Foliar Fungicide Impact on Cotton in 2024
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Collapse ▲Commercially available foliar fungicides (Table 1) were evaluated for the management of two emerging cotton diseases, target spot and areolate mildew. These diseases result in foliar leaf spots, powdery growth, and early defoliation. This trial was conducted in a research plot at the Upper Coast Plains Research Station located in Rocky Mount, NC. Foliar disease pressure was high in the area due to early-season drought conditions followed by hurricanes and heavy rains.
After the last treatments were applied, defoliation was assessed weekly, and foliar disease symptoms (lesions and white powdery growth) were assessed biweekly. The combined AUDPC from disease incidence and severity was calculated into a severity scale (1-10), with 1 being the lowest severity and 10 being the highest. The two center rows of each plot were harvested, and the adjusted yield (lbs of lint) was calculated from the plot yield (lb) and ratio of seed weight (lb) and lint weight (lb).
Fungicides reduced the impact of target spot and areolate mildew in cotton by reducing defoliation. Less defoliation was significantly correlated to higher yields (-0.067 and p-value <0.05). There were notable increases in yield with some of the tested fungicides (Table 2). However, the overall differences in disease, defoliation, and yield among the fungicide treatments were not statistically significant.
| Table 1. Fungicide Products, Active Ingredients, Fungicide Resistance Action Committee (FRAC) Code, Rate, and Application Timing | ||||
| Fungicide | Active Ingredients | FRAC | Rate (fl oz/A) | Application timing |
| Untreated | – | – | – | – |
| Revytek | Mefentrifluconazole, Fluxapyroxad, & Pyraclostrobin | 3, 7, &11 | 12 | 3rd week of bloom |
| Revylok | Mefentrifluconazole & Fluxapyroxad | 3 & 7 | 5.5 | 3rd week of bloom |
| Priaxor | Fluxapyroxad, & Pyraclostrobin | 7 & 11 | 6 | 3rd week of bloom |
| Miravis Top | Pydiflumetofen, Difenoconazole | 3 & 7 | 13.6 | 3rd week of bloom |
| Topguard EQ | Flutriafol & Azoxystrobin | 3 | 14 | 3rd week of bloom |
| Quadris Flowable | Azoxystrobin | 11 | 8 | 3rd week of bloom |
| Xyway | Flutriafol | 3 | 15.2 | At Planting |
–
| Table 2. Disease severity, Defoliation, and Yield for Cotton Fungicide Applications | ||||||
| Fungicide | Target spot severity scalea | Aerolate mildew severity scalea |
Defoliation severity scaleb | Yieldc (lint lb/acre) | Yield Difference (%) | Fungicide & Application Costsf ($) |
| Untreated | 10 | 10 | 9.2 | 1476.95 | ||
| Revytek | 6.8 | 2.4 | 1.4 | 1615.71 | +9.0 | 45 |
| Revylok | 6.7 | 4.9 | 4.7 | 1476.10 | -0.1 | 31.5 |
| Priaxor | 3.4 | 2.2 | 1 | 1670.89 | +12.3 | 28 |
| Miravis Top | 2.4 | 1.3 | 6.9 | 1418.50 | -4.0 | 26.32 |
| Topguard EQ | 3.8 | 2.3 | 5.6 | 1513.14 | +2.4 | 25.56 |
| Quadris Flowable | 4 | 2.6 | 8.2 | 1511.77 | +2.3 | 20.94 |
| Xyway | 1.3 | 3.9 | 10 | 1334.23 | -10.2 | 35 |
a Disease severity scales are standardized in at 1-10 scale from the combined AUDPC from biweekly incidence and severity assessments
b Defoliation severity scales are standardized in at 1-10 scale from the AUDPC from weekly severity assessments
c Yield (lbs of lint/acre) was calculated from the plot yield (lb) and ratio of seed weight (lb) and lint weight (lb)
d This reflected the estimated sum of the fungicide prices and application costs in North Carolina