Impacts of hedging and thinning on arthropod pest populations in the upper and lower canopies of 25-year-old pecan trees

Pecans are one of the top 10 commodities in Georgia, bringing in $263M in Farm Gate Value in 2019. One practice used by growers to control the size of pecan trees is hedging, which prunes the sides and the tops of the trees. Previous studies have looked at the horticultural and disease parameters impacted by hedging, but not much is known on how hedging impacts insect populations. Leaf feeding pests were monitored over two years in 25-year-old ‘Desirable’ pecan trees. In 2020, hedging versus no hedging was observed, and in 2021, the non-hedged sections of the orchard were thinned, and hedging was compared to thinning of the orchard. Leaves were collected in June, July, and August from the upper and lower canopies to monitor for leaf feeding pests and related damage including aphids, mites, leaf miners, and phylloxera. In 2020, for aphid populations, the hedged trees had more aphids, in July, the lower canopy had more aphids, and in August, there was an interaction between the treatment and canopy location. Pecan leaf scorch mites had higher populations in the lower canopy. Phylloxera galls only had a significant difference in one month, with non-hedged trees having a greater number. Results for the 2021 season are pending.