Research Spotlight | Managing Target Spot in Cotton and Soybeans

Results from a three-year study of fungicide applications for target spot in cotton show a greater yield response from later applications than early.

Scientists with the University of Tennessee Institute of Agriculture evaluated different timings for fungicide applications in disease-infested cotton research plots located at the West Tennessee AgResearch and Education Center. Their evaluations showed that cotton treated with a single application of fungicide during the fifth week of blooming averaged yields just shy of 1,900 pounds of lint per acre. This was a significantly higher yield average than cotton treated during the first or third week of bloom, which yielded 1,811 and 1,830 pounds, respectively.

The same was true for double fungicide applications, with cotton treated during the third and fifth weeks of bloom averaging approximately 1,960 pounds per acre compared to just 1,838 pounds per acre for cotton treated with fungicide during the first and third weeks of bloom. The average lint yield for the non-treated check was just over 1,800 pounds.

Target spot is a relatively new threat to Mid-South cotton production. Caused by the fungus Corynespora cassiicola, target spot can lead to early defoliation and potential yield loss in infected fields. Researchers with UTIA have noted that both the occurrences and severity of the disease have increased each year since 2013 when it was first discovered in Tennessee.

“While target spot has not yet been a major issue in most Mid-South fields, within the right environmental conditions it can cause rapid premature defoliation,” says Heather Kelly. “The fact that it continues to occur earlier and more often in our area is raising concerns for producers. Now that we’ve had several years to evaluate this disease, we see that the later applications of fungicide are more effective in reducing disease and defoliation in target spot-infested cotton.”

Kelly presented her study findings at the 2017 Beltwide Cotton Conference in Dallas. The title of her presentation was “The Response of Cotton to Fungicide Applications for Target Spot in Tennessee.” She also covered this topic at the Cotton Tour, held at the West Tennessee AgResearch and Education Center on Wednesday, September 6.

The study also found that while double fungicide applications yielded the most lint (1,899 lbs) across years and varieties, there was not a statistically significant difference in lint yield when only one fungicide application was made (1,847 lbs). The non-treated check averaged a lint yield of 1,810 pounds.