1987-1988: The Dieldrin Contamination Issue: Gembrook (Vic)

The Dieldrin Contamination Issue

“…Until 1987, the organochlorine, dieldrin was used by potato farmers in several areas of southern Victoria to control insect pests such as wire worm (Gonocephalum pterohelaeus) and white fringed weevil (Graphognathus leucoloma). The traditional management system for these farmers is to rotate paddocks between potato cropping and sown grass/clover pasture. The sown pasture is usually used for grazing beef cattle over a period of. several years, before returning to potato cropping. When the dieldrin sampling at abattoirs intensified after the 1987 “dieldrin crisis”, many cattle from these farms were found to have fat dieldrin levels exceeding the Maximum Residue Level (MRL) of 0.2 parts per million (ppm). Further investigation found that the soil from many of the paddocks which these cattle grazed, was contaminated with measurable amounts of dieldrin…” (Source: SPATIAL DISTRIBUTION OF SOIL DIELDRIN LEVELS WITHIN DIELDRIN CONTAMINATED PADDOCKS IN SOUTHERN VICTORIA K.L. BUTLER*, H. SIMPFENDORER*, J. STEWART* and G. ROBERTS* Proc. Aust. Soc. Anim. Prod. Vol. 18). Farms across Victoria were quarantined, many in the Yarra River catchment.


Dieldrin’s use was prohibited in Victoria when it was found in a range of agricultural industries in 1987.
It was used in potatoes and bulbs for the control of the native click beetle. Since its identification, a national plan was devised for managing contaminated
areas (National Organo-chlorine Residue Management Plan).
Dieldrin is known to remains stable in soils by attaching itself to soil particles, and is reported to have a presence in soils for 30 to 50 years. Residue retesting in the area, indicates that contamination levels have not changed since 1987.
Dieldrin is an unresolvable issue for the area, there are no options, and so the area is stuck with the problem. During this period, growers and the community have learnt to live with it.
In Gembrook, 97 properties are reported to be effected by dieldrin (25% of the area), with a total of 228 properties having cattle on them (DPI, 2004).
Average levels found in agricultural soils in the area are approximately 3.5 ppm (EPA consider this to be a low level). This level is satisfactory for everything other than agriculture.
The main concern with dieldrin is with cattle, as they readily take up the chemical and store it in body fatty tissue. This is an important problem for potato growers, because part of their rota tional cycle is to rest paddocks as pasture, and to run cattle on them. To reduce the dieldrin build up problem in their cattle, they must agist their cattle on clean country for 6 to 7 mo nths to decontamination them. This practise means that farmers loose money on their cattle because they can’t be sold in prime market condition.
Other animals such as sheep metabolises dieldrin much more quickly and are not as likely to find their wayonto residue sensitive export markets.
Unpublished research undertaken by DPI, suggests that dieldrin is not taken up by the vascular tissue of plants, but can be assimilated into leaf tissue of plants grown close to the soil through a volatilisation process eg. green tea or mint.
Dieldrin represents a problem for hobby farmers who run cattle on small properties because they are generally not in a position to agist cattle off site.
Tracing cattle from hobby farms is also a problem for regulatory authorities. Problems with cattle on small hobby farms became a problem in the in Stanley area (similar red soils to Gembrook).
Crops and livestock that are less prone to contamination are: vines and tree crops, regularly cut lucerne, horses and sheep. Enterprises susceptible to contamination are: cattle, ground foraging birds (emus, ostriches, ducks, free range chickens).
Source: https://www.cardinia.vic.gov.au/files/Strategic_planning/SP_GembrookRuralReview_TheFutureOfTheGembrookPotatoIndustryAndOtherLandUseImplications_2004-03.pdf
2.2 Potato growing
Potato growing in the Gembrook area has historically been the main form of agriculture in theNorthern Ranges Green Wedge, with an excellent reputation for high quality produce based onstrong consumer demand for brushed potatoes from the red soil country. In 1995 Gembrook accounted for around 4 per cent of Victoria’s potato growing area, producing around 10,000 tonnes and occupying around 400 hectares.
Unfortunately the area has been faced with majordifficulties over the last 30 years. Dieldrin is present in the red soils and much of the area is also affected by an organism called the potato cyst nematode (PCN). These two separate problems have combined to create an immensely difficult situation for many growers, some of whom are concerned about their future in the industry and their future options for retirement.
Potato cyst nematode is common in Europe while Australia has generally remained free of the problem. It consists of a microscopic organism which lives in the soil and attacks the roots of potatoes and some other plants. It is not a human health issue except it reduces crop yields, increases production costs and reduces the value of potatoes grown in the area. It was discovered in Western Australia in 1983, in Wandin (1991) and then in Gembrook in 1992. Since 1992 the Department of Primary Industries has declared four “Control Areas” in Victoria – at Thorpdale, Koo Wee Rup, Wandin and Gembrook – and movement into and out of these areas is restricted and export to interstate markets has been banned. The effects on the Gembrook potato industry have been devastating as Gembrook’s main market was interstate and as a consequence half the growers left theindustry and the production of potatoes declined in the study area by half.

At present only 12 potato growers now remain in the study area. Another problem in the study area is dieldrin, as a result of widespread use of the pesticide between1950 and 1980. At the time dieldrin was hailed as an effective pesticide which could   replace Dichlorodiphenyltrichloroethane (DDT) and it was used widely across the world. It was subsequently found to build up to toxic levels in animals and humans and was withdrawn from use in 1987. The level of dieldrin soil contamination does drop over time – reportedly 30-50 years before it is graded at a safe level – although the levels re main at unacceptable levels in the Gembrook area.Whilst soil contamination does not directly affect the growing of potatoes and other vegetables, itlimits options for cattle, ducks and free range chickens (but not for horses and sheep). Cattle whichgraze on contaminated dieldrin soils must be agisted on “clean” soils for six months before they can obtain a clean bill of health and be sold at market.

Source: Northern Ranges Green Wedge Management Plan Issues Paper June 2010https://www.cardinia.vic.gov.au/files/Strategic_planning/SP_GWMP_NorthernRanges_IssuesPaper_2010-06.pdf