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Prevention Rather Than Crisis Reaction Protects US Horticulture Industry from Medflies

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(Photo: O. Zelaya/Programa Moscamed)

As far as the horticulture industry is concerned, one piece of fruit in a traveller’s backpack or a shipment of fruit arriving at a seaport both portend disaster if the fruit also contains hitchhiking larvae of the Mediterranean fruit fly (medfly) – larvae that could escape inspection at port of entry and initiate an infestation. In the past, California and Florida, the main USA horticulture-producing states, used a reactive approach to control medfly outbreaks, such as ground and aerial insecticide- bait spraying – but this was only partially effective and there were concerns about negative public health and environmental impacts. In the mid-1990s, at the recommendation of a technical advisory committee in which staff of the Joint FAO/IAEA Division had a leading role, California and Florida both initiated the sterile insect technique (SIT), calling for area-wide preventive and continuous aerial releases of sterile male medflies over high-risk areas – an endeavour that has substantially reduced overall cost and prevented establishment of the pest.

Until the mid-1990s, California and Florida controlled medfly outbreaks mainly through using insecticide-bait sprays.

Yet, checks of surveillance traps increasingly found adult flies,indicating new infestations of the pest. The inadequate results of the reactive approach and concerns about its negative environmental and health effects led the two states to initiate a preventative medfly control operation – the sterile insect technique (SIT) – with the advice and technical guidance of the Joint Division.

SIT calls for rearing, sterilizing and releasing an enormous number of male medflies near where an infestation is or might occur. The males mate with wild females but there are no offspring. In the case of California and Florida, setting up a preventive SIT programme, and ensuring the weekly availability of millions of sterile medflies to release over the large areas at risk proved to be a challenge. The solution came from the largest insect rearing facility in the world – the El Pino facility of the Moscamed Programme  in Guatemala. Now, the hundreds of millions of sterile male insects needed to effectively cover the areas at risk are shipped weekly from Guatemala and delivered for release in the two states.

When California and Florida used a reactive approach – with increased insecticide-bait applications – medfly outbreaks were becoming ever more frequent and severe as a result of more infested fruit entering the states. It  meant exporters often faced costly quarantine restrictions from countries that only accepted shipments from medfly- free areas. Also at that time, insecticide-bait-based control programmes that used broad-spectrum organophosphate insecticides, such as Malathion, were facing serious public opinion opposition. In urban areas of Los Angeles, residents were extremely concerned about the insecticides wafting onto public property as well as their lawns and cars.

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