Abstract
ABSTRACT To study the efficiency of Asian soybean rust (Phakopsora pachyrhizi) control and to test the effects of using alternative products and fungicides, two field experiments were conducted during the harvest seasons 2013/2014 and 2014/2015. Treatments for the experiments were: 1- control (water); 2- acibenzolar-S-methyl; 3- calcium; 4- micronutrients: copper, manganese and zinc; 5- micronutrients: manganese, zinc and molybdenum; 6- NK fertilizer; 7- Ascophyllum nodosum, and 8- azoxystrobin + cyproconazole. The evaluated variables were: Asian soybean rust severity, defoliation, productivity and yield components. Based on severity data, the area under the disease progress curve was calculated. In the two experiments, the alternative products had no effect on Asian soybean rust or defoliation. Only the treatment with fungicide controlled the disease and decreased defoliation. The yield component affected by the treatments was the number of pods per plant, in both harvest seasons. Treatment with the fungicide protected soybean from yield loss in both experiments. Defoliation was strongly correlated with the weight of one thousand seeds and the number of pods per plant, emphasizing the importance of maintaining the leaf area to ensure the maintenance of the yield components in soybean crop.
Highlights
Para estudar a eficiência do controle da ferrugem asiática da soja (Phakopsora pachyrhizi) e testar os efeitos do uso de produtos alternativos e fungicidas, foram realizados dois experimentos de campo durante as safras 2013/2014 e 2014/2015
Considering that Asian soybean rust is highly destructive, a commonly adopted management option is the use of fungicides, since cultivars fully resistant to this disease have not been developed yet (22)
The present study aimed to evaluate the effects of foliar application of alternative products on Asian soybean rust severity, defoliation, yield components and productivity of soybean plants in a non-tillage system in the harvest seasons 2013/2014 and 2014/2015
Summary
Two experiments with soybean crops were conducted in distinct harvest seasons (2013/2014 and 2014/2015), in the municipality of Ponta Grossa – Paraná State, Brazil, located at 25°13′ latitude, 50°03′ longitude, and 900 m altitude. The development of the soybean crop followed the phenological scale proposed by Fehr & Caviness (14), reviewed by Ritchie et al (27). In both experiments, four applications of each alternative product were performed in the phenological stages V3 (2nd developed trifoliate), V6 (5th open trifoliate), R1 (beginning of flowering), and R5.1 (grains perceptible to touch - 10% grain formation). Defoliation was evaluated when the plants of the control plot reached 80-85% defoliation, which was estimated based on the diagrammatic scale developed by Hirano et al (18). At the end of the crop cycle, when grain moisture was around 15%, the plants in the useful area of each plot were manually harvested. Pearson correlation coefficients (r) were determined for AUDPC, defoliation and yield components with the software STATISTICA®
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