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13
Jun
2017
Imposter of target spot popping up in some soybean fields
Author: Travis Faske, Extension Plant Pathologist

By Travis Faske, Extension Plant Pathologist

During the end of the 2016 cropping season target spot was seen in several soybean fields in the Mississippi River Delta including several counties in Arkansas.  Because of the widespread concern for target spot, consultants and growers are on the lookout for anything that looks like target spot.  Though the current weather conditions have been favorable for some foliar diseases like frogeye leaf spot, which is beginning to show up in some fields, it has not been favorable for target spot.  One of the most common imposters of target spot this season has been herbicide injury (Liberty) on Roundup Ready soybean varieties (Fig. 1).  This is a good reminder to confirm the disease or imposter identity before considering a course of action.  Some of the characteristic used to differentiate this imposter from a disease were…

    Figure 1.  Spots caused by herbicide (Liberty) injury on RR soybean.Figure 1.  Spots caused by herbicide (Liberty) injury on RR soybean.
  1. Spots do have yellow halo, but lack concentric rings that is common with target spot.
  2. None of the spots had any fungal structures.
  3. All spots were observed on leaves of a similar age of maturity (uniform layer in the canopy)
  4. Spots were found field wide
  5. Spots were found on nearby smaller soybean plants.

University trials are underway this season sponsored by the Arkansas Soybean Promotion Board to investigate the efficacy and usefulness of fungicides to protect soybean yield potential against target spot. If you have any questions, please contact Travis Faske (tfaske@ueax.edu)

 


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