Garlic essential oil reduces the population of Meloidogyne incognita in tomato plants

The root-knot nematode Meloidogyne incognita causes losses in tomato production, making new methods/products to control this parasite desirable. Garlic essential oil (GEO) is potentially useful for controlling M. incognita. Here, GEO was obtained by hydrodistillation, dissolved in water and used against M. incognita in vitro. At 63 μg mL−1, this oil was more active against M. incognita eggs and second-stage juveniles (J2) than the nematicide Carbofuran at 173 μg mL−1. The main components of the oil, according to gas chromatography-mass spectrometry analysis, are diallyl trisulphide (66.7%) and diallyl disulphide (21.3%), which presented lethal concentrations to 50% (LC50) J2 equal to 36.2 ± 1.7 and 134.4 ± 19.4 μg mL−1, respectively, while the LC50 for Carbofuran was 151.6 ± 2.1 μg mL−1. When the J2 submerged in a solution of the oil at 250 μg mL−1 were used to infest tomato plants, the number of galls and eggs of M. incognita in the roots were reduced to values statistically equal to those obtained when J2 were submerged in a solution of Carbofuran at 415 μg mL−1. The vapour of the oil was also as active in vitro against M. incognita eggs and J2 as the fumigant nematicide Dazomet. The infectivity and reproduction of M. incognita in tomato plants cultivated in substrate inoculated with eggs of the nematode and treated with 0.2 mL of oil per L of substrate were statistically equal to those observed when the oil was replaced by 0.25 g of Dazomet per L of substrate. These findings confirm the activity of GEO and its components against M. incognita, suggesting its potential as a new fumigant nematicide to control the nematode in tomato plants.