Essential oils from aromatic plant species and Insecticidal effects on dactylopius opuntiae (Cockerell)(Homoptera: Dactylopiidae)in mobile juveniles

This piece of work was made to characterize physical and chemical properties of essential oils extracted from four aromatic plants species collected in Mexico according to international norms. It was additionally of interest, to determine analytically their compounds and contents. Finally, to study insecticide potential on first instar wild cochineal, an important cactus pest in México. Oils were extracted by means of steam distillation and characterization was made according to international norms AFNOR NA T-101, NA T 75-112 (ISO 280-1976)and NF V 75-113 (ISO 592-1981). Qualitative and quantitative determinations of compounds were made with a Hewlett Packard Gas Chromatograph 5890 Model series II (Palo Alto, Ca.), connected to a Mass Selective Detector Hewlett Packard Model 5972. The insecticide effect was determined by means of bioassay on first instar larvae mobile juveniles and regression parameters calculated using Probit Analysis. Results showed that physical and chemical characteristics of extracted oils fulfill international norms. Most important compounds found in mint: limonene (15 percent), carvone (61 percent), in sweet basil: estragole (20 percent)and linalool (30 percent), in origanum: p-cymeno (21 percent)and carvacrol (43 percent), finally in citronella were found endo-1-bourbonanol (12 percent), citronelol (13 percent), elemol (17 percent)and citronelal (40 percent). The mean lethal concentration (LC 50)of the mint oil in cochineal mobile juveniles was 7,200 ppm, albacar, 21.600, whereas origanum and citronella showed much greater LC 50 values (46.000 and 59.400, respectively). As compared to LC 50 value (1,800 ppm)of tested conventional insecticide mineral oil SAF-T-SIDE (Monterrey-Lawn and Garden Products Inc)mint LC 50 value showed Relative Insecticidal Effect = 4X which means less insecticide effect than the conventional insecticide. This result suggests mint essential oil as a prospect to be used as a natural control agent for this cactus pest.