SDS Scouting 101

Tuesday, June 28, 2016
By: Dr. Daren Mueller, Iowa State University, Assistant Professor and Extension Plant Pathologist
Soybean leaves infected with Sudden Death Syndrome

How do I know if I have Sudden Death Syndrome in my soybeans? Where do I start? How do I spot it? When is my crop susceptible? Soybean growers have questions about this prominent disease and we’ve got answers. We’ve got the basics in our SDS Scouting 101 guide.

Scouting Sudden Death Syndrome Q&A with Daren Mueller:

Why is it important for growers to scout for Sudden Death Syndrome (SDS) in their soybean field?

First, there are several other diseases that look like SDS, especially if you are driving past the patches and not getting into your field.

The two main look alike diseases, at least in Iowa, are Stem Canker and Brown Stem Rot (BSR). We have seen an increase in incidence of both of these diseases, but especially stem canker.  Knowing the cause of the problem in a field will help you make decisions (cultivar selection, seed treatment use, crop rotation – if possible, planting order of fields, etc.) for future years. 

What is the optimal timing to scout fields for SDS?

During the mid-to-late reproductive growth stages is the ideal time to start scouting for SDS. I usually start taking notes in mid-to-late August. You can find it earlier and if you just want to know if it is there or not – early September is usually a bit cooler. The key is to get out there before plants begin to senesce – or begin to deteriorate.

When scouting for SDS, what symptoms should growers look for at various growing stages?

Depends on why you are scouting – if you just want to know where it is in fields – then you can just go out once. If you want to know when it first appears and how severe it is across the season – then you will need to get out a few times. If you are looking at different cultivars or seed treatments, then I would recommend getting out a few times because resistance or effective seed treatments may not prevent disease development, but may delay symptoms onset.

What techniques should growers utilize when scouting their fields for SDS? Are there specific steps growers should take to ensure their scouting is effective?

Get into the field and into the patches of diseased plants. Make sure to split the stems to distinguish from BSR and look at the pattern on the leaves to distinguish from stem canker. You should also be scouting for soybean cyst nematodes (SCN) – you don’t need SCN to get SDS – but it certainly doesn’t help. It is always good to manage SCN, so if you find SDS, this should be an excuse to revisit how you are managing SCN as well.

What should growers do if they discover SDS while scouting?

Spend time figuring out what cultivars to plant the next time you are in that field. If severe enough, you may need to consider seed treatments and other management tactics as well.

Are there conditions when growers should be on even higher alert as they scout for SDS? (i.e. during heavy rainfall, etc.).

If they have SCN, this increases their chances of having SDS and it being more severe. Heavy rains in June and July also really increase the chances of it being bad. 

What else should growers be aware of or what advice would you give them if SDS is present in their field?

You cannot manage this disease by rotating to corn – so focus on other management tactics when building your integrated management plan.


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