Autumn 2012 True Natural Health Magazine – Your Questions Answered
By Roger French


QUESTION:   A decade ago, mangoes were being dipped in a toxic chemical to prevent attack by Asian fruit fly. Is this still the case, and, if so, should we stay clear of them?



I am advised that some post-harvest chemical control is still being carried out for fruit fly. For the fruit fly-free states of Australia – Victoria, South Australia and Tasmania – this is mandatory. In other states, it is up to the individual grower or packing house as to whether they apply fruit fly control or not.

The control involves dipping or spraying mangoes in one of a range of approved pesticides, all of which are toxic to insects as well as to humans. The important and difficult-to-answer questions are how much chemical is absorbed into the flesh of the mango and how toxic is the chemical. Fruit fly chemicals are systemic, so some at least must be absorbed through the skin of the fruit.

The chemical that has been most commonly employed for many years is dimethoate. It was used both as a pre-harvest and post-harvest insecticide to control many common insect pests in a wide range of vegetables and fruit crops. This included fruit fly control in many areas of Australia and the destruction of Queensland Fruit Fly before fruit is permitted to be traded interstate. Dipping mangoes in solutions of dimethoate has been found to be highly effective against fruit fly.

But its use was suspended in October 2011 following a review by the Aust. Pesticides and Veterinary Medicines Authority (APVMA) that led to concerns about possible effects on human health and trade. Some of the estimated exposures for consumers were found to reduce, although not breach, the standard margins of safety. These safety margins are designed to ensure that we will not be exposed to high levels of residues in food.

The APVMA has recently issued several permits for alternatives to dimethoate in certain crops. A prominent one for fruit trees is trichlorfon, registered for use in all states.

Trichlorfon, an organophosphate insecticide, is a nerve poison and highly toxic. It is selective, meaning that it kills selected insects, but spares most other organisms. A fortunate aspect of trichlorfon is that it is rapidly excreted, about three-quarters being eliminated in the first twelve hours after exposure.

Also registered for fruit fly control is fenthion (Lebaycid), although growers are advised not to consider it a permanent replacement for dimethoate. Fenthion is also under review because of possible food safety and environmental concerns. It has been in use for a long time and is a very toxic chemical.

I was pleased to hear from a spokesman for the Aust. Mango Industry Association that they are moving towards Integrated Pest Management in which no toxic chemicals are involved.  

I have not answered your question fully because it is almost impossible to discover just what chemicals are currently being used. Firstly, individual growers are spread over thousands of kilometres and act individually within overall regulations. Secondly, in the maze of information about pesticides, it is difficult to discover just what is available for mangoes and what is most commonly used.

Like all food crops that are not organically grown, mangoes may contain traces of pesticides. Unfortunately, those pesky, destructive fruit flies are so difficult to control that strong chemicals are needed.

As a mango lover myself, I intend to continue enjoying about five mangoes a week as part of a Natural Health way of eating. In case there are minute traces of nasties, I gain peace of mind from the fact that there are high levels of antioxidants in the abundant veggies and fruits I consume.