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Increased focus on pruning aids stinkbug management and quality

South African macadamia nuts' quality "exceptional" this year

Mayo Macs, which markets the macadamia nuts of its growers in Mpumalanga and KwaZulu-Natal through Netherlands-based Global Trading, reports “a brilliant season” regarding crack-out percentage. Usually the average is 35% but this season the amount of unusable nuts have decreased by about 1.5%, says Theunis Smit, Mayo Macs technical advisor for the Lowveld region. 

Dollar prices have risen on both macadamia kernels and nuts-in-shell according to Global Trading, which estimates that prices are 25% higher than last year but other industry experts reckon that the increase is more in the region of 10 to 15%, depending on quality. 

“South Africa is basically the balancing factor as their quality is seen as the top-quality product in China. The quality from South Africa this season is exceptional with very low insect damage,” the company reports on its website. 

Nico van Schalkwyk, marketing manager of Golden Macadamias says: “There are very poor quality NIS on the market this year on which the prices have dropped but buyers have a good idea of which companies deliver high quality NIS. There is a perception that South Africa and Australia deliver good product.”

The drought has adversely affected stinkbug populations in the macadamia producing regions prone to such damage, but the populations have also been kept down by more effective spraying programmes (plus more attention to sprayer calibration, although the jury is still out on high-volume versus low-volume spraying) facilitated by increased pruning within the South African macadamia industry.

Apart from climate and more focused spraying, the other factor that has played a role in their excellent crack-out percentage this season, has been an increased focus on pruning, says Theunis Smit, one of the authors of a guide on the subject compiled by the Mayo Macs technical team. Many South African macadamia farmers have either just pruned or are in the process of pruning at the moment, before the flowering season.

Pruning and the subsequent rejuvenation of trees is one of the top priorities for the macadamia industry, confirms Dr Schalk Schoeman of the Agricultural Research Council’s Tropical and Subtropical Crops division in Nelspruit. He believes that some growers are still wary of pruning their macadamia trees, partly because the advantage of pruning hasn’t yet been demonstrated to them, and partly because they have an emotional attachment to their beautiful large trees. Also, when a farmer starts pruning, it has to be repeated every subsequent season.

The South African industry might have awoken later to the necessity of pruning to keep tree height down and to improve light penetration and air flow, than their Australian counterparts, where macadamia trees have long been pruned mechanically, but this has had an unintended side-effect, the so-called “green wall of death”. This refers to an impenetrable wall of foliage created by a proliferation of side-shoots when apical branches are removed. Theunis Smit of Mayo Macs likens the effect to chopping off the heads of Medusa: where one is removed, four new ones grow, and so forth, exponentially.

Therefore in South Africa pruning is done by hand, removing strategic branches to achieve something close to a Christmas tree shape, which is a very time-consuming and labour-intensive process, only possible because labour costs in South Africa are much lower than in Australia.

Increasingly farmers are shaping macadamia trees from the get-go in new orchards, aiming for a triangular shape that allows better light penetration and more effective spraying against insect pests like stinkbug.

Another strategy, which has already been employed with success in Malawi, according to Dr Schoeman, is to take out every second row.

The problem comes in with mature trees, like in some older orchards. “It’s not that farmers are opposed to pruning but when you drastically prune a mature tree you reduce your yield for the next year or two, so it’s a big financial decision,” explains Alwyn du Preez, technical consultant in the macadamia industry. “It’s not an overnight thing. With big trees you have to do it bit by bit over a number of seasons, or growers just have to bite the bullet and do excessive pruning on smaller blocks to get them back to the correct size. In general the rule is that the optimal height of a tree is 80% of the row width.”

“The macadamia tree is an aggressive grower and to panelbeat those big trees into the desired Christmas tree shape… it’s not easy. Ideally one should start pruning a macadamia tree while it’s still in the nursery, to start its shaping,” says Dr Schoeman. 

Theunis Smit recommends a maximum height of 5m for macadamia trees in order to ensure effective stinkbug spraying, which has the added benefit of easier harvest. “Larger trees don’t give higher yield, that’s a misconception. Pruning is a relatively new thing in the subtropical fruit industry, not like in, say, the apple industry where trees have always been pruned. We’re advising our growers on how to find the balance and there are more growers who are pruning. The wood that’s taken out, is put through a chipper for a soil mulch, which is just as important.”

For more information:
Nico van Schalkwyk
Golden Macadamias
Tel: +27 13 733 5034

Dr Schalk Schoeman
Agricultural Research Council 
Tel: +27 13 753 7000

Theunis Smit
Mayo Macs
Tel: +27 84 919 5717

Alwyn du Preez
Independent technical consultant for the macadamia industry
Tel: +27 72 757 2218

Publication date: 7/17/2017
Author: Carolize Jansen
Copyright: www.freshplaza.com


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