The cool spring and lack of hot weather pre-Christmas has delayed the maturity of most horticultural crops, almonds included. It has posed a serious challenge for the ABA’s high health status budwood program in meeting the pre-Christmas demand from nurseries for buds.
The swap from producing trees over an 18-month period for sale to producing trees in 6-7 months has increased in recent years, however this practice puts pressure on the delivery of budwood of sufficient maturity early in the budwood season. It also compacts the grafting season for nurseries wanting to get as many trees as they can in the ground for as long as they can to maximise the growth period.
This year, the weather has meant that bud maturity has led to the program being three to five weeks behind normal. The ABA operates two motherplanting sites as a risk management strategy and to meet demand in period of heightened nursery tree production.
The sites at Monash in SA and Colbinabbin in Victoria produced over two million buds in 2015/16. The logic behind the risk management strategy was recently proven with the recent hail storm in the Riverland causing some budwood damage at the Monash site, whilst the motherplanting at Colbinabbin has suffered hail damage in the past.
The other major risk that having multiple sites mitigates is virus contamination. The core reasons for having industry motherplantings is to ensure buds are as close as possible to the original high performing trees and the management practices undertaken on-site to prevent the incursion of debilitating viruses that stifle potential tree development and future yields.
With the recent identification in Australia of two new viruses impacting Prunus trees, the need to source high health status budwood, where the trees are tested for viruses, is again highlighted. The new pathogens being Apricot Vein Clearing Associated Virus (AVCaV) and American Plum Line Pattern Virus (APLPV) which has symptoms like those for Prunus Necrotic Ringspot Virus (PNRV) and Apple Mosaic Virus (AMV).
With the release of the new University of Adelaide varieties the ABA is planning to establish a further motherplanting site at the Loxton Research Centre, and is receiving support in this from the South Australian Government through PIRSA and SARDI. The 0.8 hectare site will increase available buds from the five PBR’d varieties and other selections that are outperforming Nonpareil yields in trials and have favorable characteristics, including being self-compatible and with complete shell seals which reduces insect damage.
Along with the delayed maturity of budwood the nurseries are also needing to manage the delayed and slow growth of rootstocks.
Just before Christmas, the Colbinabbin site will be operating well below its production capacity with the mother trees yielding at less than a third the rate normally expected leading to the program there being at least a month behind the expected schedule (based the 2015/16 cutting season). The Monash site is faring better than Colbinabbin, producing approximately 10,000 buds per day during December, which is well below its optimum capacity. With the expected warmer days at Christmas, the capacity at Monash should increase to 15-20,000 buds per day. Both the Monash and Colbinabbin sites will be cutting during the Christmas and New Year period with enough cutters and de-leafers to achieve a capacity of 20,000 buds per day from each site. Regular updates on progress are being sent to nurseries as the push to increase bud yields is managed.
With the unseasonal weather being experienced currently there is a chance of an extended summer and associated growing period for the trees in the nurseries which may increase the size of trees come winter.
One of the industry’s producers with substantial orchard expansion occurring recently noted that the move to relying on one year old trees was a risk strategy as many things can impact on getting trees to a sufficient size. When plans are being made, two year old trees should be part of the thinking.