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‚ÄčTarget spot is a common and sometimes damaging disease of cotton.  In field trials at the Gulf Coast Research and Extension Center (GCREC), yield losses up to 400 pounds of lint per acre of have recorded on the target spot susceptible variety Phytogen 499 WRF.  The majority of other commercial cotton varieties from Deltapine, Phytogen, and Stoneville/Fibermax have partial disease resistance, thereby making them less prone to significant yield loss than Phytogen 499 WRF as well as fail to respond to fungicide inputs.  Other varieties that have suffered significant but smaller target spot-incited yield losses when compared with Phytogen 499 WRF include Deltapine 1252 B2RF and Fibermax 1944 GLB2.  Factors increasing the risk of damaging target spot outbreaks include excessive nitrogen fertilization and irrigation coupled with frequent July and August showers, while dry and hot weather during this same period will slow and in some cases prevent disease development. Target spot damage is much more likely in cotton grown across the southern third of Alabama and adjacent counties in the Florida Panhandle.  While significant defoliation is sometimes seen in Central AL cotton, yield losses have not been as consistent nor as high as those observed further south, particularly in SW AL.  To date, target spot defoliation in North AL irrigated cotton has been minimal and yield impacts negligible. Fungicides, which delay target spot-incited defoliation, can reduce disease-related yield loss.  The best yield protection with fungicides has been seen in Coastal and South AL in intensively managed cotton.  High risk fields in Central AL but not North AL occasionally benefited from protective fungicide treatments.  Given the relatively slim profit margin for cotton, fungicides are a costly input that should only be considered in high-yield (2.5+ bale/A) potential cotton in high risk settings.  Sizable yield gains from fungicide inputs are unlikely in cotton, particularly outside of SW AL, with a yield potential below 2 bales/A.  The most consistent yield gains have been obtained with Priaxor followed by Headline, Quadris, Twinline, Elatus, and Topguard.  Application rate does not greatly impact the efficacy of any of the above fungicides.

2017 Target Spot Fungicide Options TI REV.pdf


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