Evaluating the Impact of Canopy Defoliation Levels at Two Critical Timings in Peanut.

Information is lacking regarding pest management strategies to properly manage canopy defoliation in peanut. Canopy defoliation can reduce photosynthetic capacity, and in turn, pod yield. Peanuts are susceptible to defoliation from both foliage-feeding insects and foliar diseases which can affect the crop throughout the growing season. Preliminary research conducted in Mississippi indicated that peanuts were especially sensitive to defoliation at two critical timings, 40 and 80 days after emergence (DAE). At these two critical timings, yields were significantly and consistently reduced when the canopy was completely defoliated. Knowing how current peanut cultivars respond to defoliation at various levels will help extension personnel make informed pest management decisions and will allow growers to become more efficient users of pesticides. The objective of this research was to determine what percentage of canopy defoliation causes a significant yield reduction at these two critical developmental stages. Trials were conducted at the Delta Research and Extension Center in Stoneville, MS as well as the R. R. Foil Research Farm in Starkville, MS in 2015 and 2016. Treatments included 0, 20, 40, 60, 80, and 100% defoliation at 40 and 80 DAE, along with a non-defoliated control. In 2016, a 10% defoliation level treatment was included for both timings because significant yield loss occurred at 20% defoliation, 80 DAE in 2015. Both locations followed similar trends, with no significant yield reductions being observed at the 40 DAE defoliation event. Defoliation at 80 DAE provided significant pod yield reductions. In 2015, yield was reduced by 25% at a 20% defoliation level, with significant yield loss occurring at each higher level. In 2016, 40% defoliation at 80 DAE resulted in a 12% yield loss, with a loss as high as 27% observed at 100% defoliation. Ultimately, this data will be used to develop defoliation thresholds in peanut.