Begin
Scouting For Soybean Cyst Nematode
| Author: |
Albert Tenuta -
Field Crop Plant Pathologist/OMAFRA Ridgetown
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| Creation Date: |
28 June 2007
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| Last Reviewed: |
28 June 2007
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It is that time of year again for me to talk about soybean cyst nematode.
While driving to Purdue University in West Lafayette, Indiana early
last week, Terry Anderson (AAFC- Harrow) and I noticed a large number
of fields that were displaying typical SCN symptoms.
Our comment at the time was that it would not be long for those same
symptoms to show up in Ontario and it wasn't. SCN symptoms are showing
up in the traditional areas of southwest Ontario plus in newer areas
such as the Princeton area (thanks to Leanne Freitag, Cargill). Symptoms
have accelerated this week primarily due to the dry conditions and
the early spring we experienced.
The spring allowed the nematode to begin development early and the
dry conditions have been good for SCN reproduction. The return to
more seasonal temperatures will help the nematode.
Growers need to scout their fields and dig-up plants. Pay particular
attention to fields where the plants are stunted and/or the stands
tend to have an uneven or wavy appearance. Affected areas are commonly
oval or elliptical that increase in size annually and often elongate
according to the direction of tillage or soil texture patterns of
the field. The leaf margins of infected plants are yellow and may
resemble nitrogen, manganese or potassium deficiencies. The root systems
of infected plants are usually poorly developed and discoloured due
to secondary invaders (root rot organisms).
In addition, the roots have a reduced number of functional nitrogen
fixing nodules. Symptoms are more pronounced when soybeans are under
stress from dry conditions, soil compaction or low soil fertility.
Symptoms often show up in stressed areas of the field or entry ways
/ field boundaries (infested soil). Keep in mind though that the most
common SCN symptom - IS NO SYMPTOMS!

Figure 1. SCN Cyst on
Soybean Roots
The lack of symptoms is particularly true when the crop is growing
vigorously. The above ground symptoms I described earlier often disappear
under good growing conditions so don't be surprised if this occurs
when we get a good rain. The fact that SCN damage can go under the
radar is one reason why many growers are unaware they have a SCN problem
until yields are affected significantly.
Therefore be proactive! Get out and enjoy the cooler temperatures
and don't forget to dig up those soybean plants. Examine them for
the small white to yellow cysts (pin-head size). This is still the
best method to detect SCN.
For more information:
Toll Free: 1-877-424-1300
Local: (519) 826-4047
E-mail: ag.info.omafra@ontario.ca
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