Fusarium Head Blight Of Wheat And Barley PDF Download

Fusarium head blight (FHB), primarily caused by Fusarium graminearum, is a top disease of concern to wheat and barley production, contributing to both yield losses and grain contamination across the United States (US). FHB is of particular importance to small grain production in the East Coast and Mid-Atlantic region, with widespread occurrence annually. F. graminearum is well adapted to the climate of the Mid-Atlantic; able to thrive during warm and wet conditions and able to infect wheat, barley, corn, beans, and other small grain crops. For many years, triazole/ demethylation inhibitor (DMI, FRAC Group 3) fungicides were the only group labeled for FHB. In 2019, Miravis Ace (Syngenta, Switzerland), was registered for use in the management of FHB, containing propiconazole (DMI) and pydiflumetofen, a Succinate Dehydrogenase Inhibitor (SDHI, FRAC Group 7). In vitro poison plate mycelial assays were performed on Fusarium isolated from wheat and malting barley to determine baseline sensitivities to pydiflumetofen. Wheat samples were submitted from 16 states and malting barley samples were submitted from three states as part of the United States Wheat and Barley Scab Initiative (USWBSI) National FHB Collection. In total, 177 Fusarium graminearum isolates from wheat were obtained across 2020 (n=98), 2021 (n=65), and from historic isolate collections ranging from 1991-2014 (n=14) with no exposure to pydiflumetofen. The effective concentration to reduce mycelial growth by 50% (EC50) was determined for wheat isolates using potato dextrose agar (PDA) Petri dish assays amended with pydiflumetofen to final concentrations of 0, 0.01, 0.05, 0.25, 1.0, and 5.0 Îơg/mL. Wheat EC50 values ranged from 0.18 to 0.73 Îơg/mL, averaging 0.4 Îơg/mL and 0.37 Îơg/mL, in 2020 and 2021 respectively. The average EC50 value of historic isolates was 0.35 Îơg/mL. Malting barley production has been expanding across the Mid-Atlantic. From 2020-21, malting barley isolates were collected to identify species diversity and screen for fungicide baseline fungicide sensitivity to pydiflumetofen. In the preliminary set of 28 barley isolates, 79% were identified as F. graminearum, 7% F. verticillioides, 7% F. acuminatum, 3.5% F. poae, and 3.5% F. asiaticum. Diversity of Fusarium species recovered from malting barley samples merits continued exploration. In vitro assays were conducted on amended yeast bacto agar (YBA) plates and a subset of isolates were also tested on amended PDA to compare growth. Media plates were amended with pydiflumetofen to final concentrations of 0, 0.01, 0.05, 0.25, 1.0, and 5.0 Îơg/mL. Average EC50 values for barley isolates on YBA were 1.09 Îơg/mL for F. graminearum (n=22), 1.07 Îơg/mL for F. verticillioides (n=2), 1.51 Îơg/mL for F. acuminatum (n=2), 1.09 Îơg/mL for F. poae (n=1), and 1.09 Îơg/mL for F. asiaticum (n=1). Isolates grown on YBA and PDA responded to treatment similarly, with EC50 values of 1.09 and 1.04 Îơg/mL, respectively. YBA-grown isolates experienced more uniform lateral growth and were more amenable to rating than PDA-grown isolates. The established baseline fungicide sensitivity levels in wheat and malting barley will aid fungicide research and allow for monitoring of sensitivity levels in F. graminearum populations in small grain production regions of the United States as SDHI fungicide use expands.