1992: Thorpdale (Vic) Dieldrin “Control Area”

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 It was subsequently found to build up to toxic levels in animals and humans and was withdrawn from use in 1987.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