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Row Crop Disease Update

 

  1. We still have not found Asian soybean rust to date in Georgia, nor has it been found in Alabama.  Last week it was identified in Mississippi for the first time this season and it has now been found in two counties in Florida near the Georgia border.  Conditions have been quite favorable for spread in recent days, so growers should be aware of this in the extreme SW corner of our state.

 

  1.  Target spot of cotton has been slow to develop this season, though it has been present in a growing number of fields.  Once the crop get beyond the 6th week of bloom, I am not too much concerned with the disease any more, at least for now.

 

  1.  Bacterial blight/Angular leaf spot has been much more common than I remember in the past and has been most commonly reported in DPL 1454, though it has also been found in lesser amounts in other varieties as well.  Unfortunately, there is nothing that can be done to manage this disease (i.e. nothing to spray); however, even at its worst, yield losses rarely are reported to exceed 10% and are often less.  The disease manifests itself as defoliation and, frequently, boll rots where you first see water-soaked lesions on the bolls.

 

  1.  White mold of peanut has become increasingly problematic.  No big surprise as conditions are absolutely perfect for it now (hot, humid and wet).

 

What to do to increase control of white mold if you are not satisfied with results?

 

  1.  REMEMBER:  In a season like this, the perfect storm of a season, even our BEST fungicide programs for white mold may only provide ~70% control.  No program will stop all initial “hits” of white mold where a plant here, there and across the field wilts.  BUT a fungicide program MUST prevent the disease from spreading from that plant to other plants within the row and down the row.

 

  1.  Spraying the peanut field at night or in the darkness of early morning when the leaves are folded is a GREAT way to get the fungicide where it needs to be (the crown of the plant).

 

  1.  Tebuconazole/Bravo is good but not the best for white mold.  If problems are developing, you may shift to a more effective (an more expensive) program.

 

  1.  Consider extending the white mold schedule.  Even if you have completed a “traditional” white mold program, you may extend the program, perhaps using the Tebuconazole/Bravo program if you have been on a more effective/expensive program.  But please consider resistance management when choosing a fungicide to extend with.

 

  1.  Use anticipated rain events and irrigation to move the fungicide to the limbs and to the crown of the plant.

 

By Dr. Bob Kemerait