Disselfontein

Size does matter
The Hortgro field-day orchard at Disselfontein is Celina on BP1, established in 2016 at 4.0 x 1.5 metres. Celina is an early blushed pear. It’s typically marketed before Rosemarie in weeks 1–4. In 2024 Disselfontein started harvesting their Celinas on 2 January. “Size is the most important thing with Celina,” commented Karolus. “But based on our previous seasons, you have less than 90 days from full bloom to harvest. You don’t have much time to develop fruit size.” “This past season was probably our shortest ever – 88 days from full bloom to harvest,” added orchard manager Romario Cuttings. The orchard yielded 60 tonnes per hectare with pack-outs of 89% Class 1A, and the orchard cull was 18%. In 2022 yields were 54 tonnes per hectare with a 92% Class 1A pack-out and a 20% orchard cull. “The goal here is 55 tonnes per hectare,” said Mico Stander, soil scientist at AgriMotion and the nutrition and irrigation adviser at Disselfontein. Keeping crop load relatively low helps boost fruit size. In 2023 the yield was 81 tonnes per hectare with a 9.2% Class 1A pack-out. “The orchard was hit by hail, so the fruit was left on to maximise on juice,” said Stander. “This was before nets were put up.” Disselfontein erected nets over the Celinas in November 2023. “We had hardly closed the nets when we opened them again because we’d finished harvesting,” joked Karolus. “So, we don’t yet have much to say about pears under nets – we’ll start building up a history from this season.”

Pears under netsThe Celinas are under retractable grey 14% shade nets. The trees are uncovered from after harvest until the pollination hives are removed. Disselfontein generally gets hail in November and December, but Karolus doesn’t take any chances – he prioritises covering the trees as soon as the bees have finished working. “You can’t hang around because you don’t have labour,” he said. Karolus has yet to experience problems with red colour development under the nets and strives to produce fruit with both red colour and good size. As volumes of Celina rise, markets could demand increased red colour. Red colour development in pears differs from that in apples. In pears, red colour peaks about halfway between bloom and harvest. It tends to fade in the second half of this period due to less formation of new pigment, natural degradation of existing pigment, pigment dilution as pears grow, and increased pigment breakdown under warm conditions. Pears require light for red pigment synthesis, but light also degrades the pigments. As the pear’s ability to make pigment drops later in the season, breakdown tends to exceed synthesis. These opposing processes make it hard to predict the effect of nets. However, nets are likely to reduce red colour development earlier in the season while possibly helping to preserve red colour later in the season, especially if temperatures under the nets are lower. The benefits of black nets on Packham’s Triumph were discussed during the field day. According to Christo Strydom, Wolfpack General Manager, one Langkloof grower has black draped nets over Packham’s Triumph from three-quarters petal drop until harvest. The black nets have been far more effective than grey nets in preventing sunburn. “If we look at sunburn in Packham’s, there’s no two ways about it – you must have nets,” he said. “The core of the problem is the change in quality standards, which is why our pack-outs per hectare are low. So, we’ll have to do more to protect our crop.”

Making the rules
Besides potential poor red colour, the main downside of nets could be increased vegetative vigour and reduced reproductive bud development. This hasn’t yet been a problem for the Langkloof grower mentioned, who has been using nets for three to four seasons. Karolus pays careful attention to pruning for optimal light distribution and good bud quality. “We manage our canopies to be very light-friendly, as any tree must be,” he said. He also practices renewal pruning to ensure a succession of bearing wood. Strydom agrees with this approach. “You must replace old spurs because as spur systems get older, especially when there isn’t enough vigour, fruit size suffers,” he said. “So, prune according to a renewal plan, but still keep the balance.” The concern with the Disselfontein Celinas is that they are on BP1 rather than a less vigorous quince rootstock such as BA29. Strydom compared the trees to having two energetic little boys running around the house. “If there are no rules in the house, will they be good or bad?” he asked. “These trees are the same. You must control their energy if they’re going to do what you want – you have to set rules. And those rules are how you prune or don’t prune.” Strydom is inclined to prune less, as pruning removes fruit and promotes growth. Instead, he recommends more bending, breaking, and girdling. Karolus applies all these techniques to keep the orchard in balance.

Other interventions
Disselfontein is cold enough that rest-breaking treatments are not necessary. Karolus pulls out all the stops to achieve a good fruit set. He uses up to eight hives per hectare and has multiple cross-pollinating cultivars grafted onto the primary Packham’s Triumph cross-pollinators. Karolus also enhances the fruit set with a single gibberellin application at 30–50% full bloom. The pears are thinned manually to the optimal crop load for obtaining the all-important fruit size. “This year, we gave 49 kg of nitrogen in the summer and 60 kg in autumn, and 100 kg of potassium,” said Stander. Potassium is strongly linked to fruit size in pears. “We’re running at potassium leaf levels of 1.40–1.45%, which is on the higher end, and soil levels are 4–6%.” He pointed out that one of the advantages of early pear cultivars is that less water is required relative to later cultivars – the Disselfontein Celinas received about 4 500 m3 per hectare last season. However, growers should beware of under-irrigating, especially on later cultivars, as this increases the risk of red spider mites. According to the most recent Hortgro figures, Celina represents about 2% of the total area planted to pears in SA, so there is much still to learn about this cultivar. In addition to the field-day orchard, Disselfontein has a younger Celina block, giving a total of about 10 hectares of the cultivar. Karolus thinks Celina feels at home at Disselfontein. “This field-day block has good return bloom every year,” he said. “And the bud quality for next season is there again.”

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Acknowledgements
Thanks to Johnny Karolus and his team for hosting the orchard visit and Mico Stander and Christo Strydom for manning the site. Strydom stood in for Piet Nieuwoudt, the horticulturist for this orchard, as Nieuwoudt was at the Bronaar field-day orchard.

The orchard at a glance
Cultivar: Celina
Rootstock: BP1
Size: 5.3 hectares
Spacing: 4.0 x 1.5 metres
Planted: 2016