Evaluation of foliar fungicides for the control of soybean late season diseases and rust in Tucumán, Argentina

PLOPER, L.D.,; GONZALEZ, V.,; RUIZ, S.,; GALVEZ, M.R.,; DEVANI, M.R.

Beijing, China

Conferencia; World Soybean Research Conference VIII; 2009

Institute of Grop Science, Chinese Academy of Agricultural Sciences

The late-season disease complex (LSD), a combination of various diseases that affect the foliage, stems, pods, and seeds during the mid- to late-reproductive growth stages, has been shown to cause significant yield losses in Tucumán and other provinces of northwestern Argentina (NWA).  Another disease that affects the foliage is soybean rust, caused by Phakopsora pachyrhizi.  Application of foliar fungicides is considered one of the most effective ways of managing these diseases under the current cropping conditions in NWA.  Extensive field evaluations of foliar fungicides have been carried out in Tucumán since the 1998-1999 growing season.  This report summarizes yield data from ten seasons, during which various active ingredients as well as the number and timing of fungicide application were evaluated.  In each trial, treatments were arranged in randomized complete blocks with four replications per test. Plots consisted of four 6-m rows, spaced 0.5 m apart.  Fungicides were applied with a CO2 backpack sprayer at stages R3, R5 or R6.  Double applications were evaluated during the first three seasons, and single applications in the remaining seasons.  Parameters evaluated included: % defoliation at R7, degree of stem colonization by LSD, rust incidence and severity, yield, 1000-seed weight, and % seed infection.  Fungicide treatments always had higher yields than the control, except in 2004-2005.  Yield increases ranged from 3 to 32%. No differences were detected between one and two applications. Yield response to fungicides was most highly related to cumulative rainfall between R1 and R3.