology Field Specialist.
South Dakota corn producers may want to scout their fields for ear molds. High humidity and dew during the night, accompanied by hot, dry conditions during the day are ideal for ear molds in corn which have the potential to produce mycotoxins. Fortunately not all molds on corn form mycotoxins. Aspergillus spp. and Fusarium spp. may produce toxins of concern, while other fungi such as Penicillium and Diplodia are usually harmless, esHecially if grain is generally intact and undamaged physically.
Aflatoxins are highly toxic to livestock, poultry, and people. Even when fed at nonfatal levels, aflatoxin can seriously impair animal health and productivity. For lactating dairy cattle, do not exceed 20 ppb aflatoxin in rations to avoid exceeding the Food and Drug Administration level of 0.5 ppb in milk. Aflatoxin is just one of many mycotoxins that can adversely affect animal health and productivity.
Scouting for ear molds can be started as early as the R6 stage, or physiological maturity. The stalk of the plant at this growth stage may remain green, but leaf and husk tissue has lost its green color. Kernel moisture content ranges from 30-35% at this point. The recommendation is to check 100 ears of corn from several different places within the field. If more than 10% of the plants have ear mold, it may be beneficial to harvest the field early and dry the crop. If you think your crop has been damaged by aflatoxin, notify your insurer before harvesting. Aflatoxin contamination should be covered as long as representative samples of grain were taken before the grain was moved into commercial or on-farm storage. Crop insurance generally ends at harvest, so it is important that your insurer samples the crop before it is moved into storage.
Mycotoxin-producing ear molds can be present and not easily seen on corn ears. Carefully examine the husks as you remove them and look closely at and between the kernels for signs of molds. Grain should be dried to below 15% moisture, but to ensure stopping mold growth, dry the grain to as low as 12%. Dry and cool the harvested corn quickly, preferably within 24 hours of harvest. The goal is to reduce the moisture level as quickly as possible to help prevent more molds from forming on the grain. This is especially important if corn has been harvested early and has a moisture content that is higher than recommended for safe storage. Livestock producers should test any moldy corn for mycotoxins before feeding it.
Mycotoxin management at the time of harvest involves optimizing harvest and storage conditions to minimize physical damage and avoid additional mold growth . Storage at a cool temperature will also help to slow down fungal growth in grain, and gentle handling will limit the amount of damaged grains which are a source of nutrients for fungi in storage.
For more information, access:
- Aflatoxins: Hazards in Grain/Aflatoxicosis and Livestock
- Dealing with Mycotoxin-contaminated Feeds at Feeding Time
- Managing Change in Livestock Production Mycotoxins in Feed
- Best Management Practices for Corn Production in South Dakota - Chapter 9: Corn Diseases in South Dakota (pages 66-68) - Paper copies of these publications can be obtained at your closest SDSU Regional Extension Center.
Producers wishing to have their grain or feed to be used for animal feeding operations tested can send samples to:
SPSB 153, Box 2108
Brookings, SD 57007
- Services offered: aflatoxin, fumonisin, zearalenone, deoxynivalenol (DON) screens
- $35 for sample prep and first compound.
- $15 for each additional compound on same sample.
NDSU Van Es Hall
1523 Centennial Blvd
Fargo, ND 58102
- Services offered: multi-mycotoxin screen (aflatoxin, vomitoxin, tricothecenes)
- $ inquire for costs