Performance of dual and triple fungicide premixes for managing soybean rust across years and regions in Brazil: A meta‐analysis

Abstract

Soybean rust in Brazil is currently controlled with several commercial fungicide premixes composed of demethylation inhibitors (EPOXiconazole, CYPRoconazole, PROThioconazole, TEBUconazole), quinone‐outside inhibitors (AZOXystrobin, TriFLoXystrobin, PYRAclostrobin, PICOxystrobin), and succinate demethylation inhibitors (BENZovindiflupyr, BIXaFen, FLUXapyroxad). Here, we summarize the performance of eight premixes evaluated in 177 cooperative trials conducted in 46 locations across 10 states from 2015 to 2020. All fungicide treatments were sprayed three times starting at R1/R2. Percentage control (trueC¯, %), from back‐transforming meta‐analytic estimates of the log of the ratio, ranged from 56.2% (PICO + CYPR) to 76.8% (BIXF + TFLX + PROT). Estimates of mean yield difference (trueD¯, kg/ha) between fungicide‐treated and untreated plots were greatest for BIXF + TFLX + PROT (1,080) followed by PICO + BENZ (1,010), PYRA + EPOX + FLUX (981.5), AZOX + BENZ (910), TFLX + PROT (891), PICO +TEBU (682), TFLX + CYPR (646), and PICO + CYPR (600). Significant declines in both trueC¯ and trueD¯ in as little as 4 years were detected for AZOX + BENZ (35.3%; 550 kg/ha) and PICO + BENZ (15.5%; 359.8 kg/ha). Variance in trueD¯ was reduced by the inclusion of baseline severity as covariate. In trials where baseline disease was ≥70%, yield was 250 kg/ha greater compared to areas with low baseline disease. Disease control and yield response were generally greater in the south‐east, where the frequency of profitable scenarios was 30% higher on average than in the north‐west. Results of this meta‐analysis are critical for supporting decisions during planning of fungicide programmes.

Major proliferation of transposable elements shaped the genome of the soybean rust pathogen Phakopsora pachyrhizi

“…The pathogen is highly adaptive and individually deployed resistance genes have been rapidly overcome when respective cultivars have been released 6 , 7 . Similarly, the fungal tolerance to the main classes of site-specific fungicides is increasing, making chemical control less effective 8 – 10 . Another remarkable feature for an obligate biotrophic pathogen is its wide host range, encompassing 153 species of legumes within 54 genera to date 11 – 13 .…”

The soybean rust pathogen Phakopsora pachyrhizi displays transposable element proliferation that correlates with broad host-range adaptation on legumes

“…The pathogen is highly adaptive and individually deployed resistance genes have been rapidly overcome when respective cultivars have been released ( 5, 6 ). Similarly, the fungal tolerance to the main classes of site-specific fungicides is increasing, making chemical control less effective ( 7–9 ). Another remarkable feature for an obligate biotrophic pathogen is its wide host range, encompassing 153 species of legumes within 54 genera to date ( 10–12 ).…”

Disentangling environmental effects on plant disease epidemics at the regional scale

“…Since the early years of dealing with the disease, major actions were taken to understand the disease, prevent its further spread, predict disease risk, and establish effective control measures, more notably in Brazil (Godoy et al 2016) and the United States (Allen et al 2014;Sikora et al 2014). In Brazil, a national "anti-rust" consortium named "Consórcio Antiferrugem"' was established in 2004, when efforts focused on monitoring the seasonal disease spread across the country as well as testing fungicides for disease control (Godoy et al 2016;Dalla Lana et al 2018;Barro et al 2021;Machado et al 2021). The initiative has been responsible for collecting, curating, and sharing data on the first SBR detections at the municipality level every growing season (http://www.consorcioantiferrugem.net).…”