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Patrick Mwanza and Gill Dealtry with the fruits of their research

When you walk into the supermarket and buy a pocket of oranges, you probably aren’t thinking about nanotechnology – but a great deal of science goes into getting those oranges into your supermarket trolley.

Some of that science is happening at the Nelson Mandela Metropolitan University (NMMU) Centre for High Resolution Transmission Electron Microscopy (CHRTEM). But before we talk about that, let’s go back to the orange on the tree.

A bright navel orange hangs from a leafy green tree. As the name suggests, there’s a navel-like indentation where the orange is attached to the tree. This navel is particularly attractive to an insect called the false codling moth (Cryptophlebia leucotreta); and she’s likely to lay her eggs here. When the larvae hatch, they feed on the fruit, damaging it and making it unsuitable for sale.

The traditional solution is chemical pesticides – but NMMU researchers, led by Dr Gill Dealtry and Prof Mike Lee with Dr Sean Moore (of Citrus Research International, River Bioscience) are working to improve what we know about an alternative, more environmentally friendly solution. A baculovirus known as Cryptophlebia leucotreta granulovirus (or CrleGV for short) specifically targets the false codling moth larvae. By spraying fruit trees with the helpful biopesticide CrleGV, farmers can control the false codling moths and the damage they cause. But how often do they need to spray the trees?

Just as the UV radiation in sunlight can damage our bodies, causing sunburn, it could also damage CrleGV. When that happens, the virus would need to be resprayed regularly onto the crops in order to ensure that there are sufficient quantities of the active virus to target the false codling moth. New research by student Patrick Mwanza uses the HRTEM to reveal how UV radiation causes the granulovirus to break down.

By examining ultra-thin samples of the granulovirus with the HRTEM the scientists are able to identify how the structure of the virus is impacted by UV light. “Until now,” says Dr Dealtry, “there has been no objective scientific information on how long the biopesticide remains effective.” Nanotechnology is helping to change that, and finding greener ways to move oranges from orchard floors to supermarket trolleys.

Writer: Charlotte Hillebrand