Good Mycotoxin Test Begins With A “Representative” Sample!
The importance of collecting a “representative” sample cannot be overestimated. The most significant variable associated with mycotoxin test results comes from incorrect sample collection or uneven distribution of infected kernels in load (Figure 1). Although taking a sample from the top of a storage bin, truck or combine may be easy and very convenient, you may not be collecting a sample representative of the load since mycotoxin distribution is rarely distributed evenly in a load of corn.
Figure 1 – Variability of infected kernels in a load can impact sampling and testing accuracy!
These two loads both have 5 ppm DON but the distribution of infected kernels are uniform for the left load compared to the load on the right. “Hot Spots” whether in a field or a load can significantly impact the accuracy of sampling and testing for mycotoxins.
The MORE samples the BETTER!
If the sample is from a bin, truck, V-box, or other stationary load of corn, a sample probe (hand or mechanical) is recommended. Although 10 probes are recommended, 5 random probes will do if necessary. Using a “X- shaped pattern will assist in the collection of a representative sample. If you are dealing with a moving stream of grain (end-gate), samples need to be taken from the entire width and depth of the grain stream during the unloading.
Bulk and clean the sample, as well as make sure the sample is uniformly ground in a clean grinder (flour consistency). This will help reduce cross contamination of samples. Mix the grouped sample and take a representative sample from this pooled sample. Regardless of how the sample is taken, it must be processed quickly! Therefore ship or deliver the sample promptly. The longer the sample sits around the greater potential of an inaccurate result.
According to colleagues at The Ohio State University “Air (suction) probes are not recommended for sampling grain with ear rot. Mouldy and broken kernels are lighter in weight and usually contain high levels of deoxynivalenol (DON). Air probes are more likely to pull these kernels and overestimate the overall DON level in the lot.” (https://ohioline.osu.edu/factsheet/plpath-cer-04)
Taking these comments into consideration, one way to ensure collection of a representative grain sample using an air probe is to turn off the air until the probe is closed. The air can be turned on to move the kernels into the test location but only after the probe is closed!
When it comes to sampling and an accurate mycotoxin test – THE MORE SAMPLES TAKEN THE BETTER!
For more information, click on the Crop Protection Network article “Grain Sampling and Mycotoxin Testing” as well as visit the Crop Protection Network Website for further information on field crop related crop protection issues.