Producers should be on the lookout for fusarium head blight this year, even though the incidence of the fungal disease was down in 2017.
“Forecasting head blight is really quite challenging,” said Mike Harding, a research scientist and plant pathologist with Alberta Agriculture and Forestry.
The province saw record levels of fusarium graminearum in 2016 because it was a wet year. The extremely dry conditions last summer reduced the incidence but the pathogen continues to spread to new areas, and there is more of it in areas that have already been infested.
“We can’t say that it is necessarily established everywhere, but it certainly is spreading,” said Harding.
Fusarium species are very adept at colonizing cereals and corn at the ground level, particularly in the first node of the plant, where the largest number of pathogens are found. Some of the pathogens that cause head blight produce asexual spores that can splash higher up on the plant when it rains. These spores then infect the anthers, grow down into developing kernels, and cause shrunken, bleached kernels.
“In years where we don’t see a lot of head blight, it doesn’t mean that the fusarium has gone away,” said Harding. “It just means that the fusarium may be present low down in the canopy or even on the roots.”
The pathogen could simply have been completing its life cycle down in the crop in 2017. As a result, producers should be on the lookout in any area where fusarium graminearum is common.
In 2017, there were dry conditions in south and central Alberta during the flowering period, and a survey by the Canadian Grain Commission showed that numbers were down.
“The weather influences this disease to a great extent,” said Harding, noting the highest risk is when there are wet conditions during the flowering period.
Even if the disease wasn’t seen in 2017, it could still have colonized crop residues.
“Just because we had low levels in 2017 doesn’t mean we couldn’t have another record-breaking year in 2018,” said Harding.
Fusarium graminearum head blight has been most common and damaging in southern Alberta, but a 2016 survey by Alberta Agriculture found 20 per cent of all the fields on the eastern side of the province had some signs of the pathogen. There are also a few pockets in other areas of the province and researchers found their first positive sample in the Peace in 2016.
“There are some areas where it is more severe and we expect to see a significant number with more than 20 per cent of fields with it in a wetter year,” said Harding. “But every field in the province needs to be on alert for this. It’s probably not going to stop moving.”
By the time symptoms of head blight have been found, there are no management options left. But it’s still good to scout during the late-milk to early-dough stage to look for signs of prematurely ripening florettes.
“Sometimes, even when you peel back or look around the edge of the bloom, you can see a pink or salmony-coloured growth of the fungus,” said Harding.
At harvest, producers will see shrivelled and bleached kernels.
In order to prevent the spread of the pathogens, producers should test their seed, and avoid bringing contaminated or infected seed onto their farm.
“Because fusarium is surviving on crop residue, crop rotation is a good management tool,” said Harding.
Other tips include using high-quality seed, seed treatment, purchasing good genetics, applying fungicide, and increased seeding rates.
This year, Alberta Agriculture has also developed an app that can be used on a computer or mobile phone. The app, which can be found at weatherdata.ca/m calculates hourly risk, and also offers weather alerts and historical fusarium data.
Producers should check it daily because the situation can change from day to day, said Harding. The site is only active during the growing season.