Banca de DEFESA: ALESSANDRA PAIVA RIBEIRO

Management Strategies Aiming at the Control of Phytonematodes in Lettuce in Cultivation under 

Agroecological  Transition: Green Manure, Genetic Resistance, Organic Fertilization

Olericulture; Lactuca sativa; Meloidogyne javanica.

This study was conducted in Rosário da Limeira, Minas Gerais, Brazil, on a rural property with a history of losses caused by root-knot nematodes (Meloidogyne spp.). Based on the premise that soil and crop management strategies can reduce losses caused by this disease, the present work was developed with the following objectives: a) To compare different lettuce crop management methods aiming to reduce losses caused by phytoparasitic nematodes and assessing their impact on yield; b) To investigate and evaluate the influence of green manure management with Crotalaria juncea as a pre-planting strategy for controlling nematodes in lettuce cultivation; c) To evaluate the performance of the cultivar BRS Leila, resistant to root-knot nematodes, in the region; d) To develop a booklet with management practices and techniques for nematode control, specifically aimed at organic and agroecological farmers, providing practical and applicable information. To this end, two trials were conducted: the first from November 2023 to April 2024, and the second between September and November 2024. Initially, an area with recurring losses due to root-knot nematodes in lettuce was selected. Subsequently, a soil chemical analysis and nematode identification were performed, confirming the presence of Meloidogyne javanica. Upon detecting soil acidity, liming was recommended, followed by soil preparation and the planting of Crotalaria juncea in 50% of the plots. The Crotalaria was cut at 122 days after sowing, at the flowering stage, and the straw was distributed over the beds. Five days later, lettuce seedlings of the Vanda cultivar were transplanted. Harvesting was carried out 44 days after transplanting, and total biomass and the number of root galls were evaluated. In the second trial, the effect of fertilization with organic compost based on poultry litter (CAV) and biochar (FC) was assessed, using the following proportions of CAV:FC – 100:0, 95:5, 90:10, and 85:15 – and two lettuce cultivars (Vanda and BRS Leila). The seedlings were transplanted and grown under micro-sprinkler irrigation, with harvesting also carried out 44 days after transplanting. The variables evaluated included fresh shoot and root mass, and head diameter. The Crotalaria pre-cultivation reduced nematode incidence and significantly increased lettuce productivity, with an average of 107.64 g of fresh mass, compared to 62.27 g in the plots without Crotalaria. The addition of biochar in varying concentrations favored fresh biomass accumulation, although without significant differences among treatments. No significant differences were observed between the cultivars.