Impact of 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 disease 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 both 2015. Treatments included 0, 20, 40, 60, 80, and 100% defoliation at 40 and 80 days after emergence, along with a non-defoliated control. Both locations followed similar trends, with few significant yield reductions being observed at the 40 DAE defoliation event. The 80 DAE defoliation event provided significant pod yield reductions ranging from 25% to 40% when compared to the non-defoliated control. Ultimately, this research will be used to develop defoliation thresholds for insects in peanut.