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39

Evaluation of soybean rust control with different fungicide application timing

Presenter: Donita Alencar Araripe Andrade(1)

Other authors and affiliations: Paulino José Melo Andrade(2). (1)Fundação Chapadão, Plant Pathology, Chapadão do Sul, MS 79.560-000, Brazil; (2)Embrapa Soja, Plant Pathology, Chapadão do Sul, MS 79.560-000, Brazil

This trial’s goal was to evaluate different fungicide application programs on soybean rust control. The cultivar was Msoy 8001, sowing at 01/24/2002, on a random design with four replications. The programs with pyraclostrobin + epoxiconazole 79.8 + 30.0 g a.i./ha were based on the first disease signs that appeared on growth stage R4: (i) spray started on R4 and repeated weekly, until 32 days after R4; (ii) started 8 days after R4 and repeated weekly until 32 days; (iii) 16 days and repeated weekly until 32 days; (iv) 24 and 32 days after R4; (v) 32 days after R4; (vi) four sprays, starting on R4 and ending on day 16; (vii) three sprays, starting on R4 and ending on day 16; (viii) R4 and 8 days after; (ix) R4; and (x) check. Disease severity was estimated for each leaflet of the principal stem. A 7-day delay on fungicide application after the disease detection resulted in an 82% defoliation increase and a 37% disease severity increase and reductions of 10 and 16% in seed weight and yield, respectively. When the delay was 14 days, the reduction percents were greater. Sprays started on R4, despite of the number of applications, were efficient on soybean rust control.

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