In 2016, much of Western Canada experienced cool, wet conditions after seeding, which favours seedling disease development in soybeans.
With soybeans being grown more frequently in rotations, soybean disease inoculum is building up in soil in many different areas. With this and with the right environmental conditions, growers are now beginning to notice more seedling disease and more plants dying off at the time of emergence.
People often call me to say, “I’m using a seed treatment and I’m still seeing seedling disease. Why?” A seed treatment gives you three to four weeks of protection from the date of seeding, but many factors can affect seed emergence, like soil temperature at seeding, planting depth, soil compaction and more. You want your seeds coming out of the ground as soon as possible to realize the maximum value of your seed treatment.
What diseases are the culprit here? Pythium, rhizoctonia, fusarium and early season phytophthora are always a concern. They all look similar when present on plants that are very small. Overall, it’s hard to say what one single disease is on the rise.
When it comes to phytophthora specifically, genetics play a big part. The majority of resistance to phytophthora is based on the seed you choose.
Crop rotation is another big issue. There are more beans-on-beans in some areas because the returns are currently favourable, but over the long term, this can put you at risk of building up disease pathogens more quickly. From a seed treatment perspective, it is important to choose products that have activity on a broad range of disease and insects. And there continues to be new pests along with new innovations in soybeans.
There’s no magic bullet, but with enough knowledge, growers can protect their soybean seedlings as best as possible.