Dispersão anemófila do fungo Lasiodiplodia theobromae em plantações de coqueiro

Abstract

RESUMONeste trabalho determinou-se a dispersão anemófila de conídios de Lasiodiplodia theobromae, agente causal da queima das folhas do coqueiro (Cocos nucifera), e sua relação com a precipitação pluviométrica. Para tanto, cinco armadilhas cata-vento e uma armadilha tipo Burkard, coletoras de esporos, foram instaladas nas entrelinhas de um coqueiral, a 1,80 m de altura do solo. Os conídios foram capturados em fitas transparentes, untadas com solução adesiva de gelvatol e vaselina. Semanalmente, as fitas foram retiradas das armadilhas e remontadas em lâminas para microscopia, onde era contado o número de conídios capturados, com auxilio de um microscópio. Esses dados foram coletados durante um ano e relacionados com dados pluviométricos obtidos na área experimental. Para as armadilhas cata-vento, a maior quantidade de conídios foi de 231 unidades, no mês de outubro. Para a armadilha Burkard, a maior quantidade capturada foi de 3.072 conídios, no mês de junho. Em geral, durante todo o ano, houve predominância na liberação de esporos no período diurno, ocorrendo maior captura entre 6:00 e 10:00 h. O número de conídios capturados pelos dois tipos de armadilhas relacionou-se com a precipitação de forma positiva entre 25 e 80 mm, e após 80 mm, negativamente. Foram estabelecidas curvas de tendências da quantidade de conídios capturados nos dois tipos de armadilhas, em função da pluviosidade mensal, através de equações de regressões cúbicas. As curvas apresentaram formatos semelhantes. A liberação dos conídios foi estimulada sempre que a pluviosidade mensal atingia o mínimo de 25 mm. O ponto de máxima da curva, correspondente a 80 mm de chuva, indica que acima deste volume os conídios são precipitados do ar.Palavras-chave adicionais: queima das folhas, aerobiologia, epidemiologia. ABSTRACT Aerial dispersion of Lasiodiplodia theobromae in coconut plantationsThe objective of this research was to study the aerial dispersion of Lasiodiplodia theobromae, the causal agent of coconut (Cocos nucifera) leaf blight, and its relationship with pluviometric precipitation. Five wind catcher spore traps and one Burkard spore trap were installed in a coconut plantation, at a height of 1.80 m from the ground. The conidia were captured in transparent tapes covered with gelvatol and vaseline. Every week, the tapes were retrieved and mounted on slides for microscopy, where the number of trapped conidia was determinated. For the wind catcher trap, the highest amount of trapped conidia was 231 units in the month of October. For the Burkard spore trap the highest amount of captured conidia was 3072 units achieved in June. In general, during a-year-round sampling, there was a predominance of conidia liberation during the diurnal period. The highest amount of conidia was captured from 6:00 to 10:00 a.m. The number of conidia trapped by the two types of devices correlated positively with the amount of precipitation ranging from 25 to 80 mm. Above 80 mm of rain, the correlation was negative. Curves of tendency were established indicating that the...

Evaluation of dwarf coconut (Cocos nucifera L.) germplasm to the damage intensity caused by foliar diseases

“…This observation is in accordance with Warwick et al (1993), who observed significantly higher growth rate of lesions caused by leaf blight in coconut hybrids in the dry season. The anemophilic dispersion of L. theobromae conidia has been reported to be strongly stimulated by rainfall, especially between 25 and 80 mm of monthly average rainfall, according to monitoring in the coconut production field (Correia and Costa, 2005). In the present study, the period from October to March presented the most favorable monthly averages rainfall for spore dispersion, as reported by Correia and Costa (2005), which in a large extent coincides with the period of greatest damage caused by leaf blight.…”

Spatial-temporal Analysis of Gummosis in Three Cashew Clones at Northeastern Brazil

“…This tendency points out to the previous hypothesis that the pathogen is first introduced via randomly infected planting materials. Lasiodiplodia theobromae has been reported as an endophytic fungus (Baird and Carling 1998;Cilliers 1993;Mohali et al 2005;Mullen et al 1991;Rubini et al 2005) or as latent pathogen (Freire et al 2004;Khanzada et al 2004;Correa and Costa 2005;Cardoso et al 2009).…”

Hourly and daily changes on airborne urediniospores of Phakopsora pachyrhizi

“…However, in a study made in Manitoba, Canada, monitoring airborne-ascospores of Gibberella zeae, the maximum amount was collected at 9:00 pm (INCH et al, 2005). Correia & Costa (2005), noted that the period of spore release Lasiodiplodia theobromae occurred during the hours of 6:00 am to 10:00 am. Schuh (1993) reported that Cercospora kikuchii released spores between 4:00 am and 8:00 am and between 6:00 pm and 9:00 pm.…”