ABSTRACT
Comparison and Characterization of Garlic (Allium sativum L.) Bulbs Extracts and Their Effect on Mortality and Repellency of Tetranychus urticae Koch (Acari: Tetranychidae)

Carlos Augusto Hincapié Ll.1, Gloria Eugenia López P.1 y Ricardo Torres Ch.2
 

Tetranychus urticae Koch is a pest that causes great economic losses because it attacks a wide range of host plants. Also, some populations have developed resistance against commercial acaricides. This work compares different extracts from garlic (Allium sativum L.) bulbs measuring their toxicity and repellency effects on T. urticae. Extracts were obtained using as solvents CO2 in supercritical conditions (CSC), ethanol and petroleum ether using soxhlet and soaking methods and soaking in water. The supercritical fluid extraction technique allows for obtaining extracts at low temperature using high pressures, avoiding compound degradation and making possible solvent separation by exposing the extract at room temperature. Mites were bred on bean plants (Phaseolus vulgaris L.) in a laboratory environment in Laureles Campus, Universidad Pontificia Bolivariana, Medellín, Colombia. Mortality was evaluated putting 10 mites in P. vulgaris 3 cm diameter leaf discs previously submersed in the extract. The lowest mean lethal concentrations (LC50) were obtained with the CSC method (8.1188, 5.4105, 2.8206 mg g-1 at 24, 48 and 72 h, respectively). Extracts were characterized using gas chromatography/mass spectrometry (GC/MS), finding vinyl dithiins (63.11%), diallyl disulfide (10.88%) and diallyl trisulfide (10.4%) as the main compounds in the CSC extract. The main conclusion is that, in comparison with other techniques of extraction from garlic bulbs used in this study, supercritical fluids allow for obtaining extracts with a higher concentration of biologically active compounds against T. urticae.

Keywords: two-spotted spider mite, plant extracts, miticidal effect, Liliaceae.
1 Universidad Pontificia Bolivariana, Facultad de Ingeniería Agroindustrial, Grupo de Investigaciones Agroindustriales (GRAIN), A.A. 56006, Medellín, Colombia. E-mail: carlos.hincapie@upb.edu.co *Corresponding author.
2 Universidad Nacional de Colombia, Magíster en Ciencias Químicas, Calle 59A No 63-20 Medellín, Colombia. E-mail: rtorres@epm.net.co.
The summary of this work was presented at the 33rd Congress of the Colombian Entomology Society (SOCOLEN) in Manizales, Colombia on July 28, 2006.