The profitability of pecan [Carya illinoinensis (Wangenh.) K. Koch] orchard enterprises eventually decline if tree canopies encroach to cause excessive orchard shading. This deterioration of canopy light environment, and associated “sunlight stress”, typically increases alternate bearing intensity (I; Pearce and Dobersek-Urbanc, 1967), which is perhaps the economically most important biological problem faced by commercial pecan enterprises. Timely use of mechanized hedge-type pruning as a horticultural tool is potentially an effective approach for preventing orchard crowding and partial moderation of alternate bearing (Wood and Stahmann, 2004). It is increasingly adopted by commercial enterprises at high-light geographic locations; however, its usefulness at relatively low-light locations such as those of the southeastern United States merits assessment.
The relatively low-light environment of the southeastern United States exhibits considerable cloud cover and atmospheric water vapor (i.e., relative humidity) throughout the growing season. An important cultivar grown within this region is ‘Desirable’, a mild to moderate alternate bearer. Excessively crowded ‘Desirable’ orchards are increasingly common to the region as a result of a proliferation of plantings over the last two to three decades. Crowded light-stressed trees can trigger relatively severe alternate bearing, even in cultivars generally recognized as relatively low to moderate alternate bearers. Possible solutions to orchard crowding, and associated alternate bearing, include thinning orchards either by transplanting trees to establish new orchards (Wood et al., 1990) or by culling and removing trees. Both approaches are expensive. An alternative approach is mechanical hedge-type pruning.
Efficacy of mechanical pruning in relatively low-light environments was first tested during the 1970s by Worley (1985) in which it was concluded (based on drip-irrigated ‘Desirable’, ‘Elliott’, and ‘Farley’) that annual cuts to one of each of four sides (at 4.6 m) of the canopy, and topping (at 6 m), is unsuitable for commercial southeastern orchards. More recently, Lombardini (2006) found for east Texas, also a relatively low-light region, that one-time mechanical hedge-type pruning of nonirrigated Desirable, Cape Fear, and Kiowa cvs. reduced intercanopy crowding initially increased light within canopies and orchards but did not necessarily increase orchard productivity, nut yield, nut quality or reduce alternate bearing of nonirrigated trees. The present study evaluates the yield response of trees in a crowding ‘Desirable’ orchard, in a low-light environment, to three different short-cycle, moderate-width mechanical side-hedge pruning strategies. It is concluded that moderate-width mechanized side-hedge pruning of ‘Desirable’ does little to increase fruiting within the inner canopy and that short hedge-type cycles likely possess little commercial potential as a viable horticultural canopy management tool for ‘Desirable’ orchards located in relatively low-light environments.
Finn, G.A., Straszewski, A.E. & Peterson, V. 2007 A general stage key for describing trees and woody plants Ann. Appl. Biol. 151 127 131
Hudson, W., Brock, J., Culpepper, S., Mitchem, W. & Wells, L. 2007 Georgia pecan pest management guide Georgia Coop. Ext. Serv. Bulletin No. 841
Lombardini, L. 2006 One-time pruning of pecan trees induced limited and short-term benefits in canopy light penetration, yield, and nut quality HortScience 41 1469 1473
Worley, R.E. 1985 Effects of hedging and selective limb pruning of Elliott, Desirable, and Farley pecan trees under three irrigation regimes J. Amer. Soc. Hort. Sci. 110 12 16