Effectiveness and chemical composition of plant based acaricides against the two spotted spider mite Tteranychus urticae Koch (Acari : Tetranychidae)
(2012)
Files
thesesabrinecorrectionfinale12avrilfinaleversion.pdf
Restricted Access - Adobe PDF
- 3.76 MB
Details
- Authors
- Supervisors
- Abstract
- (en) Since 20 years, the development of integrated pest management (IPM) strategies is increasing since many problems appeared with the use of synthetic pesticides. Plant extracts are more and more considered within IPM strategies as alternative or complementary approach to insecticide treatments. Many plant essential oils show a broad spectrum of activity against pests. In this PhD thesis, I investigated the acaricidal effects of four plant extracts: Deverra scoparia Coss & Durieu (Araliales: Apiaceae), Santolina africana Jord & Fourr (Asterales: Asteraceae), Hertia cheirifolia Kuntze (Asterales: Asteraceae) and Allium sativum Linn. (Asparagales: Alliaceae) collected from Tunisia on the mite Tetranychus urticae Koch (Acari: Tetranychidae), one of the most serious phytophagous pests in the world. In the first step, the mortality and fecundity of female mites were measured upon treatment with an increase of the concentrations of essential oils with a potter spray tower. Mite mortality increased with oil concentration, with LC50 values ranging from 1.8 to 7.5 mg/l for all extracts. A reduction of the fecundity was already observed at lower concentrations ranging from 0.07 to 0.74 mg/l for all extracts. For a comprehensive evaluation of the potential of these four plant extracts as acaricides, they were characterized by GC, GC/MS and HPLC in order to analyse their chemical composition. Afterwards, I evaluated the acaricidal properties of the major components to identify the compounds conferring the biological activities against T. urticae. In a next step, artificial blends of components of the three essential oils were also prepared and tested with individual components missing from the mixture. The results showed that the presence of all constituents was necessary to equal the toxicity of the three natural oils. I analysed the persistence of acaricidal activity of these four extracts. Results showed that S. africana oil is the most persistent extract; D. scoparia oil is the less persistent. The combination of essential oils with a non-ionic surfactant (Tween 20), which is known as a binder, significantly increased the persistence of the biological activity of all extracts that lasts 10 days. Moreover, the combination with Tween increased significantly the differences between the plant extracts. Finally, I analyzed the resistance developped by the use of these 4 natural extracts. The treatment of S. africana did not induce any resistance while a low development of resistance was observed with H. cheirifolia, A. sativum and D. scoparia. In conclusion, compared to synthetic acaricides, the efficacy of these extracts against the two spotted spider mite is significantly higher with lower LC50 values, and higher decrease of the fertility. Moreover, the possibility to control the persistence and the slow development of resistance make them promising for pest management.
- Affiliations
Citations
Attia, S. (2012). Effectiveness and chemical composition of plant based acaricides against the two spotted spider mite Tteranychus urticae Koch (Acari : Tetranychidae). https://hdl.handle.net/2078.5/69510