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Seed Treatment to control Bean Leaf Beetle and Bean Pod Mottle? 

            
     

      (Click on the thumbnail to view a bigger picture)

Due to recent interest in bean leaf beetles in South Dakota soybeans, I am letting you take an advanced
peek into my 2002 research on soybean seed treatments for potential use against bean leaf beetles and,
perhaps, bean pod mottle disease.

Once again, I am of the opinion that insecticidal sprays may not control bean pod mottle even
if you spray every single week for the bean leaf beetles.  How do I know this?  Our entomology
crew has two year's worth of data indicating that the yields of both "protected" or regularly sprayed
and "unprotected" or unsprayed soybeans were almost identical.

Furthermore, in 2000, both the sprayed and unsprayed soybeans showed signs of infection or mottling
in the seeds at harvest at 34% and 31% mottled seeds, respectively.  Yes, the sprayed beans had
more infected seeds and I cannot explain it.  Ask your friendly plant pathologist.  

This year, our soybeans were planted on May 23.  By the time the seedlings germinated, overwintered
bean leaf beetles were waiting for them.  Bean leaf beetles fed on the cotyledons, hypocotyl, and the
first true leaves.

Did the seed treatment (coated onto the soybean seeds before planting) protect the seedlings from
bean leaf beetle feeding?  The answer appears to be, "yes."

Last Friday (June 7), I took pictures of both seed treated and untreated versions of a soybean variety
and noticed a clear difference between the treatments.

Untreated seeds resulted in seedlings with leaves riddled with holes, and cotyledons scarred by bean
leaf beetles.  The treated seeds produced seedlings with few damaged leaves and cotyledons.

This is an important first step in trying to prove (or disprove) the hypothesis that protecting the soybeans
at emergence from feeding by bean leaf beetles could prevent bean pod mottle disease and associated
yield loss at harvest.

I will update you on the progress of this research through the growing season including the final yields
and infection rates.  I will reveal the actual treatments only at the conclusion of the research.

 Last Updated on Monday, June 10, 2002 by Mike Catangui

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