Testing wheat for DON levels
Fusarium head scab is severe enough to lead to wheat from some fields being discounted for DON upon delivery. Growers may choose to have the grain tested prior to delivery or storage.
As wheat harvest is finally getting underway, a quality deterrent called DON (or vomitoxin) is being confirmed by tests run on early harvested wheat. This is a concern for growers as discounts are imposed when the DON exceeds approximately 1 ppm for soft white wheat and 2 ppm for soft red.
DON is a naturally occurring mycotoxin that is a by-product of a naturally occurring wheat disease called Fusarium head scab. The symptoms of scab have been evident in fields across Michigan. The disease, and the resulting DON level, is usually highest where growers use a particularly susceptible variety, seed wheat following corn, or do not use a fungicide soon after heading.
Most grain elevators test truck-loads of wheat as they are delivered. Many of them are also willing to test samples for growers. However, growers may want to have their grain tested by an independent laboratory for the purpose of developing a marketing plan, meeting crop insurance requirements or segregating wheat into separate storage bins.
It takes a significant effort to obtain a reasonably representative grain sample because DON levels tend to be highly variable across fields of wheat and within bulk loads of grain. In addition, the test is highly sensitive so even a single kernel or a little chaff can contaminate a sample and affect test results. To sample a truck-load or grain bin of wheat, Michigan State University Extension recommends:
- Using a grain probe, take a minimum of 12 probes from different locations in a bin or at least 5 probes from different areas within a truck load. Collectively, these subsamples should generate approximately 10 pounds of grain.
- Thoroughly mix the 10 pounds of grain and extract a composite sample weighing one to three pound depending on the number of tests being requested. Consider extracting a second sample to have the option of additional testing in the future.
- Dry the grain to approximately 13 percent moisture to avoid having the DON level potentially increase during shipment or, at the very least, cause delays in processing.
There are several public and private laboratories that offer DON testing. Two of the laboratories that can offer an official USDA GIPSA certificate are MI Grain Inspection Service and USDA GIPSA FGIS. Instruction for each follows.
MI Grain Inspection Service: A private laboratory certified by USDA near Mason; if using FedEx or UPS carrier, mail sample to: MGIS, 118 East Michigan, Marshall, MI 49068; if using the US Post Office, mail sample to P.O. Box 465, Marshall, MI 49068; their telephone number is 269-781-2711; the cost for DON testing is $26.50 per sample; [a full grade determination can be made for additional $9.50; Falling number testing is not available]; make checks out to MI Grain Inspection Service.
USDA GIPSA FGIS: A USDA facility in Maumee; if only requesting DON test, send at least one pound sample of grain to USDA GIPSA, 1910 Indian Wood Cir. Suite 401, Maumee, OH 43537; their telephone number is 419-893-3076; the cost for DON testing is $42.30 per sample;. [If additional tests are desired, send a three pound sample; a Falling Number test is an additional $21.05; an official full grade determination is an additional $13.20]; make checks out to USDA GIPSA FGIS.
The one or three pound composite grain sample should be placed in a paper bag (not plastic) and then an appropriate shipping box. Also enclosed, should be a check to cover the cost of the tests and a sheet of paper providing the prompts and responses given here:
Wheat tests requested
Sample’s identification name or number
Farm or personal name
Farm mailing address
Both laboratories prefer to email the results and certified report to the sender. Test results are often available a couple days after the sample is received by the testing facility.
The author gratefully acknowledges Lynn Thomas, Field Office Manager, USDA GIPSA, for reviewing this article.