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Global zoning for pesticide residue behaviour

Fruit and vegetable growers are set to be among the beneficiaries of international proposals to set up global zoning for pesticide residue behaviour. Those who are likely to benefit particularly are farmers who grow more minor crops such as olives or lettuce, according to MAF Food’s National Manager (Plant Residues), Dave Lunn.

Under the scheme, the world would effectively be carved into different zones for the purposes of using residue trials to measure pesticide residues in food, an important part of the pesticide registration process in most countries.

This means that each individual country should be able to accept data from trials carried out in other ‘similar’ countries instead of the current practice of insisting that at least some of the testing be done at home. In New Zealand’s case, the present system normally requires that at least half the pesticide residue trials be done within this country.

This creates delays in getting new  pesticides into the marketplace (while these trials are being conducted) and in some cases can even result in the most appropriate pesticides not being available because the cost of doing local residue trials is too high.

For instance, in the areas of pesticides for minor crops, it often isn’t worthwhile for a chemical company to carry out residue trials here for what may be a relatively small market. It can cost thousands of dollars to add a new crop to a pesticide label.

Under the scheme, New Zealand regulators should be able to accept data from trials done in any other country in ‘our zone’ and from a global perspective, other countries in ‘our zone’ should be able to accept New Zealand data.

Up till now, virtually all countries in  the world have wanted at least some of these residue trials conducted nationally, and these requirements have varied from country to country.

Dave Lunn says, "In Europe the general requirement is for eight trials while the United States usually ask for between one and 20 trials in up to 13 different regions. Other countries say ‘we don’t really have any hard and fast rules but as long as you can show the environment’s the same, we’ll probably accept overseas information’ ".

Therefore, regulators internationally have come up with a plan to cut down on unnecessary trials and pesticide residue-nationalism. Dave Lunn is part of an OECD Steering Group effectively looking at a global map to decide what areas of the world have the same environmental conditions and therefore where similar residue decay behaviour can be expected (see article on page 4). The work of this group has been strongly supported by the New Zealand fruit and vegetable growers’ organisations.

According to Dave, "Everybody is saying that our country is different from everybody else’s country. We say is there not a way of using a map to decide that when you’re spraying cabbages with a pesticide in certain areas, the residue behaviour should be the same and therefore we can use their data to support our use of that pesticide".

The group is looking at drawing up a tentative map of residue zones and over the next 6-8 weeks, finding enough residue data to plug into the map so they can see if the proposed zones can be justified.

Luckily the FAO has about ten years’ worth of residue trials on a range of pesticides and different crops, used internationally in setting maximum residue limits for pesticides, that the group can use.

The Steering Group plans to meet again in Holland next year to analyse the data and decide whether the initial zones are suitable or whether they will have to redraw the map and start again. If all goes well, the plan could be finalised by the end of 2002.

Dave Lunn says, "If things look good next year, we may even be able to change the ACVMG pesticide registration standards here in New Zealand to get the scheme up and running before the rest of the world".