Comparison of Elemental Sulfur Products as Tank Mix Partners with Azoxystrobin for Management of Late Leaf Spot (Nothopassalora personata) of Peanut

Management of fungicide resistance in Nothopassalora personata, the cause of late leaf spot of peanut (Arachis hypogaea), is a challenge in peanut production areas of the southeastern United States. Field experiments were conducted in Tifton, Georgia, in 2020 and 2021 and in Plains, Georgia, in 2021 to determine the effects of mixtures of seven elemental sulfur fungicide products with the quinone outside inhibitor (QoI) fungicide azoxystrobin on late leaf spot in fields where QoI-resistant populations of N. personata are suspected. Application of azoxystrobin or sulfur alone resulted in little reduction of the standardized area under the disease progress curve (SAUDPC) or final disease intensity ratings compared with the nontreated control. However, mixtures of azoxystrobin with all micronized sulfur products evaluated had SAUDPC values and final disease intensity ratings less than those in the azoxystrobin-alone or Microthiol Disperss 80W sulfur-alone treatments. One nonmicronized sulfur formulation had SAUDPC values and final intensity ratings similar to those of azoxystrobin or Microthiol Disperss 80W sulfur alone. The results suggest that multiple micronized elemental sulfur products have potential for use as mixing partners with azoxystrobin leaf spot control in fields where the efficacy of azoxystrobin alone is not adequate.