THE routine application of pesticides to vegetation in urban, natural and agricultural land in WA poses a threat to public safety as well as the environment.

The University of Western Australia’s (UWA) Institute of Agriculture organised a pesticide leaching workshop for fifty consultants, state and local government representatives and turf grass managers to discuss recent developments in pesticide risk assessment and regulations.

Polution from routine pesticide use has become a fact of life in WA. The pesticide leaching workshop addressed recent developments in risk assessment and regulations.
Image: USDA-ARS

Professor Christoph Hinz and Dr Gavan McGrath, both from UWA’s School of Earth and Environment, co-presented the workshop.

“Potential impacts such as the contamination of our drinking water supply, dermal contact by children in parks and playgrounds, inhalation of spray drift and environmental effects, such as those on frogs in our surface water bodies, lakes and rivers, can’t be ignored,” Dr McGrath said.

“There is a need for a formalised, agreed risk assessment procedure, including an evidence-based evaluation system and effective data collection in order to manage risks.”

Prof. Hinz said the biggest challenge was managing the many pathways through which pesticides can migrate, including through the air, sediment, ground water and surface water.

“The turf people were worried because the recent dolphin deaths in the Swan River have been partially attributed to emissions into the water,” he said.

“The two factors that govern how a pesticide interacts with soil are the stickiness of it to adhere to the soil particles and how quickly it degrades.

“If it is not retained very much and doesn’t degrade it is more likely it will reach ground water. If it is highly retained and degrades quickly, the risk is lower.”

Another problem with pesticide risk assessment is the occurrence of a single significant event such as a storm.

“Pesticides are usually applied when it’s dry, but a week or two later it rains and with the water may go a flood of water to highly conducting zones in the soil carrying contaminants into surface and ground water. More than fifty percent of pesticide leaching is caused by single events”.

Prof. Hinz said experiments done in Germany using a lysimeter to measure leachate found that factors such as the storm duration, intensity and inter-storm period affected pesticide leaching.

“So we can use rainfall statistics to do a better predictive job here in WA.”

As well as knowledge of soils and water behaviour, pesticide risk assessment requires data on pesticide properties.

“We need to integrate existing data available through different state government departments into a user-friendly management system for pesticide users.”

 Prof. Hinz and Dr McGrath said the UWA workshop which brought together researchers, regulators and pesticide end-users was a first collaborative step towards a better pesticide risk management tool.

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