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Modelling pesticide residues on greasy wool: experimental studies


Campbell, NJ and Hanrahan, PD and Russell, IM and Roberts, GS and Horton, BJ, Modelling pesticide residues on greasy wool: experimental studies, Australian Journal of Experimental Agriculture, 38 pp. 441-449. ISSN 0816-1089 (1998) [Refereed Article]

DOI: doi:10.1071/EA98047


A model has been fitted to results from experimental application of organophosphates, synthetic pyrethroids and insect growth regulators to sheep mostly in long wool. The model relates the rate of breakdown of pesticide to the chemical used, the method of application and the length of wool at the time of treatment. A genetic algorithm was used to combine a range of experimental results for each chemical group to determine the rate of breakdown, and also the effect of application method and length of wool on breakdown. Organophosphates break down very quickly when applied to the surface of the wool (initial half-lives of 9-12 days), but the rate of breakdown gradually slows as the proportion of pesticide near the surface of the wool decreases. When the pesticide is applied deep into the wool by hand jetting or dipping, the rate of breakdown is slower (average half-lives of 27-42 days) and more uniform. Synthetic pyrethroids applied by hand jetting or backliner to sheep with 6-9 months wool growth initially break down with half-lives of 32-39 days, but the rate of breakdown decreases to 59-215 days giving average half-lives of 48-103 days over the 3-6 months between application and shearing. Cyromazine applied by hand jetting to sheep with 6-8 months wool growth has an average half-life of 79-96 days, but less if applied by automatic jetting race. The other insect growth regulators have longer half-lives: triflumuron, off-shears backliner, 119 days; and diflubenzuron, long wool jetting on to 7-9 months wool, > 119 days. The model allows for different breakdown rates due to the method of application and length of wool and for changes in the rate of breakdown between application and shearing. It can be used to estimate the expected residue on wool at any time after a specified treatment, provided the amount of chemical applied is known. Conversely, the amount applied can be estimated from the residue and treatment details.

Item Details

Item Type:Refereed Article
Research Division:Agricultural, Veterinary and Food Sciences
Research Group:Animal production
Research Field:Animal protection (incl. pests and pathogens)
Objective Division:Animal Production and Animal Primary Products
Objective Group:Livestock raising
Objective Field:Sheep for wool
UTAS Author:Horton, BJ (Dr Brian Horton)
ID Code:69871
Year Published:1998
Web of Science® Times Cited:11
Deposited By:Agricultural Science
Deposited On:2011-05-23
Last Modified:2011-05-23

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