Minimising the off-site impact of pesticides from agricultural systems - a risk based approach

Philippines

Dr Rai Kookana
Phone: 08 8303 8450
Fax: 08 8303 8565
Email: Rai.Kookana@csiro.au

• University of the Philippines at Los Banos, Philippines
• CSIRO Mathematical and Information Sciences, Australia
• University of South Australia, Australia

$470,989

01/01/2001 - 31/12/2003

01/01/2004 - 30/06/2005

Dr Ian Willett

Over the last two-three decades pesticide use has increased in both Australia and the Philippines. In the Philippines, during 1977 and 1991 total pesticide use increased from 3738 to 10,773 tonnes. The three important crops using pesticides in the Philippines are vegetables, banana and rice. While the total use of pesticides in rice is the largest (due to a large area under rice production) pesticides are most intensively used in vegetable crops. Pesticide sales in Australia also increased, from A$166 million in 1981 to A$1107 million in 1997, which indicates that pesticide use has significantly increased during the period - in particular for cotton, horticulture (fruits and vegetables), rice, sugarcane, grains and oilseed crops.
Pesticide usage patterns differ markedly between Australia and the Philippines. In Australia the dominant use of pesticides is as herbicides (65%), whereas the insecticides are the most commonly used group (46%) in the Philippines. Although growers in the Philippines are changing to less toxic pesticides, the majority are generally highly toxic to fish. Furthermore, these pesticides also show a high potential to bioaccumulate in fish and other aquatic organisms. Conditions of terrain and climate in the Philippines could also exacerbate the problem of off-site migration and adverse impact of pesticides. Steep slopes and heavy rains lead to severe flooding and high erosion losses; the risks in these situations of off-site migration of pesticides and threats to water resources are relatively high.

The project aims to develop modern risk-based approaches for reducing off-site impacts of pesticides applied to field crops, in order to protect human health, fisheries and aquatic ecosystems. This involves integrating information on pesticide use, site conditions, and the environmental fate and behaviour of pesticides in selected catchments in the Philippines and Australia. Scientists conducted a risk assessment of off-site impacts of agricultural systems, using tools such as CSIRO's Pesticide Impact Rating Index (PIRI), to integrate factors for use by water resource managers, policy makers and community organisations.

Project scientists sought to provide a framework for balancing the threats to water bodies against the continuing pressure of intensive agricultural and horticultural industries. They developed an inventory of pesticide use patterns and practices under different land uses in selected catchments in the Philippines and Australia. Risk assessment tools, such as CSIRO's Pesticide Impact Rating Index (PIRI), were employed to facilitate integration of different factors for easy adoption by water resource managers, policy makers and community organisations (NGOs).
The project team sought a better understanding of the environmental fate and ecological impact of selected pesticides on land and water resources in the two countries. This involved an assessment of pesticide impact on water resources that took into account the toxic load and transport pathways for pesticide migration in the selected areas. The scientists customised and validated PIRI for tropical conditions (mainly for the Philippines and also for tropical Queensland).
Training of Filipino scientists, regulators and catchment management personnel in risk-based approaches to pesticide usage in cropping systems was a significant component of the project.

The team compiled an inventory of pesticides used and application practices for different land uses in the Laguna and Taal Lake area, in the Philippines, in the 6th Creek sub catchment, Mt. Lofty Ranges, South Australia and in the Ord River Irrigation Area, Western Australia. Three separate booklets were published, each one containing the PIRI assessment where a range of scenarios was considered. Information was also given about aspects of variability in data collection and pesticide use. A summary of major chemicals of concern, due to a high risk of off-site migration or risk of adverse ecotoxicological impact (as determined by PIRI), was provided for each land use investigated.
Three training courses were run in the Philippines, assisting the transfer of the risk-based approach including PIRI to resource managers (particularly government regulators and organisations involved in catchment management and integrated pest management (IPM) programs). Filipino colleagues were also trained in protocols for assessment of environmental fate and effects of pesticides, namely (i) to conduct pesticide sorption studies and (ii) ecotoxicological studies using organisms that are relevant to their environment - especially shrimp (Macrobrachium sp.), juvenile fish (Tilapia sp.) and native duckweed (Lemna sp.). The training sessions gave an opportunity to identify and overcome problems encountered with specific experiments, enhancing the capacity of the project team and adding valuable Philippine-specific information into the database.
A better understanding of environmental fate and ecological impact of selected pesticides on land and water resources in the Philippines and Australia was developed from studies in Australia on the sorption behaviour of selected pesticides in tropical soils from Australia and the Philippines and temperate soils from the Mt. Lofty Ranges, Australia. Also, ecotoxicological studies using species relevant to the Philippines have provided valuable data for customising PIRI for the Filipino conditions.
The assessment of pesticides impact on water resources in the Philippines was only done in a broad preliminary manner where the pesticide toxicity data for selected local aquatic organisms were compared with pesticide residue levels obtained from grab samples collected twice a year. In Australia, a more comprehensive assessment involved ecotoxicological analysis of samples collected from aquatic ecosystems. But in both cases it was not possible to quantify loads of pesticides moving off-site, due to lack of flow data. The toxicity tests on aquatic organisms showed that some of the pesticides detected in waterways in the Philippines and Australia are below the levels that produce acute toxicity. But they still can have chronic toxic effects (e.g. abnormalities in susceptible newly hatched fish larvae).
Strategies for both Filipino and Australian conditions were suggested that minimised off-site transport of pesticides. Pesticides with high, medium or low risk rating were identified for various land uses in both countries. In Philippines, simple measures such as plugging the leaking bunds in rice paddies were suggested to minimise direct pesticide migration into adjacent drains and stream. In Australia, measures such as light incorporation of pesticides in soil after spraying were recommended, but assessment of the efficacy of these strategies was beyond the scope of this project.
In the Philippines and Mt. Lofty Ranges, South Australia, pesticides were monitored at several locations in the main creeks and rivers. Certain pesticides (e.g. diuron, butachlor, simazine, herbicides and chlorpyrifos, methamidophos and pyrethroid insecticides) were detected in sediment and water samples in both countries. The monitoring program was intended to provide a snapshot assessment to establish if the pesticides were moving off-site or not and was not designed to quantify the loading from a selected land-use. Therefore, the potential risk they posed to organisms in the rivers and the receiving lakes are not clear at this stage. The detected pesticides and other pesticides identified in the PIRI assessment will provide the basis for future work to develop management strategies to minimise off-site migration.