POTENTIAL OF MICRONIZED SULFUR FOR MANAGEMENT OF AREOLATE MILDEW IN GEORIGA
Applied Research
Jeremy Kichler
County Extension Coordinator
University of Georgia
Moultrie
Abstract
Areolate mildew has become an increasingly important foliar disease of cotton across Georgia, replacing target spot (Corynespora cassiicola) as a primary late season disease of concern. In 2021, areolate mildew caused an estimated $10 million in economic losses to Georgia cotton producers. By 2023, growers, consultants, and retailers reported reduced efficacy of azoxystrobin for management of this disease, raising concerns about the development of resistance to QoI (strobilurin) fungicides. In response, field trials were conducted during the 2024 and 2025 growing seasons to evaluate whether tank mixing micronized sulfur with azoxystrobin could improve control of areolate mildew. Previous Georgia research showed that micronized sulfur enhanced QoI fungicide performance against leaf spot diseases of peanut in areas where fungicide resistance was present. In 2024, a field trial was conducted in Colquitt County using Delta Pine 2333 B3XF, where areolate mildew was the predominant disease. Treatments included azoxystrobin (Abound, 6 fl oz/A), azoxystrobin + sulfur (Abound, 6 fl oz/A + Drexel Suffa, 58 fl oz/A), and difenoconazole + pydiflumetofen (Miravis Top, 13.7 fl oz/A). Fungicides were applied during the third week of bloom. Early ratings showed no significant treatment differences. However, at 46 days after treatment, Miravis Top significantly reduced canopy defoliation compared to azoxystrobin alone, while azoxystrobin + sulfur numerically reduced defoliation compared to azoxystrobin alone. Yield differences were not statistically significant, but the azoxystrobin + sulfur and Miravis Top treatments numerically increased lint yield by 80 to 100 lb/A compared to the untreated check. In 2025, a similar trial was conducted in Colquitt County with Delta Pine 2028 B3XF. No significant differences among treatments were observed for canopy defoliation, areolate mildew incidence, or yield. Prolonged dry conditions following bloom likely limited disease development. Overall, results indicate that azoxystrobin performance against areolate mildew has declined since 2023 in some locations. In 2024, addition of sulfur improved late season disease suppression where reduced sensitivity to azoxystrobin was evident, while no benefit was observed where resistance was not detected. Based on these findings, growers should not apply QoI/strobilurin fungicides alone for areolate mildew management unless local populations are confirmed to remain sensitive.
Poster has NOT been presented at any previous NACAA AM/PIC
This poster is being submitted only for display at AM/PIC. Poster is not to be judged, but the abstract will be published in the proceedings.
Click to view Poster
Authors: Jeremy Kichler, Tanner Wilson, Robert Kemerait
-
Kichler, J. County Extension Coordinator, University of Georgia Cooperative Extension , Georgia, 31788
-
Wilson, T. Colquitt County Extension ANR Educator, University of Georgia Cooperative Extension , Georgia, 31788
-
Kemerait, R. Extension Plant Pathologist, University of Georgia Cooperative Extension , Georgia, 31793