Don’t blame ergot on the weather

Copper deficiency leads to the development of many diseases in cereal crops

When we have years with lots of ergots, we have higher levels of wheat midge.

If you’re a pedigreed seed grower and you’ve discovered that one of your seed fields, either wheat or barley, is infested with ergot, you have a problem but it’s not what most, if not all of you think. Don’t blame it on a common diagnosis of cold, wet growing conditions. It’s more likely caused by a soil fertility issue — a plain and simple copper deficiency.

Ergot in wheat, barley or oats

The presence of ergot in wheat, barley or even oat seed is a sure-fire confirmation that you have some copper deficiency in your cereal cropland. When ergot shows up in these normally closed pollinated seed crops, it’s a sign that low to very low soil-available copper levels result in pollen sterility in these cereal crops. Pollen sterility causes these normally closed cereal flowers to open up in order to pick up stray cereal pollen from surrounding plants or surrounding cereal fields.

Once the flowers are open, if ergot spores show up you end up with ergots on the open, pollen-free flowers (stigmas) instead of grain. At that point, if pollen from within the crop or from the next field shows up you will have normal grain. But if pollen from an adjoining wheat or barley crop of a different variety appears, you’ll have sure fire cross pollination, bread wheat pollinated by utility wheat or malt barley pollinated by feed barley. If neither pollen or ergot shows up you have got blanks and a yield loss since grain is not formed.

If ergots are present in seed wheat or seed barley kept over for crop seeding, don’t worry. Since the ergots did not get wet and vernalize in the soil over winter they will not germinate in the coming spring.

It has been frequently correlated that when we have years with lots of ergots we have higher levels of wheat midge. That is, the midge can lay more eggs in open, copper-deficient wheat flowers. Some scientists have also observed higher levels of fusarium in copper-deficient wheat fields since normally closed flowers open up.

Weather and soil

Cool, cold or rainy weather and so-called prolonged wheat flowering (closed flowers) have nothing directly to do with ergot infection. What really happens is that in wet seasons we have much shallower rooting of wheat and barley. You have farmed the land for 100 to 200 years. As a consequence, you have removed about one ounce (30 grams) of copper per acre per year, particularly from the top six to eight inches (15 to 20 cm) with each crop. Remember there were only two to three pounds of actual copper mineral in the topsoil of an acre. So over 100 years at a removal rate of one ounce of copper per acre you could have removed 100 ounces or more than six pounds of copper per acre.

In dry years the wheat or barley roots move into the subsoil where they can still access adequate copper in most soils.

Light sandy soils are the most likely soils to become copper deficient due to poor nutrient holding capabilities.

Peat soils and soils very high in organic matter sequester or tie up copper. In Bradford (Holland Marsh) north of Toronto, horticulturists add about 150 pounds of copper sulphate (bluestone 25 per cent copper) per acre to the soil over three years, which will meet crop needs for 20 years or more. This fixes the copper need and they grow some of the best vegetable crops in Canada. Similarly, the high organic soils in the Barrhead/Westlock area of Alberta respond remarkably to generous copper amendments in both yield, quality and absence of ergots.

Copper and lodging

When you add cattle manure to soil, particularly light soil you get severe crop lodging. Too much nitrogen, you say? Nonsense. The nitrogen becomes limiting due to a high carbon ratio causing a surge in soil microbiology (bacteria, fungi, worms) and a tie-up of copper needed by these organisms. The cereal crop lodges due to copper deficiency. Low copper levels cause crop lodging because two copper-based enzymes are necessary for straw strength. Good soil copper levels mean strong standing straw and plump grain.

Some herbicides, particularly the Group 1 fop types, interfere with copper in cereals and can result in moderate to severe lodging. If you see lodged wheat crops but the wheat is standing in the sprayer tracks then you can bet that the herbicide has interfered with copper uptake. The spray track wheels have crushed the cereal plants and greatly reduced the herbicide uptake. Change your herbicide and pay attention to your soil copper levels.

Copper deficiency

Low copper levels in some soils may not be low enough to influence final yields but they can delay maturity of the cereal crop by five to 15 days — critical in years of late-summer frosts. Under severe copper deficiency, such as in high peat or sandy soils, an expected 70-bushel crop of wheat, particularly in wet years can result in 15 to 30 bushels of sample wheat infected with ergot.

Its time that we faced scientific facts. A significant percentage of Canadian and U.S. soils have become depleted in copper. Lodging, low yields, inferior quality, grain cross pollenating and ergot infestation are a consequence. Remember there are still individuals out there who believe that the earth is flat and the U.S. space mission did not land on the moon.

Soil tests, ergots or unusual crop lodging will let you know if copper is deficient in your cropland. Soil copper amendments can be in-row, broadcast or foliar to achieve your target yields.

About the author


Dr. Ieuan Evans is a forensic plant pathologist based in Edmonton, Alta. He can be reached at [email protected]

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