Africa’s most powerful microscopes are being used to boost the use of bio-pesticides in South Africa’s citrus industry, writes Nicky Willemse.
Africa’s most powerful microscopes are being used to boost the use of bio-pesticides in South Africa’s citrus industry, writes Nicky Willemse.
Nelson Mandela Metropolitan University Masters student Patrick Mwanza, 26, is combining cutting-edge physics with real citrus farming practices to encourage farmers to wage an environmentally-friendly war against the False Codling Moth, one of the country’s main citrus pests.
With the majority of South Africa’s oranges exported to Europe, citrus farmers have to make sure their products are completely pest-free. To do this, some are reluctant to use anything but traditional chemical pesticides – but Mwanza is hoping his research will lead to greener farming.
Since 2004, the bio-pesticide Cryptogran – a product of River Bioscience, South Africa’s leader in biological pest control – has been used effectively to control the False Codling Moth.
Cryptogran is essentially a concentrated form of a naturally-occurring virus to which the moths are susceptible. Sprayed on the oranges, moth larvae newly-hatched from eggs laid on the oranges, ingest it and die.
Without pesticides, the larvae would burrow into the navel of the orange, ultimately causing “fruit drop”, said Mwanza’s supervisor Dr Gill Dealtry, a Senior Lecturer in the Department of Biochemistry and Microbiology.
“It’s absolutely critical that the moth is controlled. If just one orange is infested, an entire consignment may be deemed unsuitable for export,” said Dealtry.
The challenge when it comes to Cryptogran is that sunlight diminishes the virus’s effectiveness over time and, like most pesticides, it has to be reapplied every few months. However, until now, there have been no hard and fast rules about how long the pesticide remains effective and how often it should be reapplied, with most farmers erring on the side of caution.
Using the University’s new high resolution transmission electron microscope (HRTEM) – the most powerful in Africa – and it's scanning electron microscope (SEM), as well as the Raman spectroscope, Mwanza is able to examine the miniscule virus molecules to their very core.
The aim of this is to make the application of Cryptogran an exact science, leading to its optimal use and thereby saving farmers money by preventing over and under-spraying. It is also likely to lead to the wider use of the bio-pesticide, which will have positive implications for the environment.
Using samples from trial sites in the Sundays River Valley and also under UV light in the lab, Mwanza, who has completed a year of Masters research, has been able to determine that the virus’s protective covering offers no protection from UV rays – and his next step is to examine the core of the molecule to determine how and when this internal structure changes.
He has presented his findings at major microscopy conferences in South Africa, and says the driving force for his research is a passion to put science to practical use. “I’m a scientist helping the community."
Dealtry agrees: "This project provides an opportunity for unique collaboration between physics, biochemistry and role players in the citrus farming industry.”
Mwanza’s research is being funded by Citrus Research International, the research arm of the South African Citrus Growers Association.
