Refining a Solar Radiation Stress Index for Cotton in the Mid-South

In Mid-South cotton fields, a marked increase in small boll abscission following a progression of cloudy days may be erroneously attributed to effects of arthropod pests. Photosynthesis is negatively affected during overcast, cloudy days.  Cotton plant sensitivity to light intensity is highest when photosynthetic demand is highest -- during the plant reproductive development period.  With inadequate photosynthetically active radiation, plants will shed young bolls that are less than two weeks old. Overcast conditions during the pre-flower growth stage, when photosynthetic demand is not as high, does not result in square shed, but those same conditions during flowering and boll filling stages will result in fruit loss. A field measurement of weekly cloudiness was generated for the production seasons in 2012-2016 at Judd Hill Research Station in northeast Arkansas.  This measure was related to weekly measures of boll shed in the research plots at the station.  This research will facilitate the determination of plant response and help improve our understanding of yield variability in the cloudy, Mid-South production region.