Managing Global Resources for a Secure Future

Information is lacking regarding 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 foliage-feeding insects which can potentially reduce yield throughout the growing season. Preliminary research indicated that peanuts were especially sensitive to defoliation at two critical timings, 40 and 80 days after emergence (DAE). At these two critical timings, yield was significantly and consistently reduced when the canopy was completely defoliated. The objective of this research was to determine the percentage of canopy defoliation that causes a significant yield reduction at these two critical developmental stages. Trials were conducted at two locations in Mississippi in 2015 and 2016. Treatments included 20, 40, 60, 80, and 100% defoliation at either 40 or 80 DAE, with a non-defoliated control. Yield, grade, canopy heights and widths, and plant biomass were all evaluated. Regression analysis found no significant reduction in pod yield at the 40 DAE defoliation timing at any level of defoliation. Similar analysis at 80 DAE showed pod yield reductions of 18.6 kg/ha for each 1% increase in defoliation. At 80 DAE, yields may be reduced upwards of 186 kg/ha following 10% defoliation. When considering average crop value and insect control costs, analyses indicated that the economic injury level is 5% defoliation at 80 DAE. This data will be used as a basis for developing action thresholds in peanut production in Mississippi as well as the Southeast U.S. 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.