Ergot lives in the soil, but its viability is drastically reduced after two years. Avoid planting a cereal on cereal stubble to sidestep an infection.
If you’re planning to use infested grain as seed, have it cleaned using a gravity table or colour sorter, or avoid using it for a full two growing seasons, as the ergot bodies will be less viable over time. Using infected seed is never recommended, however.
Mow ditches and headlands to reduce transmission from grasses to the standing crop.
If you notice ergot in the field margins, harvest and store the first few passes separately to avoid downgrading the entire field.
A healthy, evenly maturing stand is your best defense against an ergot outbreak. Chronic copper deficiency makes plants more susceptible to the disease.
Ergot is nearly always there at some level. This common grass and cereal disease is polite enough most years to stick to the headlands and leave wheat and barley well enough alone. But some years, such as 2008, a cool spring and an uneven crop can mean an outbreak of this quality-and yield-robbing disease in rye and other cereals.
Ergot is a soil-borne disease that cruises below the radar for good reason. Most years, headland grasses are the only crop flowering at peak infection time. Wheat is also a self-pollinating plant, and is usually already pollinated when its florets open, making it immune to ergot infection. But if for whatever reason wheat or barley is flowering for an extended period of time or if those florets are sterile at the time of opening, ergot infection can occur.
“Any number of plant stresses can lead to sterile florets,” says Doug Penney, a soil scientist now retired from Alberta Agriculture. “Herbicide injury or a nutrient deficiency are two common causes.”
Copper is often singled out as playing a key-role in preventing an ergot infestation. Penney explains that copper is critical to the development of pollen. A deficiency of the element can lead to deformed pollen and therefore sterile florets. Not only will a grain kernel not form, but the sterile floret is also then susceptible to ergot spores infecting the floret. Rye is so susceptible to ergot because it is mostly open pollinated, meaning that florets are unfertilized when first opened.
LOW GRADING TOLERANCE FOR ERGOT
Farmers who had ergot pressure last year learned just how few ergot bodies it takes to drop a grade. “Tolerance for ergot bodies in a sample is very low,” explains Faye Dokken, provincial plant disease specialist with the Saskatchewan Ministry of Agriculture. The ergot level threshold (as a per cent of net weight for CWRS wheat) are: 0.01 per cent for No. 1, 0.02 per cent for No. 2, 0.04 per cent for No. 3 and No. 4, and 0.1 per cent for feed.
The issue with ergot is what’s contained in the black seed-shaped body. “Ergot bodies contain alkaloids that are toxic to both humans and livestock,” Dokken says. So toxic in fact that there’s even a disease named for consuming food made from ergot-tainted flour: ergotism. Ergotism was rampant in the Middle Ages due to the higher consumption of rye-based bread. The disease, which causes hallucinations, skin tingling and dry gangrene, has been given as a possible explanation for the Salem witch hunts. “Humans are very susceptible to ergotism, and so are animals. The tolerance levels for ergot are incredibly low,” she says.
The telltale black ergot bodies grow in the place of the seed. They are roughly the same size and shape of a grain kernel and so usually can’t be separated by size. A gravity table usually does the trick, as will a colour or optical sorter, if available. But Dokken recommends that your “separating” begin at harvest. Ergot infestations are usually highest at field margins. Spores are usually carried on insects that rarely stray far in field.
By harvesting and storing the first few hundred feet of the field margins separately, you can avoid downgrading of the entire field. The remainder of the field should be relatively clean.
If you know you’ve got ergot in the ditches and headlands, mow them down, especially in a cool, wet year when wheat and barley crops are more likely to have had a rough start to the growing season, Dokken says. Scout for the disease in the field margins, and harvest accordingly. There are no spray options for ergot, Dokken adds, making prevention and cultural management your only options. “Fields with heavy pressure last year shouldn’t be seeded with rye, wheat or barley this year,” she says. Fields adjacent to infected fields may have higher pressure, too.
“Healthy plants and an evenly maturing wheat or barley crop is your best defense against ergot,” Dokken says. Optimal seeding density and depth make a difference, as does using clean seed. “Infected grain from last year shouldn’t be used as seed this year as the ergot bodies are viable for up to two years,” she says. Cleaning the grain is a second-choice option, but simply waiting until 2010 to use infested seed may decrease the chance of infection. That said, clean seed should be your preferred seeding option.
SHOULD YOU APPLY COPPER?
As for ergot’s link to copper deficiency, both Dokken and Penney agree that avoiding an ergot infestation isn’t reason enough for a foliar
It doesn’t take much ergot to drop your grade from No. 1 down to feed.
copper application. That said, copper deficiency can have devastating affects on yield and quality, meaning there is economic justification for copper application on deficient soils regardless of ergot pressure.
Penney adds that copper deficiency occurs most frequently on sandy loam and light loam textured soils in the black soil zone.
“The frequent occurrence of ergot in an area is a reason to suspect copper deficiency,” he says. “Soil and tissue tests can be used to help diagnose copper deficiency pressure.” Copper is highly immobile in the soil and depends heavily on moisture for availability. “It’s important to test not only the first six inches of soil, but also the subsoil copper levels. Copper is needed later in the growing season and if the top few inches of soil are dry, the crop will depend on deeper sources at the critical flag leaf stage,” Penney says.
Lyndsey Smith is a field editor for Farm Business Communications.