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This article was published in 2000
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Bananas, Local Councils & Dieldren Residues
Ian R. Harradine, District Veterinarian, Grafton
Introduction
Since the late 1970's dieldren residues have been found in cattle at slaughter following grazing of old banana plantations. Much testing of cattle, soil, bananas, banana skins, leaves, stools, pasture and compost has been conducted.
During June and July of 2000 two violations above Maximum Residue Limit was detected in cattle after 5 years without such detections. The reasons for these latest residues highlights new trends in the banana industry. The targeting of high-risk postcodes for residues was also a factor in these recent detections.
The economic downturn in the banana industry has seen many plantations close and revert to grazing. Current threats to the industry from cheaper imported bananas and poor local profitability will not reverse this situation quickly and is likely that many plantations will close down.
Local councils are involved in ensuring weed control, local environmental concerns and the future developmental control of contaminated lands.
Case Histories
1. Coffs Harbour Property
This property was already classified as a T3 high-risk properly. A PMP was in place since 1996 restricting cattle from known contaminated sites and timing cattle sales to coincide with good pasture. The owners had only 6 head of cattle on the property and rarely sells any of them.
Cattle are used on this property and many others in Coffs Harbour to keep the area mowed and reduce the risk of fire.
In June 2000 a calf and cow were slaughtered at Casino abattoir. The calf had a reading of 0.30mg/kg dieldren and the cow 0.19mg/kg.
On investigation, the herd had recently been turned onto a crop of bananas that had become weed infested and was no longer economical to continue to crop. The local council weeds inspector had given notice to the landholder to control the weeds on the hill and an obvious economical option was to turn the cattle on to it. Soil test results showed an average broadacre figure of 0.13mg/kg in the abandoned banana plantation where the cattle were recently grazed.
2.Korora Property
In July 2000 a beast with a dieldren residue of 0.58mg/kg was detected at Casino abattoir. This tag had been tested under the "M" program that targeted high-risk postcodes.
The cattle bad been gazing old banana ground that had not been cropped for the past 6 years. The soil in the paddock gave a reading of 0.97mg/kg and an area adjacent to the old, disused packing shed registered 0.67mg/kg. DDT was also detected in these soils at low levels.
This property had ceased banana production six years previously due to non-protitability of the enterprise. Cattle had been running on the contaminated area for all this time and a number of sales had occurred during this time without testing.
Local Council
A number of issues arise in respect of planning for future development of these contaminated lands, the request for landholders to control weeds and maintain the amenity of their properties. The Rural Fire Service also has concerns when tracks of land amongst houses become overgrown.
The extensive use of herbicide on these hills to control weeds is not an option with problems of drift to the inhabitants in the valley below. Cattle on the other hand while doing a good job of cleaning up an abandoned banana plantation do expose the steep slopes to significant soil erosion and the threat of landslides.
The subdivision of these contaminated lands has been going on for some time with common soil readings in these areas yielding around 1.0mg/kg dieldren. Councils have to decide on how best to manage these lands especially now that more will become available for sale as bananas are deleted.
Management
There is no doubt that the grazing of old banana plantations by cattle is a high-risk event for the likelihood of producing chemical residues in livestock. As a general rule, one should therefore not recommend it.
However, nothing is ever quite as simple as that and a more expansive approach must be taken to solve the problem. Some of the options discussed with landholders involve the following management plans:
• Grow another crop. Avocados, mangos or trees.
• Agist cattle away on clean country for 12 months prior to slaughter to deplete residues
• Maintain long, dense pasture to decrease the amount of soil ingested by stock and limit soil erosion
• Time the sale of cattle to correspond with good seasonal conditions when residues in stock are likely to be low because stock are fat and pastures are long.
• Run non-food producing animals on the land. Horses.
With large numbers of banana growers going out of production at present there is a good chance of more chemical residue detections in cattle from these properties.
Dieldren levels in soils from these properties has been slowly declining, although there is still many years to go before the majority of these properties can be considered clear.
Consideration needs to be given as to how properties can provide evidence after "R" status to show that environmental contamination levels have fallen to levels that no longer present a threat of causing unacceptable residues in livestock. This is the next stage where properties would nolonger need a PMP and the property can be given a "C" status.