Green dust a problem
Some Saskatchewan farmers have noticed clouds of green dust emerging from the backs of the combines with some settling on the cutting bar.
This green cloud is usually composed of spores from non-pathogenic fungi growing on stems and leaves in the swath, said Michael Celetti, plant disease specialist with Saskatchewan Agriculture.
“In contrast to the pathogenic fungi that attack green and growing plants, these particular non-pathogenic fungi colonize mature or dead plant material. They’re actually the good fungi, as they contribute to the breakdown of the straw,” said Celetti.
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“But they also colonize early maturing crops affected by drought, stem-bore insects or root-rot diseases. A rain or period of heavy dew prior to swathing or when the grain is lying in the swath provides an ideal environment for extensive colonization by these fungi.”
Celetti said the fungi can give a dirty appearance to the mature crop, but don’t appear to affect grain in the swath.
However, in bins with moist grain, they can cause spoilage.
“Moist, contaminated stored grain may become discolored, rancid, bin-burned or heated. It may have an off-odor, or the germination may be reduced. Some of the fungi can also produce mycotoxins in stored grain. All of these quality losses are regarded as a downgrading factor in the Canada Grain Act, and result in reduced value of the stored grain,” said Celetti.
Total loss
Spoilage in the bin is usually confined to moist hot spots. Unaffected grain can be salvaged but without proper care, whole bins can be lost.
Grain is often contaminated by more than one species of several fungi during combining. Each species can germinate and colonize the stored grain under different environmental conditions: some grow during low temperatures, while others grow under low seed moisture, which results in the production of moisture and the encouragement of more harmful organisms to colonize and contaminate the stored grain.
“Warm, moist grain going into storage will allow the harmful toxin-producing fungi to begin colonizing the grain in storage almost immediately. Proper storage of dry seed is the best method of reducing the potential of grain spoilage,” said Celetti.
Seed should be put in bins during cool days at a moisture content of at least one percent below the maximum level for straight grade seed for that crop. A list of maximum moisture levels for each crop is available in the Canadian Grain Commission grain grading manual.
Weatherproof bins should be used and moist weed seeds and plant debris should be removed or spread evenly throughout the stored grain to prevent hot spots from developing.
Keeping the bin seed cool by continuous aeration and drying will also reduce the potential of storage fungi spores from germinating and developing on the stored grain. Hot spots in the stored grain should be turned to cool and dry the grain.
– Saskatchewan Agriculture
