Research: Fruit Production & Quality

Programme Coordinator:

Collaborating researchers involved:
Dr Paul Cronje, Jakkie Stander (CRI at SU), Teunis Vahrmeijer (CRI at UP)

Research is being conducted on:

1. Methods to reduce the size of the navel end opening of navel oranges

Navel end size is an important parameter for external fruit quality criteria in navel oranges. Fruit with big navels are not desirable and make fruit liable to attack by insects e.g. mealybug and false codling moth. Fruit splitting in navel oranges also starts at the navel end. We will use synthetic auxins to reduce navel end size and attempt to find the appropriate timing and optimum concentration for application. Smaller navel end openings will lead to increased packout percentages.

2. Improving the uptake and effectivity of foliar applied nutrients

In general, absorption of foliar applied nutrients on citrus trees is affected by environmental factors, factors related to the spray solution and biological factors. The objective of this study is to improve the uptake and effectivity of foliar applied nutrients by manipulating the concentration of different products, the pH of the spray solution, the adjuvants used and the formulations used. e.g., Improve the uptake of phosphate-formulations in order to reduce acidity of Valencia oranges, in which high acidity can be a problem in certain growing areas.

3. Economic benefit of hand thinning on citrus

Although hand thinning is a common practice in deciduous fruit production, not many citrus growers make use of this practice due to the fact that it is very labour intensive. Previous results indicated that a large proportion of fruit must be removed in order to affect fruit size positively. The objective of this study is to determine whether hand thinning results in any benefit, other than an increased fruit size.