The fluctuations in Meloidogyne densities and fungal egg parasitism were determined from February 2015 to July 2016 in four vegetable production sites conducted under organic production and two sides conducted under integrated standards. At each site, the soil nematode densities at transplanting and at the end of the crops, the galling index, the number of eggs in roots, and the percentage of fungal egg parasitism were determined, and the fungal species were identified. In addition, two pot experiments were conducted with soil taken from each site in February 2015 and 2016 to assess the fungal egg parasitism comparing non-sterile and sterile soil from each site. In field conditions, the nematode population densities in the soil decreased along the crop rotations. The maximum number of eggs per plant was recorded in the spring–summer crops. Egg parasitism ranged from 11.2 to 55% in the organic sites and from 0.8 to 16.5% in the integrated production sites. Pochonia chlamydosporia was the only fungal species isolated in five of the six sites. In both pot experiments, the number of eggs per plant was lower in non-sterile than in sterile soils, except for the M10.45 site, where fungal egg parasites were not recovered. P. chlamydosporia was the only fungal species isolated, ranging between 11 and 74%. Therefore, P. chlamidosporia was the most prevalent fungal species related to Meloidogyne suppression.

The effect of molasses alone or combined with Trichoderma asperellum T34 Biocontrol^® was assessed on Meloidogyne reproduction, disease severity, and density and activity of soil microorganisms in pot and field experiments. Firstly, molasses application at 1 mL m⁻² was assessed in four different textured soils. Secondly, molasses application at 5, 10, 20, and 40 mL m⁻², alone or combined with T34, was assessed in pot and field experiments at 10 mL m⁻² in two different textured soils. The application of 1 mL m⁻² of molasses was effective in reducing nematode reproduction in the loam textured soil but not in sandy clay loam, sandy loam, or clay loam textured soils. Increasing molasses dosage reduced the tomato dry shoot and fresh root weights, producing phytotoxicity at 40 mL m⁻². The disease severity and nematode reproduction were reduced between 23% and 65% and 49% and 99%, respectively. In the field experiment, molasses applied at 10 mL m⁻² reduced the disease severity and the nematode reproduction in the loam textured soil. The soil microbial density and activity did not increase in sites where the nematode reproduction and the disease severity were reduced by molasses application, irrespective of T34.

Meloidogyne spp. are an important threat to horticulture and cause substantial yield losses. Plant resistance is an alternative control method for chemical nematicides. This study highlights the host suitability of the lettuces cultivars Grand Rapids and Salinas 88 and the beans cultivars Aporé, Cornell 49242, Macarrão Atibaia and Ouro Negro to four Meloidogyne incognita and seven M. javanica isolates from Spain in a pot experiment. Moreover, the response of these cultivars to increasing M. incognita densities (Pi) was assessed in a plastic greenhouse. The lettuce cultivar Regina 71 and the bean cultivar Bolinha were included as susceptible standards for comparison. It was found that Grand Rapids and Salinas 88 lettuces were resistant to the most nematode isolates in the pot experiment but were classified as slightly and moderately resistant, respectively, in the plastic greenhouse at increasing Pi. Regarding the beans, Aporé was resistant to the majority of the Meloidogyne isolates whereas Macarrão Atibaia and Ouro Negro were slightly resistant and Cornell 49242 was susceptible in the pot experiment. In the plastic greenhouse, Aporé was the only cultivar able to effectively suppress the nematode reproduction irrespective of Pi, while Ouro Negro became less resistant as Pi increased. These results play an important role in enhancing the effective and ecofriendly Meloidogyne management strategies.