Cotton Pesticides in Perspective: Minimizing their Impact on Produce and in Riverine Ecosystems
Feb 12, 2019

WCRC WCRC2 Cotton and Environmrnt

ABSTRACT
Despite measures taken to reduce reliance on chemicals (e.g. Ingard cotton), production of Australian cotton still involves significant inputs of pesticides, with the potential to contaminate other agricultural produce and riverine ecosystems. Since 1993, the environmental fate and transport of pesticides used in cotton growing have been extensively monitored to minimize their impact as chemical residues. This research has focused on endosulfan as the major insecticide applied on cotton farms, and as a model for other chemicals. Positive results of the research that can help provide more sustainable practices are:

Information on field dissipation of endosulfan, in farm soils, surface water and on nearby pasture. In summary, dissipation of endosulfan from cotton fields occurred mainly by volatilization in the first 2-3 weeks after application; endosulfan isomers on cotton plants and in soils are quickly metabolized, with half-lives of 3-4 days. Two weeks after application, only 2-3 % of the amount applied in one spraying remained in the foliage. Unfortunately, there is some persistence of the metabolic oxidation product endosulfan sulphate in the field, with a ‘half-life’ in soil of about 100 days. However, by the start of the new growing season only 1-2% of the endosulfan applied remained on field as endosulfan sulphate, so there is little or no long-term accumulation.

A study of the degradation of endosulfan on pasture showed that residues fell to acceptable levels within about 3-4 weeks, dependent on the distance from the line of spray application. Runoff waters contain 1-2% of total endosulfan transported or dissipated off field in one season, major storms accounting for 50% of this amount; the relative significance of lateral rather than vertical leaching of soluble chemicals in grey-cracking soils (Vertisols) is emphasized.

Immunoassays (ELISA) provide rapid, inexpensive, field tests for pesticide residues, providing more comprehensive data-sets that allow decisions on the release of contaminated water and the assessment of the progress in remediation.

Field research protocols needed to generate data for registration purposes have been developed.

Significant progress towards safer use of pesticides in cotton growing, resulting from the preparation of a database indicating risk factors with specific pesticides and herbicides and a better understanding transport mechanisms. The adoption of better management practices that reduce these risks is already contributing to more sustainable cotton production.


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