Chemical control of asiatic soybean rust (Phakopsora pachyrhizi) in second sowing in Paraguay.

ABSTRACT

The aim of the present study was to evaluate the effectiveness of using different active ingredients and mixtures to chemically control Asian soybean rust in second crops in Paraguay. The experiment was conducted in the municipality of Katuete in the 2020 agricultural year. Experimental design was in randomized blocks with 8 treatments and four replicates. Evaluations started 7 days after the first application; all other evaluations were carried out at 14-days intervals. The evaluated variables were phytotoxicity, disease severity, area under the disease progress curve (AUDPC), control percentage, yield and yield reduction. Results underwent analysis of variance and were compared accordind to Tukey´s test at 5%, using SISVAR software. Leaf phytotoxicity was observed in all evaluations, and the highest percentage reached 25% with the prothioconazole and pyraclostrobin + prothioconazole mixtures. The combination of (picoxystrobin + prothioconazole) + mancozeb at doses of 600 + 1500 cc ha-1 provided the lowest disease severity, (7.41%), the lowest AUDCP (62.91) and a disease control rate of 92%. Positive effects of the fungicide treatments were observed on the yield, which had significantly higher increases, compared to the untreated control.

Keywords
Glycine max ; Fungicides; chemical control