Influência das propriedades do solo na incidência do cancro do eucalipto.

Resumo apresentado no Congresso Brasileiro de Fitopatologia, 30., 1997, Poços de Caldas

Levantamento de Valsa ceratosperma e de Cryphonectria cubensis em cancros de Eucalyptus grandis em três locais do Estado de São Paulo.

A incidência de cancros e dos fungos associados foi avaliada em talhões de Eucalyptus grandis, com idades variando entre 3 e 4 anos, em Altinópolis, Luiz Antônio e Moji Guaçu, Estado de São Paulo. Comparando-se Altinópolis e Luiz Antônio, houve maior incidência de cancros basais no primeiro local e de cancros não basais no outro. Em Altinópolis, Cryphonectria cubensis predominou nos cancros basais e Valsa ceratosperma nos não basais. Em Luiz Antônio, V. ceratosperma predominou sobre C. cubensis, principalmente nos cancros não basais. Comparando-se Altinópolis e Moji Guaçu, houve incidência de cancro significativamente superior e similaridade no número total de cancros , no primeiro local. Em Moji Guaçu, cancros basais e C. cubensis foram predominantes. De um modo geral, a associação de C. cubensis foi maior com cancros basais e de V. ceratosperma com cancros não basais. Considerações são feitas sobre a variação da incidência da doença nos locais estudados

Surto epidêmico da mancha foliar causada por Cylindrocladium spp e sua relação com o crescimento de espécies/procedências de Eucalyptus na região de Tucurui, PA.

Plantios experimentais com 15-18 meses de idade de diferentes especies/procedencias de Eucalyptus implantados na regiao de Tucurui,PA, foram atingidos por um surto epidemico de uma mancha foliar associada a varias especies de Cylindrocladium, no periodo chuvoso de 1988. Avaliacao da doenca no campo revelou grande variacao de resistencia entre especies/procedencias testadas. Algumas que apresentaram de moderado a intenso desfolhamento,como E.citriodora Anhembi e E.tereticornis Anhembi, tiveram a sua taxa de crescimento reduzida e um aumento de falhas associado a doenca. Outras especies/procedencias, como E.urophylla Anhembi (Flores) e E.terelliana Anhembi, com pouca ou nenhuma doenca, tiveram,ao contrario, a sua taxa de crescimento mantida ou ate acelerada no periodo de ocorrencia da epidemia. Com a diminuicao das chuvas, as especies/procedencias mais afetadas mostraram, no entanto, recuperacao na sua taxa de crescimento

Mating vibrational signal transmission through and between plants of an agricultural pest, the Glassy-Winged Sharpshooter

The agricultural pest, glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, relies primarily on successful vibrational communication across its home plant. Males and females engage in a vibrational duet to identify correct species, attractiveness of mate, and location on the plant. The signal produced by these animals has a dominant frequency component between 80 and 120 Hz, with harmonics spaced approximately 100 Hz apart. However, our analysis revealed that not all harmonics are present in every recorded signal. Therefore, we sought to understand how the GWSS vibrational communication signal changes over distance on the plant. We have confirmed that first, with increasing distance fewer high frequency harmonics are present. Second, at distances of only 50 cm, there is a difference in the latency of signal arrival based on the frequency, with higher frequencies arriving sooner. Finally, the animal appears to generate no airborne signal component, yet, the low frequencies are clearly detectable in neighboring plants by the signal “jumping” from leaf-to-air-to-leaf. Together, these results highlight the complexity of vibration transmission in plants and the possibility of alteration and disruption of the GWSS signal

Infectivity and Transmission of Xylella fastidiosa by Philaenus spumarius (Hemiptera: Aphrophoridae) in Apulia, Italy

Discovery of Xylella fastidiosa from olive trees with "Olive quick decline syndrome" in October 2013 on the west coast of the Salento Peninsula prompted an immediate search for insect vectors of the bacterium. The dominant xylem-fluid feeding hemipteran collected in olive orchards during a 3-mo survey was the meadow spittlebug, Philaenus spumarius (L.) (Hemiptera: Aphrophoridae). Adult P. spumarius, collected in November 2013 from ground vegetation in X. fastidiosa-infected olive orchards, were 67% (40 out of 60) positive for X. fastidiosa by polymerase chain reaction (PCR) assays. Euscelis lineolatus Brulle were also collected but tested negative for the pathogen. Transmission tests with P. spumarius collected from the Salento area were, therefore, conducted. After a 96-h inoculation access period with 8 to 10 insects per plant and a 30-d incubation period, PCR results showed P. spumarius transmitted X. fastidiosa to two of five periwinkle plants but not to the seven olive plants. Sequences of PCR products from infected periwinkle were identical with those from X. fastidiosa-infected field trees. These data showed P. spumarius as a vector of X. fastidiosa strain infecting olives trees in the Salento Peninsula, Italy

Transmission of the frequency components of the vibrational signal of the glassy-winged sharpshooter, Homalodisca vitripennis, within and between grapevines

The agricultural pest, Homalodisca vitripennis, relies on vibrational communication through plants for species identification, location, and courtship. Their vibrational signal exhibits a dominant frequency between 80 and 120 Hz, with higher frequency, lower intensity harmonics occurring approximately every 100 Hz. However, previous research revealed that not all harmonics are recorded in every signal. Therefore, how the female H. vitripennis vibrational signal changes as it travels through the plant was investigated. Results confirmed that transmission was a bending wave, with decreased signal intensity for increasing distance from the source; moreover, at distances of 50 cm, higher frequencies traveled faster than lower frequencies, suggesting that dispersion of H. vitripennis signal components may enable signaling partners to encode distance. Finally, H. vitripennis generates no detectable airborne signal (pressure wave), yet their low vibrational frequency components are detectable in neighboring plants as a result of leaf-to-air-to-leaf propagation. For instance, with isolated key female signal frequencies, 100 Hz was detected at a 10 cm gap between leaves, whereas 600 Hz was detectable only with a 0.1 cm gap. Together, these results highlight the complexity of vibration propagation in plants and suggest the possibility of the animals using the harmonic content to determine distance to the signaling H. vitripennis source

Update of the Scientific Opinion on the risks to plant health posed by Xylella fastidiosa in the EU territory

EFSA was asked to update the 2015 EFSA risk assessment on Xylella fastidiosa for the territory of the EU. In particular, EFSA was asked to focus on potential establishment, short‐ and long‐range spread, the length of the asymptomatic period, the impact of X. fastidiosa and an update on risk reduction options. EFSA was asked to take into account the different subspecies and Sequence Types of X. fastidiosa. This was attempted throughout the scientific opinion but several issues with data availability meant that this could only be partially achieved. Models for risk of establishment showed most of the EU territory may be potentially suitable for X. fastidiosa although southern EU is most at risk. Differences in estimated areas of potential establishment were evident among X. fastidiosa subspecies, particularly X. fastidiosa subsp. multiplex which demonstrated areas of potential establishment further north in the EU. The model of establishment could be used to develop targeted surveys by Member States. The asymptomatic period of X. fastidiosa varied significantly for different host and pathogen subspecies combinations, for example from a median of approximately 1 month in ornamental plants and up to 10 months in olive, for pauca. This variable and long asymptomatic period is a considerable limitation to successful detection and control, particularly where surveillance is based on visual inspection. Modelling suggested that local eradication (e.g. within orchards) is possible, providing sampling intensity is sufficient for early detection and effective control measures are implemented swiftly (e.g. within 30 days). Modelling of long‐range spread (e.g. regional scale) demonstrated the important role of long‐range dispersal and the need to better understand this. Reducing buffer zone width in both containment and eradication scenarios increased the area infected. Intensive surveillance for early detection, and consequent plant removal, of new outbreaks is crucial for both successful eradication and containment at the regional scale, in addition to effective vector control. The assessment of impacts indicated that almond and Citrus spp. were at lower impact on yield compared to olive. Although the lowest impact was estimated for grapevine, and the highest for olive, this was based on several assumptions including that the assessment considered only Philaenus spumarius as a vector. If other xylem‐feeding insects act as vectors the impact could be different. Since the Scientific Opinion published in 2015, there are still no risk reduction options that can remove the bacterium from the plant in open field conditions. Short‐ and long‐range spread modelling showed that an early detection and rapid application of phytosanitary measures, consisting among others of plant removal and vector control, are essential to prevent further spread of the pathogen to new areas. Further data collection will allow a reduction in uncertainty and facilitate more tailored and effective control given the intraspecific diversity of X. fastidiosa and wide host range