Testing wheat seed for fungal disease is important for a few reasons. A basic seed test for germination and vigour will tell you how viable that seed is, but if your germination rate is down, a basic test won’t tell you why it’s down. With low germ, you may have to increase the seeding rate, which increases costs.
By testing for fungal disease however, upping the seeding rate might be avoidable. “You may be increasing your seeding rates based on that low germination but you may be able to address that problem better if you have an idea of what diseases are in that seed,” says Jeremy Boychyn, agronomy research extension specialist with Alberta Wheat and Barley Commissions.
A fungal disease screen that pinpoints disease issues can then help shape management decisions, such as choosing the right seed treatment, or making a more appropriate decision on the seed lot. Sometimes, finding a completely new or different seed source might be necessary.
To send a sample in, follow the same method that you would when sending one in for a germination and vigour test. Make sure it’s a distributed sample that’s representative of your seed lot and submit to a seed testing lab, says Boychyn.
There can be a long list of diseases that might be present in your seed — aspergillus, alternaria, and cladosporium to name a few — and the question is, when do I need to address these diseases? “Knowing which of these fungi are actually affecting germination is going to be important,” says Boychyn.
Fungal diseases can be lumped into three categories: weak pathogens, storage pathogens, and pathogenic pathogens. Some will have an impact on germination, some won’t. The group to be concerned about are the pathogenic fungi.
(Watch the full conversation to learn about the thresholds for damage of the categories, story continues below).
“Look to germination first and say ‘is this germination level where I expected it to be?’ and kind of move through those disease groups, those fungi groups and see where there’s potential issues rising from,” says Boychyn.
All varieties of wheat will hit their peak potential when they’re at their ideal seeding rate — one that results in 28 to 30 plants per square foot — and environment and the germination rate will both affect seeding rate. That seed also needs to be protected with a seed treatment. Even if some of these diseases don’t impact germination, they might be a precursor to leaf diseases later on in the season, says Boychyn.
Remember that different seed treatments will be more effective on different pathogens, so make sure the treatment matches the issue.
Boychyn’s final word of advice? Make sure that seed testing is part of a bigger agronomic program — strong rotation, picking varieties suited to the diseases you see most often, proper nutrient management plan, scouting, and spraying when needed.