Cotton Cropping Frequency and Variety Selection Impact on Target Spot, Cotton Root Knot, and Yield

Impact of cotton cropping frequency, variety on target spot severity, and cotton root knot nematode (Meloidogyne incognita Race 3) was evaluated in an ongoing rotation study at the Wiregrass Research and Extension Center in Headland, AL. In 2014, cropping frequency treatments included 1) continuous cotton (28 years); 2) two consecutive years of cotton following one year of peanut; 3) one year out with cotton following peanut; and 4) two year out rotation with cotton following two years of peanut. Cotton varieties included Phytogen 499, Phytogen 427, Deltapine 1050, and Deltapine 1454NR. A factorial arranged in split plot with cotton cropping frequency as the main plot and cotton variety as the split plot treatment was used. Target spot ratings were recorded on 1 August, 20 August, 2 September, 15 September, and 25 September. Areas under disease progress curve (AUDPC) values were calculated from the leaf spot data recorded over the study period. Cotton cropping frequency and variety impacted target spot intensity at the latter three rating dates and AUDPC values. A significant cropping frequency x variety interaction noted at the 2 September and 25 September rating dates showed that the impact of cropping frequency on target spot differed by variety. At the final rating date, defoliation levels for Phytogen 427 but not the other varieties were affected by cropping frequency. While Phytogen 499 suffered the heaviest defoliation, the least damage was noted on Deltapine 1454NR. Season-long, similar defoliation levels were recorded for the continuous cotton and two years of cotton following one year of peanut. The one and two year out cropping patterns had similarly lower AUDPC values compared with the latter cropping pattern. Final root knot nematode and yield data will be presented.