In the late 1990s, scientists from the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture were working in south Africa on a programme to help table grape exporters apply the sterile insect against fruit flies, when growers told them about another damaging pest that was having an extremely negative effect on south African citrus exports – the false codling moth. The Joint Division in collaboration with the United States Department of Agriculture (USDA) joined the fight and, since then, has worked with partners in South Africa developing a new technology and establishing a public-private partnership to overcome the problem. By 2010, the programme was treating a 4000 ha citrus area in the Western Cape’s Citrusdal Valley, greatly reducing insecticide applications and infestation levels.
When it comes to fighting one of the most serious enemies of the citrus export industry in South Africa, it doesn’t matter if growers are rich or poor. Whether they have 1 ha of orange trees or 1000 ha, each farmer benefits from combating a common enemy – the false codling moth, a native of Africa and among the world’s most feared invasive pests.
The method used for managing the pest in orchards and surroundings – the sterile insect technique – is an environment-friendly method for the biological management of pest populations that is applied on a permanent basis in combination with other control tactics to suppress pests. As its name implies, the sterile insect technique calls for mass-rearing and sterilizing a large number of male insects and then releasing them weekly to mate with wild females who will then produce no progeny due to the males’ sterility. For this method to work, all growers must work together to ensure there is total coverage of the area.
The South African citrus producers asked the Joint Division to support development of the sterile insect technique for false codling moth, because insecticide-based control mechanisms had become ineffective. The insects had developed resistance to most existing pesticides, leading to increased applications of the chemicals. This not only caused health problems for field workers, it also left chemical residues on the fruit too high to meet export standards.
The false codling moth also represents a major phytosanitary barrier to exports. It is confined to Africa, but with greater cross-border trade increasing the chances of it showing up in other areas and global warming allowing its survival in previously inhospitable areas, many countries have set strict pro-active quarantines. For example, if the false codling moth establishes a presence in the southern and southwestern United States, it would cause multi-billion dollar losses. As a result, the USA has set up quarantines under which entire consignments can be rejected if single larvae are found, and conducts border searches so stringent that it reports finding one larva in a piece of fruit in a passenger’s luggage in 2009. The cost was also high for South Africa as an exporter. In 2004, the estimated annual loss incurred by the citrus industry of South Africa as a result of false codling moth infestation was US $14 million.
