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.
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 It was subsequently found to build up to toxic levels in animals and humans and was withdrawn from use in 1987.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 2010http://www.cardinia.vic.gov.au/files/Strategic_planning/SP_GWMP_NorthernRanges_IssuesPaper_2010-06.pdf