Comparación y caracterización de extractos de bulbos de ajo (Allium sativum L.) y su efecto en la mortalidad y repelencia de Tetranychus urticae Koch (Acari: Tetranychidae)

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 (8118.8, 5410.5, 2820.6 mg kg^-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.