Efficacies and profitability of different fungicides and spray regimes for control of soybean rust (Phakopsora pachyrhizi Syd.) in Uganda

Abstract

Three fungicides: Dithane- M45 (contact wettable powder), Saprol and Folicur (both systemic), and three spray regimes, weekly. 2-weekly, and 3-weekly sprays from disease onset to full seed formation, were evaluated against soybean rust incited by Phakopsora pachyrhizi Syd. These corresponded to 5, 3, and 2 sprays, respectively. Nam 2 a highly susceptible variety was used in the study. The unprotected soybean had significantly higher rust severities (>75%) and lower yields (968 kg/ha) as compared to the rust-protected soybean, with rust severities < 70%) and yields (> 1000 kg/ha). Highest yield increase with Dithane, Saprol, and Folicur of 26.9, 33.3 and 38.9%, respectively were obtained under the weekly, 2-weekly, and 3-weekly spray schedules. The highest economic returns for Dithane (71, 252 Shs/ha), Saprol (127,607 Shs/ha), and Folicur (236, 181 Shs/ha), were obtained under the 2-weekly, 2-weekly, and 3-weekly spray schedules. Rust control was associated with increased seed weight and number of filled pods per plant.