Sequential Post-Heading Applications for Controlling Wheat Blast: A 9-Year Summary of Fungicide Performance in Brazil

Abstract

Wheat blast, caused by Pyricularia oryzae Triticum (PoT) lineage, is a major constraint to wheat production, mainly in the tropics of Brazil where severe epidemics are more frequent. We analyzed disease and wheat yield data from 42 uniform field trials conducted during nine years (2012 to 2020) in order to assess whether the percent control and yield response were influenced by fungicide type, region (tropical or subtropical), and year. Six treatments were selected, all evaluated in at least 19 trials. Two fungicides were applied as solo active ingredients: MANCozeb, and TEBUconazole, and four were premixes: AZOXystrobin + TEBU, TriFLoXystrobin + PROThioconazole, TFLX + TEBU, and PYRAclostrobin + EPOXiconazole. Percent control, calculated from back-transforming estimates by a meta-analysis network model fitted to the log of the means, ranged from 43% to 58%, with all but PYRA + EPOX showing efficacy greater than 52% on average, not differing among them. The variation in both efficacy and yield response was explained by region and all but TEBU performed better in the subtropics than in the tropics. Yield response from using three sequential sprays was around two times greater in the subtropics (319 to 532 kg/ha) than in the tropics (149 to 241.3 kg/ha). No significant decline in fungicide efficacy or yield response was observed in nine years of study for any of the fungicides. Our results reinforce the need to improve control by adopting an integrated management approach in the tropics given the poorer performance and lower profitability, especially for the premixes, than in the subtropics.

A review on the potential effects of temperature on fungicide effectiveness

“…Thus, global warming can worsen disease damage through reduced chemical plant protection efficacy (Matzrafi, 2019), threatening food security. Indeed, presumably, contemporary environmental variability is already threatening efficacy of plant protection products including fungicides under field conditions, for example, under already humid and warm tropical conditions (Ascari et al, 2021) or in the summer under temperate climatic conditions. However, Table 1 shows that only a few experimental studies related to the effects of temperature on preharvest fungicide efficacy level and efficacy duration are available.…”

Taxonomic and pathogenic diversity of the blast pathogen populations infecting wheat and grasses in Minas Gerais

“…The trials were conducted in several locations and during nine years in Brazil by members of Cooperative Trials of Wheat (http://www.ensaioscooperativos.net/). The meta-analysis study showed no evidence of decline in fungicide efficacy over nine years (2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020) for any of the six fungicides evaluated (Ascari et al 2021). However, in vitro studies detected Brazilian blast population carrying mutation points that confer resistance to strobilurins and triazoles fungicides (Castroagudín et al 2015;Dorigan et al 2019;D' Ávila et al 2020;Poloni et al 2021).…”

“…(Rajiv 2017;Sadat and Choi 2017;Cruz and Valent 2017;Mottaleb et al 2018Mottaleb et al , 2019Ceresini et al 2018Ceresini et al , 2019Islam et al , 2020Kamoun et al 2019;Tembo 2019;Yesmin et al 2020;Mbinda and Masaki 2021, Singh et al 2021, Tosa 2021. While some aspects have been given more attention, such as the taxonomy and population genetics (Couch and Kohn 2002;Tanaka et al 2009;Luo and Zhang 2013;Maciel et al 2014;Murata et al 2014;Klaubauf et al 2014;Gladieux et al 2015Gladieux et al , 2018Castroagudín et al 2016;Valent et al 2019), chemical control (Kim et al 2003;Cruz et al 2011Cruz et al , 2019Pagani et al 2014;Rocha et al 2014;Castroagudín et al 2015;Oliveira et al 2015;Dorigan et al 2019;D'Ávila et al 2021;Ascari et al 2021) and host genetic resistance (Cruz et al 2016b;Anh et al 2018;Rocha et al 2019;Cruppe et al 2020;Inoue et al 2021;Dianese et al 2021;…”

“…Although all these control tactics are useful to minimize the risk of damaging epidemics, chemical control with fungicides is the last resort to manage the disease more effectively (Ceresini et al 2018(Ceresini et al , 2019Cruz et al 2019;Ascari et al 2021).…”

“…The efficacy of control of chemicals varied depending of the region, as wheat blast control and yield return were larger in subtropical climate than tropical conditions, differing by at least 18 percent points (40.6 to 58.9%) and 150.7 kg/ha (227.4 to 378.1 kg/ha), respectively. The best management strategy was spraying combinations of siti-specific and multi-site fungicides, with efficacy over 50%, such as mancozeb, trifloxystrobin + prothioconazole, tebuconazole, azoxystrobin + tebuconazole, and trifloxystrobin + prothioconazole (Ascari et al 2021).…”