WOOSTER, Ohio – With wheat harvest now under way in Ohio, sampling and testing for vomitoxin in head scab-infected wheat is vital to prevent further losses and avoid potential health problems in humans and livestock.
Pierce Paul, an Ohio State University Extension plant pathologist and small grains specialist, said that grain elevators will likely be testing every lot to ensure that any vomitoxin in infected grain stays below the acceptable limit of 2 parts per million.
"It's important that the testing be conducted correctly to avoid overestimating or underestimating vomitoxin in the grain," said Paul, who also holds a research appointment with the Ohio Agricultural Research and Development Center.
Wheat in some portions of Ohio is experiencing upwards of 60 percent incidence of head scab – a disease that attacks the wheat during flowering under wet, humid conditions. The disease can impact yields. In addition, the fungal pathogen that causes head scab produces several mycotoxins, including vomitoxin, that affect grain quality. Feeding infected grain to livestock can be harmful, and using infected grain for bran, flour and germ can be unhealthy for human consumption.
Wheat growers throughout southern Ohio are now harvesting their wheat and growers throughout central and northern Ohio are on tap to begin harvesting their wheat within the next week or so. Now is the time, said Paul, to sample grain from fields either known or suspected to be infected with head scab and test for vomitoxin levels.
"In a nutshell, growers should pull multiples samples from their grain load, grain stream or grain truck, and send the grain to a certified vomitoxin laboratory for testing," said Paul. "The tests can then help growers decide whether to market the grain, blend the grain, feed to animals, or dump the grain entirely."
To reduce the amount of scabby kernels and level of vomitoxin in wheat grain and to avoid potential health problems for combine operators and grain handlers, Paul is encouraging growers to follow the recommended tips when harvesting wheat:
• Turn up the air in the combine to blow out scabby kernels. Scabby kernels are usually lighter in weight than healthy kernels and will be blown out the back of the combine. This reduces the amount of scabby kernels and vomitoxin in the grain lot.
• Harvest areas of fields with the most scab first and keep that grain separate from the rest of the crop.
• If rain is in the forecast leading up to harvest, harvest scabby fields at a slightly higher moisture content rather than waiting for grain to completely dry down in the field. Doing so prevents additional vomitoxin build-up in the grain. However, the grain still needs to be dried down in the storage bin to prevent further fungal growth and vomitoxin build-up in storage.
• Wear gloves if handling infected grain and wear a dust mask while harvesting infected grain to avoid contact or inhalation.
• Always have grain from scabby fields tested for vomitoxin before feeding to livestock. For grain and grain by-products destined for consumption by ruminating beef and feedlot cattle older than 4 months, and chickens, the limit is 10 parts per million. Ingredients with 10 ppm should not exceed 50 percent of the diet. For grain fed to swine, and all other animals, the limit is 5 ppm, with the limit not exceeding 20 percent of the diet for swine and 40 percent of the diet for all other animals.
For growers considering tearing wheat out and planting soybeans, eliminating the wheat stubble is important.
"The disease can pose a risk for this year's corn crop and next year's wheat crop. The scab fungus can even remain in soybean residue, so carrying that pathogen over from one crop season to the next is a big risk," said Paul.
Paul said that some Ohio growers with high levels of scab in their fields face a tough decision as to whether to tear up wheat and put in a late-planted soybean crop, or keep the wheat crop and hope that any grain with vomitoxin can be blended with healthy grain to bring the vomitoxin contamination down to acceptable levels.
"If a grower has high levels of Staganospora and head scab in the same field, and the yield target was 70 or 80 bushel wheat, that target might now be half of that. Even if you get decent yields, but the vomitoxin levels might be so high that the grain is rejected, then what does the grower do?" said Paul. "It's a Catch-22."
The latest information on head scab in Ohio can be found at the OSU Extension Agronomic Crops Network at http://agcrops.osu.edu. A list of vomitoxin-testing laboratories can be found at http://www.oardc.ohio-state.edu/ohiofieldcropdisease/wheat/mycotoxin%20text2.htm.