The value of pest monitoring for the economic sustainability of South African apples for the export market
Date
2023-12
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Stellenbosch : Stellenbosch University
Abstract
ENGLISH SUMMARY: There is a risk of market closure for South African Fuji apples due to phytosanitary pest interception. Pests that are proving problematic in our local climate include codling moth (Cydia pomonella), mealybug species (Planococcus citri, Pseudococcus longispinus and Pseudococcus viburni), mites (Panonychus ulmi and Bryobia) and woolly apple aphid (Eriosoma lanigerum). This is problematic due to this market paying a large premium for these fruits, not realised elsewhere and otherwise making this widely planted variety significantly less profitable to produce. While applying more pesticides to reduce pest presence is effective, it reduces environmental and economic sustainability. A 25-tree per two-hectare monitoring program was applied to address this issue, alongside codling moth trap counts, a preharvest assessment and packhouse fruit sampling. This was applied to 264 Fuji orchards across the Elgin, Grabouw, Vyeboom and Villiersdorp (EGVV) area. Data was collected biweekly and analysed using various methods appropriate to the data type. The findings of this study showed that both using this monitoring program effectively or using an aggressive spray program significantly reduced the occurrence of mealybug while woolly apple aphid was best managed using regular monitoring. Mite and codling moth presence were unaffected. Mites were shown to be managed efficiently through the use of natural predatory mites. Woolly apple aphid, while having high levels of parasitism by A. mali, was still a hindrance to export due to mummies left on fruit. The preharvest assessment showed to be significantly more effective at reducing risk when allocating orchards to a particular market, when compared to the use of a packhouse sample. Various orchard environmental factors were identified as being influential on each of the phytosanitary pests’ presence. Financial data used in partial budget modelling revealed that the use of monitoring to reduce risk of phytosanitary pests could result in a 62% increase on return on investment of annual costs per hectare. These findings show that implementing holistic monitoring systems can aid in reducing the risk of market closure while simultaneously improving growers’ financial standings and better serving the environment. Further research should be aimed at studying seasonal differences in phytosanitary pest pressures and what impacts this may have as well as place focus on industry leaders to make trade more sustainable and less volatile to closure.
Description
Thesis (MScAgric)--Stellenbosch University, 2023.