MECHANIZED MANAGEMENT OF PRUNING RESIDUES IN SWEET CHESTNUT ORCHARDS

Abstract

In Italy, Dryocosmus kuriphilus is a major insect pest of chestnut orchards causinggall formation and significant yield losses. The use of the parasitoid wasp Torymussinensis is an effective biological control method that requires the appropriatemanagement of the pruning residues, to preserve the woody galls in which T.sinensis adults overwinter. An innovative tractor-pulled combined mechanicalshredder was tested for treating the residues, once the pruning operations arecompleted. The machine processes the residues in a single-step, picking-up theprunings from the orchard floor, shredding them to appropriate size, and collectingthem into a rear container. The shredded residues may then be concentrated into afew piles for the long-term field storage, until next spring. The aim of the studywas to evaluate the machinery’s operative performance, the quality of the shreddedbiomass and the impact on gall integrity. In the field trials, the machineryeffectively shredded the residues achieving an average operative capacity of 1.19ha∙h-1 and a work capacity of 1.79 t∙h-1. Moisture content, apparent bulk density,and particle size distribution of the shredded biomass were determined. Over 95%of wood chips were included in the 3.15-45 mm size range, making them suitablefor use in residential biomass furnaces. The calorific power of the chestnut residueswas similar to that reported for other hardwood species (18-20 MJ∙kg-1). Also, themechanical action of the shredder preserved at least two thirds of the winter galls,safeguarding the parasitoid’s life cycle.