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EVALUATING FUNGICIDE EFFICACY ON AREOLATE MILDEW IN GEORGIA

Applied Research

Jeremy Kichler
County Extension Coordinator
University of Georgia
Moultrie

Abstract

There is an increasing presence of areolate mildew (Ramularia gossipii and Ramulariopsis pseudoglycines) in Georgia cotton. Areolate mildew cost Georgia cotton growers an estimated $10 million in economic losses in 2021. In 2023, there was increasing concern from growers, consultants, and retailers about the efficacy of azoxystrobin on areolate mildew. In response to this issue, two field trials were conducted in Colquitt County, Georgia during the 2024 and 2025 production season to evaluate the efficacy of fungicides in the management of areolate mildew.

In 2023 and 2024, two on-farm fungicide trials were conducted in Colquitt County. The varieties planted in 2023 and 2024 were Dynagro 3799 and DPL 2333, respectively. The plots were 18 rows wide and averaged 1200 feet long. Foliar fungicide treatments included azoxystrobin (Abound, 6 fl oz/A), azoxystrobin (Abound, 6 fl oz/A) + sulfur (Drexel Suffa, 58 fl oz/A), pyraclostrobin + fluxapyroxad + mefentrifluconazole (Revytek, 10 fl oz/A) and difenoconazole + pydiflumetofen (Miravis  Top, 13.7 fl oz/A). Revetek was applied in 2023 and the sulfur tankmix applied in 2024. Fungicide treatments were applied with an 18-row sprayer during the 3rd week of bloom.  Yield data was taken at harvest both years.

In 2023, at 52 DAT, the Miravis Top (45%) and Revytek (38%) significantly reduced canopy defoliation compared to the untreated check (80%) and Abound (83%). No significant differences in lint yield were noted at harvest between the Miravis Top, Revytek and untreated check, with yields ranging from 1483 lb to 1523 lb.  However, the Miravus Top (1518 lb) and Revytek (1523 lb) significantly increased yields over the Abound (1385 lb). 

In 2024, canopy defoliation was rated at 33 and 44 days after treatment (DAT). Suffa tank mix with azoxystrobin did decrease defoliation compared to azoxystrobin alone. There was no significate difference in yield but 80-100 lbs with the Suffa tank mix with azoxystrobin. This could explain why there was a decrease in defoliation and an increase in yield with Suffa.  Isolates of the R. pseudoglycines from the on-farm site in Colquitt County did have the gene mutation for QoI resistance.

 

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.

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Authors: Tanner Wilson, Jeremy Kichler, Robert Kemerait
  1. Wilson, T. Colquitt County ANR Educator , University of Georgia Cooperative Extension , Georgia, 31788
  2. Kichler, J. Colquitt County Extension Coordinator, University of Georgia Cooperative Extension , Georgia, 31768
  3. Kemerait, R. Extension Plant Pathologist, University of Georgia Cooperative Extension , Georgia, 31793