The false codling moth causes substantial financial losses to citrus crops in South Africa every year, so it seems counter-intuitive for farmers to willingly release tens of thousands of them over their plantations.
But this is exactly what citrus producers in the Sundays River Valley, such as Habata Agri, are doing in the ongoing war against an insect that has become resistant to traditional pesticides.
Habata operations manager Gary Webb explained that the release of the moths was the end result of a project initiated by Citrus Research International (CRI), who looked into the use of a pest control measure known as the sterile insect technique or SIT.
The project’s trials were so successful that Xsit, who now breed and sterilise false codling moths for release among citrus crops, were established in November 2006 to fast-track commercialisation.
Once released, the insects interbreed with the wild, fertile variety and, in doing so, the overall population is reduced.
Webb explained that these insects, known as FCM among farmers, were a major pest that could lead to significant crop losses.
“They lay their eggs on the skin of the fruit and when they hatch the larvae burrow inside,” he said.
“Once the fruit has been penetrated it is more susceptible to mould and other diseases, often discolours around the hole and is more likely to drop from the tree.”
A female moth can lay up to 800 eggs over her lifespan and Webb said nearly three quarters of the South African citrus export markets had declared FCM a phytosanitary pest.
Xsit managing director Sampie Groenewald said the moths, which were bred and sterilised at a plant in Citrusdal, were transported to the different regions in cold trucks before being loaded onto small planes and distributed over the orchards.
He said their moths, which were used on 19 000 hectares across the citrus, stonefruit and table grape industries, had a red dye added to their diet to ensure positive identification in the field.
“Trap data is collected from the orchards, which provide an indication of the wild and sterile populations.”
He said the moths were released over a period of 10 months – from September to June.
The use of SIT could effectively lower the host FCM population in fruit orchards to a level that was no longer an economic concern for producers, according to Groenewald.
FCM SIT data monitoring and analysis, he said, was fully compliant with the requirements of the proposed “Systems Approach to FCM Management” as an alternative to cold sterilisation of fruit for export markets.
“The sterile insect technique is not only very effective, it’s a biological product with zero impact on the environment and one that leaves no residual chemicals on the fruit.”