Pecan Hedge-pruning: A Sustainable Management Option for the Southeastern US

Project Overview

LS20-340
Project Type: Research and Education
Funds awarded in 2020: $299,894.00
Projected End Date: 03/31/2023
Grant Recipients: University of Georgia; USDA-Agricultural Research Service
Region: Southern
State: Georgia
Principal Investigator:
Dr. Jason Schmidt
University of Georgia

Commodities

  • Nuts: pecans

Practices

  • Pest Management: integrated pest management, physical control

    Proposal abstract:

    Hedge-pruning of pecan (Carya illinoinensis) trees is a cultural management strategy that has been shown to mitigate effects of tree shading, reduce alternate bearing tendencies, improve tree health and increase orchard profitability. It has been practiced successfully in high-light environments and has become the standard method employed in the arid regions of the southwestern US. Environmental conditions in the southeastern US differ greatly from regions where hedging has been implemented (e.g., in terms of cloud cover and atmospheric water vapor). Thus, it is unclear whether hedge-pruning will be beneficial and sustainable in the Southeast, which is the major pecan-producing region in the US. Research is urgently needed to determine applicability and best management practices for hedge-pruning in the Southeast. Initial studies showed promise for hedge-pruning in the southeastern US. For example, in Georgia, winter hedge-pruned trees had reduced water stress compared to non-hedged trees, and nut weight and percent kernel were increased by hedge-pruning trees in the winter. Hedge-pruned trees also suffered less storm-related injury. Hedge-pruning has a positive impact on the management of scab, the most destructive disease of pecans in the southeastern US. Scab was easier to manage by bringing the nut crop within reach of efficacious spray coverage. Although preliminary studies of arthropod pest populations in hedged-pruned and non-hedged trees showed little difference between treatments implying that hedge-pruning does not increase pest pressure, there were indications that hedge-pruned trees had reduced injury from black pecan aphids, Melanocallis caryaefoliae, a major insect pest in pecans, and had increased aphid parasitism early in the season.

                In recent years in the Southeast, hedge-pruning pecan has gained popularity among growers. Therefore, research is warranted to determine the ecological and economic sustainability of hedge-pruning in the southeastern region. In fact, pecan hedge-pruning is listed as a major research priority identified by the Georgia Pecan Growers Association. There are unknown ramifications of hedge-pruning that must be addressed. Specifically, the impact of hedge-pruning younger trees versus older trees is unknown, and the effect of timing of hedge-pruning (summer versus winter) on the tree, and impact on critical pests and diseases is preliminary. In relation to these aspects, we propose assessing critical horticultural parameters (nut yield, quality, water-use efficiency, and nutrition), disease (incidence and severity of scab, colonization of branches by wood rot fungi), insect pest and natural enemy populations and pest-related injuries. Moreover, hedge-pruning trees may result in changes in the quantity of radiant penetration to the understory, impact soil moisture and affect the biotic community. Thus, we will evaluate impacts of hedge-pruning on soil-borne entomopathogens that provide biocontrol services against soil inhabiting pecan pests including pecan weevil, Curculio caryae. There will be a comprehensive economic analysis and implementation of Extension and Outreach programs based on the research results. Findings from these studies will be beneficial to other orchard and tree nut production systems where hedged-pruning is practiced.

    Project objectives from proposal:

    Our main goal is to evaluate the sustainability of hedge-pruning pecan trees in the southeastern US. Prior research demonstrated that hedge-pruning can have positive impacts on some horticultural parameters, and can improve disease and insect management. However, the relative benefits of hedge-pruning trees of different ages, or hedge-pruning trees at certain times of the year is not known. We propose the following objectives:

    1) Determine relative impacts of hedge-pruning young and older trees by comparing horticultural and production variables, disease and insect pest prevalence, and natural enemy populations in hedged-pruned and nonhedged young and older pecan trees.

    2) Define the effects of timing (summer versus winter) of hedge-pruning of pecans on the variables listed in objective 1.

    3) Perform an economic feasibility assessment of hedge-pruning pecan based on the results obtained from objectives 1 and 2.

    4) Share the results with growers and other stakeholders via diverse Extension and outreach programs.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.