Soybean Rust: Spores Alone
Don't Make A Disease!

Over the past week, I have been approached by a number of growers and retailers commenting on how Asian soybean rust was found in Kentucky and Tennessee. The old saying "The Devil is in the Details" applies nicely here since what was "detected" were "soybean rust-like spores" and not infected (diseased) plants! Since very few of these "soybean rust-like spores" were collected in Kentucky (10 spores) and Tennessee (2 spores) a definitive determination through molecular analysis could not be done. Basically there wasn't enough DNA from these spores to test.

This is good news since it supports field observations indicating that the overall soybean rust spore levels in the southern US is extremely low. Things could change but it still would take time for the disease to develop in the southern US and release a sufficient number of spores that could pose a risk to Ontario soybeans. This however does not take into account other sources of spores such as the Caribbean, Mexico or other areas were soybean rust may be harbouring. These areas could pose a risk to Ontario if spores were to "piggy-back" onto a Hurricane or Tropical Storm.

Another factor that could impact us is the remnants of Hurricane Dennis which stalled over the Midwest. This has not only brought much needed rains to that area but could have made the environment more favourable for any transient soybean rust spores that land. For these reasons, scouting for soybean rust has intensified in Ontario and the US. For Soybean Rust Updates visit the OSG/OMAFRA soybean rust website or the USDA website.

Note - A Commerical Soybean Field In Alabama Found To Have Soybean Rust on July 12. This field is 1 mile from sentinel plot in which rust was detected on June 28. Rust continues to develop in the sentinel plot. As I get more information I will pass it along in future Crop Pest articles or visit the websites below.

Related Links

• Ontario Soybean Growers
  

• United States Department of Agriculture Soybean Rust Information Forecast Site

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