South African plantation forest nursery pesticide -use: current status, pesticide identification for management, and screening of fungicides for pathogen control
- Authors: Opperman, Ilke
- Date: 2023-04
- Subjects: Forest insects –Control – South Africa , Pesticides -- Environmental aspects , Pest management
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61370 , vital:70618
- Description: Forest nurseries are exposed to many challenges during the production of plant material, with pests and pathogens two of the most important. Management of pests and diseases require the use of multiple methods, including cultural, biological, and chemical control strategies in an integrated nursery pest management plan (IPM). In most nurseries, where hygiene practices and biological controls do not prevent the presence of pests and pathogens, they are managed through the use of pesticides. Forestry companies are regulated by both Government and Forestry Certification bodies. These include South African legislation pertaining to pesticides regulated by the Registrar Act 36 of 1947, the Forest Stewardship Council (FSC) and the Programme for the Endorsement of Forest Certification (PEFC). A limited number of pesticides, with an even more limited range of active ingredients, and not targeting all known plantation forestry pests/pathogens, are currently registered for use against pests and pathogens in plantation forestry in South Africa. Many of these have been in use for more than a decade, posing a serious risk in terms of resistance build-up. There is a major need for the identification and testing of additional/alternative products (biological natural or synthetic) for use against the range of pests and pathogens that occur on the various plantation tree species and hybrid combinations that are raised in nurseries. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science & Management, 2023
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- Date Issued: 2023-04
Voltammetric analysis of pesticides and their degradation: A case study of Amitraz and its degradants
- Authors: Brimecombe, Rory Dennis
- Date: 2006
- Subjects: Hydrolysis , Biodegradation , Voltammetry , Pesticides -- Biodegradation , Pesticides -- Environmental aspects , Acaricides , Acaricides -- Physiological effect
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4131 , http://hdl.handle.net/10962/d1015724
- Description: Amitraz is a formamide acaricide used predominantly in the control of ectoparasites in livestock and honeybees. Amitraz hydrolysis is rapid and occurs under acidic conditions, exposure to sunlight and biodegradation by microorganisms. The main hydrolysis product of amitraz, 2,4-dimethylaniline, is recalcitrant in the environment and toxic to humans. An electrochemical method for the determination of total amitraz residues and its final breakdown product, 2,4-dimethylaniline, in spent cattle dip, is presented. Cyclic voltammetry at a glassy carbon electrode showed the irreversible oxidation of amitraz and 2,4-dimethylaniline. A limit of detection in the range of 8.5 x 10⁻⁸ M for amitraz and 2 x 10⁻⁸ M for 2,4-dimethylaniline was determined using differential pulse voltammetry. Feasibility studies in which the effect of supporting electrolyte type and pH had on electroanalysis of amitraz and its degradants, showed that pH affects current response as well as the potential at which amitraz and its degradants are oxidised. Britton-Robinson buffer was found to be the most suitable supporting electrolyte for detection of amitraz and its degradants in terms of sensitivity and reproducibility. Studies performed using environmental samples showed that the sensitivity and reproducibility of amitraz and 2,4-dimethylaniline analyses in spent cattle dip were comparable to analyses of amitraz and 2,4-dimethylaniline performed in Britton-Robinson buffer. In addition, the feasibility qf measuring amitraz and 2,4-dimethylaniline in environmental samples was assessed and compared to amitraz and 2,4-dimethylaniline analyses in Britton-Robinson buffer. Amitraz and 2,4-dimethylaniline were readily detectable in milk and honey. Furthermore, it was elucidated that 2,4-dimethylaniline can be metabolised to 3-methylcatechol by Pseudomonas species and the proposed breakdown pathway is presented. The biological degradation of amitraz and subsequent formation of 2,4-dimethylaniline was readily monitored in spent cattle dip. The breakdown of amitraz to 2,4-dimethylaniline and then to 3-MC was monitored using cyclic voltammetry.
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- Date Issued: 2006