The 2010 cool, wet growing season was a contributing factor to a dramatic increase in ergot in wheat and barley last year, but the real cause is likely due to a nutrient deficiency, says an Alberta-based plant pathologist.
If plants are low in copper, pollen can be sterile, says Ieuan Evans, plant pathologist and senior agri-coach with Agri- Trend Agrology. And if wheat and barley don’t self-pollinate, their flowers will open which exposes them to ergot infection. Complicating the matter, cool, wet weather favors ergot germination so there are more disease spores floating in the field.
Evans, who has long-championed the value of copper in cereal crop production, says there are other circumstances when wheat and barley, in particular, can be affected by ergot. Research has shown under very hot conditions at flowering the pollen can essentially “cook,” forcing the plant flowers to open and be exposed to disease spores. Also, there have been reports of higher rates of ergot developing if crops are exposed to frost at flowering. And other research has also shown that even hail at flowering can predispose flowers to open and be exposed to the disease.
“But ergot related to very hot conditions, frost and hail are very rare, and may occur one to two per cent of the time,” says Evans. “The bulk of ergot in wheat and barley is caused by copper deficiency.” This does not apply to rye and triticale, for example, since they are open-pollinated crops and are more readily exposed to ergot.
In a cool, wet year, there is more ergot germination in a field, says Evans. Under wet conditions, in fields where there is plenty of crop residue or high organic matter content in the soil, the conditions stimulate the activity of soil microbes, bacteria and fungi.
“We have all this increased activity of bacteria and soil microorganisms and as they go to town on crop residue they tie up several nutrients, particularly in the top six inches of soil,” says Evans.
“And in a wet year, plant roots don’t have to penetrate deeply to reach moisture so crop roots stay near the soil surface as well. Many of the nutrients, including copper, are tied up, the roots stay shallow, and that leads to a copper deficiency in the plant.”
In a drier year, crop roots penetrate more deeply into the soil and can reach nutrients further down.
Since copper is important to healthy, vital pollen, in a deficient situation, the pollen is sterile or weak, wheat and barley can’t self pollinate, so the flowers which normally stay closed once the head emerges, open as the plant searches for pollination, exposing it to ergot spores.
Evans’s research has shown that adding supplemental copper under wet conditions can reduce ergot and dramatically increase crop yields. “It can mean the difference between having a 60-bushel crop or a 90-bushel crop,” he says.
“I have worked with many producers in the Parkland County north of Edmonton, where they can often have higher-moisture conditions,” he says. “There were many cases where farmers complained about 30 and 40 bushel yields, high levels of ergot, and grain that graded No. 3 or sample. But now more are adding copper, yields have jumped to 70 and 90 bushels and they have no ergot. It is totally copper related.”
Evans says 20 per cent of western Canadian soils are known to be copper deficient, even in average years, so under widespread wet conditions available copper is tied up over a much larger area.
He says it is important for farmers to complete soil tests to determine copper levels, and particularly under wet conditions, he recommends a top dressing with a foliar copper treatment to ensure the plant has proper nutrients to produce healthy pollen.
In a related matter, Evans also contradicts a common belief that too much cow manure will cause crops to lodge because of excess nitrogen. “It isn’t a case of too much nitrogen, it is related to a lack of available nutrients such as copper,” he says. “If you put high rates of cow manure on sandy soil, for example, it again stimulates the soil microbes and micro organisms and it is that increased activity which ties up nutrients such as copper.”
Again he says top dressing with a foliar application of copper and other micro nutrients will help to correct the nutrient imbalance.
LeeHartisafieldeditorforGrainewsat Calgary.Contacthimat403-592-1964orby emailat [email protected]