The cultivation of garlic Allium sativum (Liliales: Liliaceae), a vegetable of great economic importance in Mexico, with a production of 5 901 484 tons in 2013, produced mainly in the States of Zacatecas, Guanajuato, Sonora, Baja California, and Aguascalientes (SAGARPA-SIAP, 2014). In this crop pest problems are rare, but must be addressed promptly to prevent reductions in quality and quantity of garlic harvested within the pests associated with this crop highlights the nematode Ditylenchus dipsaci (Tylenchida: Anguinidae), species more common and economically important in agriculture for the damages and losses caused (^{Cepeda, 1996}; ^{Doucet and De Doucet, 1997}).

The nematode D. dipsaci is one of the plant parasites most devastating and widely distributed, especially in temperate areas; so, it is of great economic importance worldwide and is on the list of quarantined agencies in many countries (^{APPS, 2011}; ^{SENASICA, 2013}), in the case of Mexico the highest incidence of this nematode is in the main producing regions of garlic and onion in the States of Guanajuato, Aguascalientes, Puebla and Veracruz (^{SENASICA, 2013}).

The ecto and endoparasites migratory habits and of this nematode increase its range of host plants, attacking aerial parts, bulbs and tubers of plants (^{Greco et al., 1991}) 450-500 known hosts, finding important species such as garlic, onion, carrots, beans, oats, barley, rye, corn, wheat, potatoes, strawberries, beets, gladiolas, and pines, where Dendroctonus sp., is found, among others (^{Cepeda, 1996}; ^{Bohm and Apablaza, 2005}; ^{SENASICA, 2013}).

This organism feeds on the parenchymal tissue in the stems and bulbs, injecting tissue enzymes that dissolve the middle lamella of the parenchymal tissues causing deformation of the bulb, distortion of stems, petioles, leaves and seeds and strain in leaf tissues that form small and large cavities filled with nematodes, causing rickets with large starches losses among other compounds (^{Potter and Olthof, 1993}; ^{Cepeda, 1996}; ^{Perry and Wright, 1998}). Damage caused by the nematode in growing and increasing the area of spread this pathogen have become a serious problem in areas where garlic is grown mainly in the use of infested seed (teeth/bulbils), it definitely plays an important role in the spread of the nematode. As well as the ability of this organism to enter anhydrobiosis, allowing it to survive under adverse conditions of moisture and remain viable for many years in infested seeds and plant residues (^{Guerrero, 2011}; ^{SENASICA, 2013}).

The populations of D. dipsaci are of great importance to initiate preventive measures. Estimated 20 nematodes per 100 grams of soil can cause considerable damage to plants. All the garlic varieties cultivated in Mexico are susceptible to this pathogen, therefore, in order to control it, is by using problem-free seed or seed treatment and nematicide applications to the infested soil (^{Guerrero, 2011}).

The action of more used to control it, is the application of chemical nematicides; however, cost, residual and phytotoxicity of nematicides for cultivation, limit its application, so it is imperative to seek alternatives to combat pathogenic nematodes, which significantly affect production. At this biocontrol microorganisms from plant extracts and are presented as a promising alternative, which are formulated commercial nematicides from microorganisms, plants and other components having the ability to regulate nematode populations.

An example of this are the Nematrol PLUS; organic nematicide composed of chitosan (Poly-D-glucosamine) and compared with BIOXER 1000; organic soil disinfectant, based on various organic components such as enzymes of Larrea tridentata, ferments of apple, ferment of Lactobacillus, seaweed, aqueous extracts of neem and chrysanthemum. Therefore, the objective of this research was to evaluate the nematicidal activity of two organic products on the nematode D. dipsaci, under laboratory conditions.

The investigation began in February-March 2014 at the Agricultural Experimental field “El Bajio” at the UniversidadAutonomaAgrariaAntonioNarro(UAAAN)in a crop of garlic, var. Tacuascaro, already established; where sampling conducted as directed toward garlic plants, plants in patches of nematode attack symptoms (size reduction, starting at the base yellowing plant tissue and detachment very small bulb and root system). 25 sub-samples of soil collected systematically in a profile of 0-30 cm, which were mixed to obtain a homogeneous mixture (4 kg) and transferred to laboratory Nematology for nematodes by the method of Baermann funnel (^{Cepeda, 1995}). After 24 h of being placed, Baermann funnel proceeded to perform a count of the initial nematode population and immediately returned to the Baermann funnel. Then treatments evaluated directly in the funnel were placed. Five treatments completely randomized design with four replications were established in total, being as follows:

Table 1 Treatment for evaluation to control the stem and bulb nematode Ditylenchus dipsaci. 

*400 L agua, recomendación de campo; ** 200 mL agua, base tratamiento en laboratorio; & Nematrol PLUS; ç BIOXER1 000.

Mortality assessment was carried out 24 h following the application of treatments, for which the final count was performed (counting the living) and was obtained by the difference between the initial-population and final-population and, analysed using an ANOVA with Tukey's mean separation (α= 0.05) using the software SAS 9.0 (^{SAS Institute, 2002}).

In the Table 2, the population is presented at the beginning of the investigation and the final population found 24 after application of treatments to control D. dipsaci, obtained in soil from a crop of garlic with damaging symptoms. In this we can see a significant reduction in the nematode population, due to the application of the treatments, while in the control treatment, the population remained quite similar, with a reduction in the range of 1.0-3.75% mortality.

Table 2 Initial-population and final-population of the bulb nematode Ditylenchus dipsaci in each treatment and replication under laboratory conditions. 

Rep.= repeticiones.

The Table 3 shows the mortality of D. dipsaci, in which the nematicidal activity of the commercial products is seen at different doses; it is observed that chitosan-based products and organic components have an efficient control of the nematode population.

Table 3 Mortality of Ditylenchus dipsaci to the application of chitosan and organic compounds under laboratory conditions. 

Medias con la misma letra, no son significativamente diferentes (Tukey α= 0.05).

Within the test treatments (1-4), for controlling D. dipsaci, no significant differences were found, with a control fluctuating between 86.8 and 97.5%, and for the control, we found a significantly lower mortality, with a median survival of 97.6% (Table 3). Of these treatments, a better control was observed with the chitosan at a dose of 2 mL (4 L ha^-1) to 97.5% and, the product based on organic compounds at a dose of 10 mL (20 L ha^-1) with an averaging 97.3% (gl= 7.19; F= 162.06; p< 0.0001).

In the literature is not mentioned the effect of this product based on chitosan for controlling D. dipsaci (^{SENASICA, 2013}); besides that this product is not indicated for the management of this organism, which provides a new option to control this nematode quite effectively, just as the product based on organic components; although, this is registered for preventing damage caused by this nematode, which in this study is corroborated.