August 11, 2017   
  Issue 10  

Prepared by

Paul Kassel

Extension Field Agronomist



(712) 262-2264




Serving Clay, Buena Vista, Dickinson, Emmet, Hancock, Kossuth, Palo Alto, Pocahontas, Sac and Winnebago Counties



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Off target dicamba. Some of the   current issues involve:
-  soybean plants that are show symptoms of dicamba movement/cupped leaves on the top 5-8 nodes of the soybean plant.
-  Slow recovery - the newest leaves of affected soybean plants show dicamba effects 4-6 weeks after dicamba application in adjacent fields.
-  the main stem of the soybean plant has been stunted in severe cases.
Effects of dicamba drift.
-  yield effects from soybean exposure to drift amounts of dicamba to R1 or R2 stage soybean is usually negligible.
-  yield effects from dicamba drift amounts during the R3 or R4 stage may be negligible to as much as 9%.
-  What is unknown:
      • effects of multiple off target movement events
      • the effect of off target injury that started at late bloom stage/R2 and has continued into late pod/R4 stage.
What to do.
-  contact the retail and company representatives of the product that has moved off target - if movement originated from your field.
-  Contact the Pesticide Bureau of Iowa Department of Ag at (515)281-8591 to report a pesticide incident -if movement affected your field.
-  Consider some aerial imagery to assess the extent of the affected acres.
-  Contact insurance providers to discuss insurance coverage options.

Soybean growth stages, soybean aphid. The soybean crop will be susceptible to injury from soybean aphids for the following amounts of time. Many soybean fields are several days into the R4 stage.
Stage              description                                        days susceptible to aphids
R4                    ¾ in. pod at top 4 nodes                               24
R5                    1/8 in. seed in pod at top 4 nodes                 15
R6                    full size seed in pod at top 4 nodes              0
The economic threshold for treatment is 250 aphids per plant, more than 80% of the plants infested and aphid populations on the increase. Erin Hodgson explains the science behind this economic threshold in this ICM Blog article.


Prepared by Paul Kassel, Extension Field Agronomist

Phone: (712) 262-2264, Email: