Helmut Spieser, Agricultural Engineer, OMAF Ridgetown
Peter Johnson, Cereal Specialist, OMAF, Stratford
Albert Tenuta, Field Crop Pathologist, OMAF, Ridgetown
Weather conditions in 2013 have been ideal for Fusarium Head Blight development in areas of Ontario and surrounding US states. Every year we deal with or try to minimize Fusarium impact on the crop and this year is no exception. How much, and to what extent of course, will depend on variety (susceptible vs tolerant), heading dates, and weather. Growers need to be vigilant and do a pre-harvest scout of the crop.
There is no rescue treatment available to combat the Fusarium that exists now in wheat fields. Careful harvesting, drying and storage strategies are the best way to maximize grain quality. The following information gives our best recommendations to put quality grain in the bin.
– Harvest as early as possible
– Slow forward speed
– Use high wind blast
– Open cleaning sieve settings
– Immediately dry infected grain over 16% moisture in a heated air dryer
When to Harvest
Harvest should begin as soon as the combine is able to thresh the crop (even above 20% moisture). Fusarium growth can continue whenever grain moisture is above 19%. Toxin levels can almost double with one rainstorm (Johnson, 2004). One caveat:: above 18% moisture some combines have difficulty blowing out the lighter Fusarium-damaged kernels. Growers must then make the call to wait and risk further spread or combine, dry and remove small kernels with aspiration.
Harvest Speed
Reducing combine travel speed can reduce Fusarium levels. Slower combining speed reduces the amount of material on the cleaning sieve and allows time to separate the good kernels from the infected kernels.
Fan Speed
Kernels with initial Fusarium infection are small, shrunken and lighter than sound kernels. It is possible to blow a large proportion of these Fusarium-damaged kernels out the back of the combine by increasing the fan speed to deliver an air blast above normal ranges.
Testing at Ridgetown in 1996 found that high fan speeds removed a significant percentage of tombstone kernels caused by primary Fusarium infection (Figure 1). There was a tenfold decrease in Fusarium-damaged kernels in the grain sample when fan speeds were operated to deliver maximum air blast. Operating cleaning fans at these high speeds causes an additional loss of good kernels, up to 2 bushels per acre (0.13 t/ha). This small yield reduction is insignificant if the crop can be made marketable, rather than being downgraded to feed, sample or salvage. To adjust your own combine, start at maximum fan speed and check both the sample and losses (newer combines may be able to blow all the grain out the back). Reduce the fan speed if necessary and again evaluate your harvest sample for Fusarium-Damaged Kernels (FDK). A more recent Ohio study adds support to this result (http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-04-11-0309).
Figure 1 – Effect of different fan speeds on wheat yield
|
Fan Speed (rpm) |
||||
|
1,160 |
1,220 |
1,280 |
1,330 |
|
|
Sieve Setting: (1/4″) |
||||
| Good kernels on ground: (/ft2) |
16 |
31.6 |
35.2 |
43.6 |
| Loss: (bu/ac) |
0.83 |
1.58 |
1.76 |
2.18 |
| Loss at 60 bu yield: % |
1.38 |
2.63 |
2.93 |
3.63 |
Case International 1644, Harus Wheat, EssexCounty, July 17, 1996.
Travel speed 4.2 mph. Rotor speed 880 rpm.
Source: Dr. Art Schaafsma, University of Guelph, RidgetownCollege, 1996.
Chaffer Setting
Consider adjusting the cleaning sieves (chaffer) to a more wide-open setting. This directs the air blast vertically, slowing the rearward movement of the grain mass and aiding cleaning and separation. Caution must be used to keep wheat heads and straw pieces out of the grain sample if the chaffer is opened.
Dry grain above 16% using heat
Fusarium can continue to develop in any grain over 19%. Immediate drying of tough grain arrests further Fusarium development. To maintain milling quality follow the recommendations in Figure 2. The baking quality of wheat is damaged if the temperature of the grain reaches 60°C (140°F). The kernel temperature of the grain is not the same as the plenum temperature of the dryer. Kernel temperature can be measured by putting a sample of grain in a steel can and placing the thermometer in the centre of the sample. When heated air dryers are used, it is a worthwhile precaution to have samples evaluated to ensure the dried grain meets market standards.
Figure 2 – Maximum Recommended Air Temperatures for Drying Milling Wheat1
|
Maximum Temperature |
||
| Dryer Type or End Use |
ºC |
ºF |
| Non-recirculating batch dryers |
60 |
140 |
| Recirculating batch dryers |
60-70 |
140-158 |
| Cross-flow dryers |
60 |
140 |
| Parallel-flow dryers |
70 |
158 |
| Seed Wheat |
40 |
104 |
1Copyright: Farm Drying of Wheat, Canadian Grain Commission, Sept 1992
2Wilcke, William F., Hellevang, Kenneth J. Wheat and Barley Drying, FS-5949-GO, 1992. University of Minnesota, Extension Service