This division started the investigation for the selection and evaluation of especially clonal rootstocks for deciduous fruit trees in South Africa. The release of imported as well as the locally bred pear rootstocks (BP1, BP2 and BP3) and plum rootstocks (Maridon and Intec 2) are some of the main research activities of this division. Today rootstock approach in this division is multidisciplinary, including horticulturists, plant physiologists, plant pathologists and entomologists.
Currently a detailed recommendation for a specific situation can be made that will include the effect of the rootstock on the scion cultivars as far as precocity production and fruit quality aspects are concerned. Information on resistance of the rootstock to pests is diseases are also available. Rooting techniques for rapid production of nursery trees is simultaneously developed and possible rootstock-scion affinity is identified.
This division was responsible for the installation of over sixty automatic weather stations in the major deciduous fruit producing areas of the Western and Eastern Cape. Most of these stations are linked to a central computer at Infruitec and data is collected at weekly intervals. As a routine service to deciduous fruit producers data is used for the calculation of cold units, growing degree hours and the calculation of leaf wetness which is used in the apple scab production model. Results of these calculations were related to phenological data collected by pomologists, entomologists, pathologists and physiologists.
Currently the climatic data is used in all instances where production models were applied and tested. Examples where climatic data is currently used in prediction models are the fruit size prediction model, the prediction of the incidence of oriental fruit moth and codling moth, the prediction model for apple scab and the prediction of stem-end russeting of Golden Delicious apples. The development of the apple fruit size prediction model and the stem-end russeting prediction model were also developed in the Horticultural division and are used throughout the apple industry of South Africa. Prediction models that are currently being developed include a model for superficial scald of Granny Smith apples and a model to predict storage ability and fruit quality.
Various new fruit crops have been imported and evaluated under South African conditions. Some of these crops are pistachio nuts, walnuts, cherries (rootstocks and cultivars), olives, persimmons, blue berries, raspberries, dates and kiwi fruit. This division is also responsible for the evaluation of different cultivars and new crops like honeybush tea and the development of cultivation practices for these first phases of the development of and organized industry of the individual crops.
This division made a substantial contribution in the identification and application of artificial rest-breaking chemicals in deciduous fruit areas where a lack of enough chilling units prevails. Methods were developed where rest breaking chemicals in combination with specific thinning chemicals can be used. Lately a wide variety of environmental friendly rest-breaking chemicals are under evaluation in the search for alternative methods to control delayed foliation.
The importance of tree shape and crop control for regular cropping to ensure fruit quality and maintaining high density orchards early in the sixties and seventies was illustrated by researchers in this division. Since then, various methods of fruit thinning (including chemical thinning), pruning and planting and training methods were evaluated and improved for the various cultivars of pome and stone fruit to optimize the production and quality of the individual cultivars and to maximize net farm income. This information is regularly relayed to relevant producers at lectures, symposiums and field days.
Guidelines were compiled by researchers in this division to optimize the growth and production of pome and stone fruit nursery trees after establishment in an orchard. The better growth and an early crop of fruit trees will ensure an early recovery of establishment cost of the orchard.
Control methods were also developed and relayed to the relevant producers regarding the elimination of certain physiological disorders of deciduous fruits. Some of these disorders include, calyx-end russeting of Golden Delicious apples, knobbliness of pears, woolliness and gel-breakdown of peaches, nectarines, plums and apricots.