Consideration of peg strength and disease severity in the decision to harvest peanut in southeastern USA

The indeterminate nature and underground fruiting habit of peanut (Arachis hypogaea L.) makes it a challenge to determine the optimal harvest time. The objectives of this study were (1) to gain additional information about how maturity and canopy health influence peg strength, yield, and grade and (2) to address anecdotal claims of differences in peg strength and digging losses among cultivars. Field trials were established in Citra, FL, and Tifton, GA. Two peanut cultivars (Georgia-06G and Tifguard) were grown under two fungicide programs (full program: every 14-day spraying interval; and reduced program: every 28-day spraying interval), and harvested at three different maturity levels (early, optimum, and late based on an accumulated growing degree day method). The fungicide program had a significant impact on yield only in 2013 at Citra, likely because the canopy structure was decreased because of fungal disease known as leaf spots (causal agents: Cercospora arachidicola and Cercosporidium personatum). The timing of the harvest had a significant impact on yield, grade, peg strength, and digging loss. In addition, yield, grade, peg strength, and digging losses differed between the peanut cultivars. These results show that reduced fungicide program might affect the yield because of the disease severity and that the optimal harvest time should consider the level of the defoliation. Although there was no correlation between peg strength and digging loss, over-maturity can cause more digging losses compared to optimal harvest time. Tifguard had higher digging loss than Georiga-06G. This study provides additional useful information on cultivars to growers.