Abstract
Dry rot of yam (Dioscorea spp.) caused by Scutellonema bradys and Pratylenchus spp. has restricted yam production in Brazil. Plant-based products can be useful reducing nematode damages. The objectives of this study were to evaluate the nematostatic and nematicidal in vitro activities of pyroligneous extracts from Cocos nucifera, Syagrus cearensis, S. coronata, and Wodetia bifurcata palms against S. bradys and to evaluate the effect of C. nucifera pyroligneous extract in the treatment of yam tubers infected by S. bradys and Pratylenchus sp. under greenhouse conditions. The pyroligneous extracts obtained at pyrolysis temperatures of 400, 500, 600, and 700 ºC, and at different concentrations, were tested for nematode immobility and mortality in Kline slides. Cocos nucifera pyroligneous extract obtained at 400 °C and 1% concentration was tested on yam tubers, under different immersion periods. Six months after yam planting the nematode populations were evaluated. All pyroligneous extracts inhibited the mobility and caused mortality to S. bradys, however 100% inhibition of both variables was achieved at concentrations varying from 0.75 to 2%, depending on the pyrolysis temperatures. The reproduction factor was reduced in 43% by treating infected yam tubers with pyroligneous extract from C. nucifera.
Highlights
Yam (Dioscorea spp.) production in Brazil has been affected by many factors; among these, the well-known dry rot disease, which is caused by the plant-parasitic nematodes Scutellonema bradys (Steiner & LeHew) Andrássy, Pratylenchus coffeae (Zimmermann) Filipjev & Schuurmans Stekhoven and P. brachyurus (Godfrey) Filipjev & Schuurmans Stekhoven
Significance was observed for all the products tested concerning the percentage of S. bradys immobility (PIM) and mortality (PMORT), depending on the concentrations and the pyrolysis temperatures (Table 1)
Results from the present study demonstrated that all pyroligneous extracts caused immobility and mortality to S. bradys, mostly independent of the pyrolysis temperatures
Summary
Yam (Dioscorea spp.) production in Brazil has been affected by many factors; among these, the well-known dry rot disease, which is caused by the plant-parasitic nematodes Scutellonema bradys (Steiner & LeHew) Andrássy, Pratylenchus coffeae (Zimmermann) Filipjev & Schuurmans Stekhoven and P. brachyurus (Godfrey) Filipjev & Schuurmans Stekhoven. The incidence of these nematodes produces symptoms of necrosis in the outer parenchymatous tissues of yam tubers, resulting in decreased productivity and depreciating the product quality (Moura, 2016). Several authors have searched for new alternatives to control the disease, including the use of plant extracts (Coimbra et al, 2006; Lima et al, 2019)
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