UTILIZAÇÃO DE NEMATICIDAS BIOLÓGICOS PARA O CONTROLE DE NEMATOIDE DE GALHAS NA CULTURA DA ALFACE

Abstract

Lettuce stands out as the most present leafy vegetable in the Brazilian diet. Among the main factors affecting the productivity of lettuce, the gall nematodes deserve special attention. The species Meloidogyne incognita is the most common in tropical growing conditions, in which its parasitism reduces the uptake of water and nutrients and compromises physiological processes of the culture. This condition results in lower lettuce development, making the quality of the product unfeasible. In this sense this work aimed to evaluate the influence of biological nematicides in the control of M. incognita in lettuce culture, and its interference in plant development. In chapter I, in the greenhouse, lettuce seeds cultivar Blue seeds BS AC0063 were treated with the following biologicals and their respective concentrations: T1: Bacillus methylotrophicus at 2.5 - 3.0 - 3.5 - 4.0 - 4.5 mL kg-1 of seed; T2: B. subtilis at 1.5 - 2.0 - 2.5 - 3.0 - 3.5 ml kg -1 of seed; T3: B. amyloliquefaciens at 3 - 3.5 - 4.0 - 4.5 - 5.0 g kg -1 of seed; T4: Trichoderma harzianum 3 - 3.5 - 4.0 - 4.5 - 5.0 g kg -1 of seed; T5: T. asperellum at 5 - 5.5 - 6.0 - 6.5 - 7.0 mL kg-1 of seed, and control. Then they were sown in trays and after 16 days were transplanted into 3 L pots containing soil + sand + substrate in the ratio of 2:1:1, previously autoclaved (120 ºC, 2 h). A 5X5 (5 biological products x 5 concentrations) completely randomized design with six repetitions was used. On the 3rd day after transplanting, 5,000 M. incognita eggs per plant were inoculated. In chapter II, in beds where the presence of M. incognita had been previously detected, the initial population was quantified, and subsequently seed treatment was performed with the isolates and initial concentrations used in chapter I. A randomized block design was used, 4 blocks, 6 plots per block, with an experimental unit of 8 plants, removing 4 to be submitted to the evaluations. On the 55th day after inoculation, the following variables were evaluated: aboveground fresh mass (MFPA), root fresh mass (MFR), root length (C.R), stem diameter (D.C) and reproduction factor (FR). In the greenhouse test, the isolates B. methylotrophicus at concentration 2.5 mL kg-1 improved the vegetative development of lettuce, 58.90 and 60.25%, MFPA and C.R, respectively, and at concentration 4.0 mL kg-1 provided MFR of 44.82% higher than the other isolates. B. subtilis at concentrations 3.0, 1.5 and 2.5 mL kg-1 showed addition in MFPA, D.C and C.R of 60.54, 165.90 and 68.65% respectively. B. methylotrophicus at concentration 4.5 mL kg-1 and B. subtilis at concentration 1.5 mL kg-1, reduced M. incognita reproduction by 48.44 and 53.98%, respectively. In chapter II, T. harzianum promoted increment in MFPA by 25.14%, D.C by 195.18%, C.R by 58.91%, root fresh mass -21.14%, relative to control. B. amyloliquefaciens increased MFPA by 25.09%, D.C by 144.57%, C.R by 74.25%, MFR by -7.22%. There was a reduction in the FR of M. incognita in treatments with isolates B. amyloliquefaciens and T. harzianum by 37.60% and 28.86%, respectively. Based on the results, it was concluded that B. methylotrophicus, B. subtilis, B. amyloliquefaciens and T. harzianum enhance the vegetative development of lettuce crop. B. methylotrophicus and B. subtilis at respective concentrations 4.5 mL kg-1 1.5 mL kg-1, enable reduction in M. incognita population in lettuce under protected cultivation conditions. B. amyloliquefaciens and T. harzianum provided the greatest reduction in the reproduction of M. incognita under field culture system.