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The vertical migration of second-stage juveniles (J2) of Meloidogyne floridensis and M. incognita was investigated in segmented 14-cm long PVC soil columns having their top ring in contact with soil of a potted plant. Both bottom and top rings were screened appropriately to allow only upward nematode movement and preventing root penetration from the potted plant into the soil in the column. Plants used for nematode’s stimuli were the nematode attractive tomato (Solanum lycopersicum L.) ‘Cobra’ and the nematode repellent French marigold (Tagetes patula L.) var. Petite. Host-free columns were used as control. Columns with and without plants were placed in growth chambers at 20 °C and inoculated with each root-knot nematode species by injecting 1000 J2 through a hole in the basal ring of each column. Columns were dismantled at 3, 6 and 9 days after injection and J2 were extracted from soil of each ring and the planted pot; additionally, roots in the top pot were stained to observe J2 penetration. No preferential upward migration towards either plant stimuli was observed, but M. floridensis was more migrant than M. incognita, with 4.4% and 1.6% of active J2, respectively, reaching an upward distance of more than 13 cm regardless of plant stimuli. This study supports random migration of root-knot nematode J2, even without stimulus from a host plant.

Root-knot nematodes (Meloidogyne spp.) can parasitize and reduce yields of nearly all agricultural crops. Although migration studies focus on the model species, M. incognita, there is little information about M. enterolobii, which has been a major threat for guava in Brazil. The vertical migration of second-stage juveniles (J2) of M. enterolobii and M. incognita was evaluated to determine the effect of good host and nonhost plants on nematode motility. Fourteen-cm long soil columns were constructed of PCV rings with Styrofoam cups containing a 4-week-old tomato or marigold (Tagetes patula) seedlings as plant stimuli; host-free cups were used as nontreated control. After inoculating 1000 freshly-hatched J2, the columns were placed in environmental chamber sets at 20 °C. The columns were disassembled at 3, 6, and 9 days after inoculation (DAI). The experiment was completely randomized block with four replicates. J2 were extracted from each ring and cup, while tomato and marigold roots were stained to observe J2 that penetrated roots. Data were subjected to repeated-measure MANOVA and chi-square test to compare J2 distribution along the columns. The migrations under tomato and marigold stimuli were comparable to those under host-free columns. Although both species migrated over 13 cm, M. enterolobii was more mobile than M. incognita. Juveniles of M. enterolobii infected tomato roots as early as 3 DAI, whereas marigold delayed nematode penetration. Our results show that two species of root-knot nematodes behave differently within the soil, and under the same conditions J2 of M. enterolobii migrate faster than M. incognita.

Dois experimentos foram realizados no Município de Camutanga, Pernambuco, objetivando avaliar relações entre a distribuição espaço-temporal dos nematoides endoparasitas Meloidogyne e Pratylenchus e atributos biométricos, nutricionais e enzimáticos da cana-de-açúcar (cana-planta e cana-soca). As avaliações, realizadas aos 6, 9 e 12 meses após o plantio da cana (Área 1) e corte para renovação da soca (Área 2), fundamentaram-se na densidade populacional dos endoparasitas na raiz, altura, diâmetro e número de colmos da cana, teores de fósforo, potássio, cálcio e magnésio na folha e atividade das enzimas ascorbato peroxidase e superóxido dismutase. Os dados foram submetidos à análise descritiva e geoestatística, gerando mapas de isolinhas por meio de semivariograms teóricos ajustados às semivariâncias dos dados. Os modelos esférico e exponencial foram ajustados à maioria das variáveis avaliadas. Na área 1, os padrões de distribuição espaço-temporal de Meloidogyne e Pratylenchus diferiram ao longo do tempo, tornando-se, no geral, mais homogêneos. O desenvolvimento da cana-soca na área 2 foi prejudicado por regiões de alta densidade populacional de Pratylenchus, as quais coincidiram com regiões de baixos teores de potássio e magnésio.

The peach root-knot nematode, Meloidogyne floridensis, is an emerging species and may become a threat to peach growers if contamination and spread are not avoided. The influence of temperature and two plants – tomato (Solanum lycopersicum) and French marigold (Tagete patula) – on the vertical migration of second-stage juveniles (J2) of M. floridensis was studied using 14-cm long segmented soil columns. Plants were transplanted into cups attached to the top of each column. Nylon meshes were placed between cups and columns to prevent downward root growth. About 1,000 freshly hatched J2 were injected into the base of the columns and then the columns were transferred to growth chambers at 20 and 26°C under a completely randomized block design with four replicates. The number of J2 in each ring of the columns as well as inside tomato or marigold roots was recorded at 3, 6, 9, and 12 days after injection (DAI). Nematode data were subjected to a repeated measures MANOVA. The presence of plants did not improve J2 migration as compared to control. M. floridensis migration was best at 20°C at first, with J2 migrating more than 13 cm as soon as 3 DAI, while it took 9 DAI for J2 to migrate long distances at 26°C. The distribution of J2 along the columns was similar at both temperatures at 12 DAI. Temperature had no influence on J2 penetration. French marigold did not hinder J2 migration, but fewer J2 penetrated its roots.

Edaphic climatic conditions directly affect the population dynamics of nematode assemblages and management strategies. The objective of this study was to characterize spatiotemporal changes in nematode abundance and diversity in sugarcane fields of northeastern Brazil under different edaphic climatic conditions. Soil samples from seven geoenvironmental sites under continuous cultivation were taken at planting and 4, 9, and 14 months after planting. Nematode abundance and diversity varied with the soil’s physical and chemical characteristics. Sites in the rainfed and irrigated coastal tables as well the floodplain had higher number of nematodes in contrast to the flat-land and hillside. The abundance of plant-parasitic nematodes increased concurrently with crop development, but the number of taxa decreased. Meloidogyne and Pratylenchus were the dominant plant-parasitic genera across locations, but bacterivores were dominant in southern sites at field replanting. Heat map delineated two distinct groups of nematode distribution within the geoenvironmental zones, rather than the sampling times. Pratylenchus density was high in both groups, but in contrast with Meloidogyne and Criconemella, the abundance of Pratylenchus and Helicotylenchus was higher in sites with lower soil bulk density and higher porosity, clay, organic matter, and water contents as those in the southern sites, reflecting edaphic climatic conditions.

Considering the relevant importance of guava (Psidium guajava) in Northeastern Brazil along with the benefits of neem cake amendments on soil characteristics, this work evaluated the effects of neem cake on chemical attributes of a Regosol under irrigated guava orchard in an alluvial valley of Pernambuco semi-arid region. Evaluations were carried out in two areas (area 1 - with neem cake; area 2 - without neem cake) at three periods: before the first application of neem cake, 90 days after the first application and 90 days after the second application. A regular 8 × 6-point grid was designed in each area and the soil was sampled for total organic carbon, pH, soluble salts (Na+, K+, Ca2+ and Mg2+) and total nitrogen contents, as well as soil C-CO2 evolution rate in soil. Geostatistical analysis pointed out the spherical model as the best fit to the studied variables, followed by the Gaussian model, with ranges from 12 to 60.5 m. Neem cake incorporation increased spatial variability and the contents of the evaluated soil chemical attributes. RESUMO Considerando a importância do cultivo de goiabeiras (Psidium guajava) para o nordeste do Brasil e os benefícios da aplicação da torta de nim nas características do solo, avaliou-se o efeito da aplicação de torta de nim nos atributos químicos de um Neossolo Regolítico cultivado com goiabeiras irrigadas no semiárido de Pernambuco. Para as avaliações foram usadas duas áreas (área 1 - com nim; área 2 - sem nim) e três períodos, antes da aplicação do nim, 90 dias após a primeira aplicação e 90 dias após a segunda aplicação; assim, 96 amostras de solo foram coletadas em duas malhas regulares de 8 × 6 pontos amostrais e realizadas análises do teor de carbono orgânico total, pH, teores de sais solúveis (Na+, K+, Ca2+e Mg2+), nitrogênio total e taxa de evolução C-CO2 do solo. O modelo esférico foi o que melhor se ajustou às variáveis estudadas seguido pelo gaussiano, com alcances que variaram de 12 a 60,5 m. A incorporação da torta de nim aumentou a variabilidade espacial e a oferta dos atributos de solo estudados.