Crop Production Programme

Research on this theme is aimed at understanding the progression of dormancy under mild winter conditions and the impact of insufficient winter chill on fruit production.  We also study dormancy release to potentially identify new, safer rest-breaking chemicals.

Prof S Midgley completed a project that provided an indication of how climate change during the winter and early spring period might affect pome and stone fruit production in different regions. This information will be incorporated in Hortgro’s climate change App.

Finding more precocious and productive rootstocks adapted to South African conditions is integral to our orchard of the future vision. For this reason, various pome and stone fruit rootstocks are evaluated in an increasing number of industry trials in commercial orchards.

New apple rootstock evaluation sites were planted to dwarfing rootstocks at three locations in the Highveld region where Western Cape results are not applicable due to the milder summer climate, planting under nets and fertile soils. Louterwater Granny Smith trees on rootstocks varying in vigour were planted in two production regions with warm winters to assess their effect on bud break and flower synchronization. Together with a Granny Smith trial planted in 2022 in the Langkloof, these plantings will also be used to assess the effect of rootstock on green colour development.

Other rootstock research is aimed at characterising new rootstocks in terms of adaptation and disease and pest tolerance. Various projects are evaluating the susceptibility of rootstocks to Phytophthora, Rosellinia, woolly apple aphids, plant parasitic nematodes and replant disease. A new project was initiated to study the cause of galls on apple nursery trees and rootstock susceptibility to crown gall. Another new project will be comparing the performance of tissue culture-derived apple and stone fruit trees against those produced from layers or cuttings, respectively.

Prof Stephanie Midgley determined that trees on dwarfing apple rootstocks are not necessarily more sensitive to water deficit than trees on more vigorous rootstocks. Trees on dwarfing rootstocks had a much lower water requirement on a hectare basis and had a much higher water productivity, i.e., Rand income generated per cubic meter water transpired. Dr Xolani Siboza finalized a report on a rootstock evaluation trial consisting of adjacent more dwarfing and less dwarfing plantings at three locations with Fuji as scion. Rootstocks from the Cornell Geneva programme like G.778, G.228 and G.202 outperformed industry standard rootstocks.

Chad van Wyk completed two peach/nectarine and two plum rootstock evaluation trials. The results of these trials will be incorporated into the stone fruit rootstock tables first published in issue 6 of the Fresh Quarterly (www.freshquarterly.co.za).

Of the “serious” pome fruit producers, South Africa, together with Brazil, has the production regions closest to the equator.  This means higher summer temperatures and generally, altogether more plant stress and more fruit downgraded for processing compared to our major competitors.

The great inefficiency of caring for fruit that ultimately ends up in a juice bin significantly impacts the profitability of the South African industry, especially under the serious cost squeeze conditions that the industry is experiencing.  It should not be surprising that research under this theme is predominantly aimed at decreasing sunburn and internal fruit quality defects brought about by climatic stress.

A new project utilizes the ProHort ecophysiology platform to study the innate ability of different apple genotypes to tolerate high light and heat. Prof Lee Kalcsits of Washington State University is a collaborator on the project and participated on the project while visiting South Africa on his sabbatical. Dr Tara Southey of TerraClim launched a pilot project to determine the possibility of developing suitability maps for new plum cultivars.

Jason Ladegourdie’s project showed how Packham Triumph growers may benefit from draped nets while Tara Southey generated high resolution topographical and climatic maps for the EGVV, Langkloof and Ceres production regions. These maps can be of great assistance in site selection for new plantings.

Research in this field is aimed at obtaining regular high yields of good quality fruit.  Hence, projects tend to investigate flower initiation, pollination, fruit set, fruit thinning and alternate bearing.

Louisa Blomerus completed a project that investigated the effective pollination period (epp) of different plum cultivars. Her research shows the considerable variation in the duration of the epp from three days in Songold to more than 10 days in Laetitia. We advise that all new plum cultivars are screened for their epp to provide producers with an idea of how consistently a cultivar may set and allow them to plan accordingly.

Research in this theme focuses on orchard mechanization and technology drivers such as big data, remote sensing, robotics, and GIS that will all contribute to changing the way we produce our fruit in our orchards of the future.

Water availability was identified as one of the top five risks facing our industry in the future.  The Western and Eastern Cape provinces are water scarce; climate change is driving a drying trend and competition for water is increasing.

The crop production water strategy involves 1) determining how much water highly productive deciduous fruit trees use, 2) conducting research on various water-saving technologies and 3) conducting research to show growers the negative effects of over-irrigation on production and quality.

We are currently co-funding two projects with the Water Research Commission to determine the water requirements of high-yielding plum and pear orchards.

Engineering consulting firm Zutari was commissioned to develop a water strategy for the South African deciduous fruit industry incorporating the results of a completed study that characterized groundwater availability and groundwater use within the main Hortgro production areas. A study by Daniël Viljoen showed that moderate to severe water deficit has little impact on the storability of Fuji and Golden Delicious apples but might increase internal browning in Cripps Pink apples.